Guideline on optimal architectures for crashworthiness and compatibility improvement

Transcription

1 Project nº D3.1 GUIDELINES ON OPTIMAL ARCHITECTURES FOR CRASHWORTHINESS AND COMPATIBILITY IMPROVEMENT Project Acronym: OPTIBODY Project Full Title: "Optimized Structural components and add-ons to improve passive safety in new Electric Light Trucks and Vans (ELTVs)" Grant Agreement No.: Responsible: Politecnico di Torino Internal Quality Reviewer: University of Zaragoza Version: 3 ( ) Dissemination level: Public SUMMARY: This report proposes guidelines for the improvement of the safety of ELTVs coming from the preliminary analysis carried out during the first year of OPTIBODY. The document is structured in four parts. First, definition of an ELTV according to the different regulations in the world is accounted for. The definition is also related to the choices made in OPTIBODY for the type of vehicle considered. The second chapter summarizes the current regulations and homologation requirements for the vehicles of types N1 and L7e where ELTVs fall into. This is propaedeutic to the following part, chapter 3, which collects the OPTIBODY proposals of safety tests for the evaluation of the ELTVs. Chapter 4 is a thorough analysis of the currently available safety systems for vehicle of various types. Based on this safety system analysis, proposals for updated safety systems more suitable for ELTVs are given in the last chapter.

2 INDEX 1. EXECUTIVE SUMMARY 5 2. HOMOLOGATION SAFETY REQUIREMENTS Category N Category L Light weight passenger vehicles (M1), and current crash safety homologation requirements European and U.S. New Car Assessment Program Australia and New Zealand (ANCAP) China (C NCAP) Latin America (Latin NCAP) PROPOSED CRASH TEST FOR NEW HOMOLOGATION REQUIREMENTS Frontal crash test Side crash test Insurance and rear crash test Whiplash injury criteria Rollover protection Pedestrian crash tests Summary of the proposed tests for ELTVs CURRENT SOLUTIONS ADOPTED TO ATTAIN THE REQUIRED SAFETY LEVELS Front part 31 Page 2 of 75

3 4.2. Side parts Body side Doors Underrun protections Cockpit Restraint systems Safety Belts Air Bag Dashboard and interior trims Seats Rear part PROPOSAL FOR IMPLEMENTATION OF SAFETY FEATURES ON ELTV Conceptual design of crumpling zone (front part) Force on the passenger Recommended materials used for crumple zone Side part Passenger compartment The Door The underrun and side crash protections Cockpit 57 Page 3 of 75

4 5.9. Restraint systems Rear Part REFERENCES APPENDIX - ANALYSIS OF CURRENT VEHICLES BEHAVIOUR IN WHIPLASH Analysis of AGU database Study: Acceleration pulses and crash severity in low velocity rear impacts real world data and barrier tests Biomechanic analysis of whiplash injuries Dummy model Validation Model of vehicle cabin Conclusions 75 Page 4 of 75

5 1. Executive summary This report proposes guidelines for the improvement of the safety of ELTVs coming from the preliminary analysis carried out during the first year of OPTIBODY. Further improvements in these guidelines and in the possible safety outcome will be available at the end of the project. Safety of ELTVs is addressed in terms of two fundamental topics: The safety features able to guarantee required safety standards The regulations o directive that state these requirements and the methods to verify or certify fulfilment of required standards For both topics, the current status has been first analysed by examining existing standard or current state-of-the art safety features of LTVs or other types of vehicles, then proposals for updates and adaptations to the characteristics of ELTVs are illustrated. The current status is that, differently from normal vehicles, for passengers or goods transportation, light vehicles are characterised by very limited or null safety characteristics. Safety standards are also nearly absent. To improve safety of ELTVs it is necessary to first analyse, and then take into account of their peculiarity in terms of characteristics and usage: they are light vehicles, to be used mainly in urban areas, and at low speed. Because of this, lower masses and lower speeds must be considered in safety verification and homologation. This said, since the weight of these vehicles is relatively low and their price comparatively small, or it should be, hopefully to increase their spread onto the market, safety features must also be adapted. Sufficient safety taking into account the previous considerations can be obtained, to the OTIBODY s community knowledge acquired, at two levels. First, driver/passenger protection should be guaranteed by a series of adapted restraint devices; second, the vehicle structure should be built with chassis parts and add-ons able to assure sufficient cabin strength, to protect the driver/passenger, and limit aggressiveness to VRU s. The document is structured in four parts, more or less following the described concepts. First, definition of an ELTV according to the different regulations in the world is accounted for. The definition is also related to the choices made in OPTIBODY for the type of vehicle considered. The second chapter summarizes the current regulations and homologation requirements for the vehicles of types N1 and L7e where ELTVs fall into. This is propaedeutic to the following part, chapter 3, Page 5 of 75

6 which collects the OPTIBODY proposals of safety tests for the evaluation of the ELTVs. Chapter 4 is a thorough analysis of the currently available safety systems for vehicle of various types. Based on this safety system analysis, proposals for updated safety systems more suitable for ELTVs are given in the last chapter. The work carried out in WP3 can be considered, in the authors opinion, a very sound and well founded framework to achieve improved safety in ELTVs. This is established by providing methods (well suited testing methodologies for assessing an adequate reasonable level of safety) and tools (definition of various safety features on the basis of the adaptation of existing components to the requirements of lightweight of ELTVs). Final verification of the validity of such results will be, however, attained only at the end of the project, once the prototype either virtual or physical will be available, and every check will be made, end, eventually, one OPTIBODY s concepts will be on the road Objectives and scope of this document In the DOW WP3 will address free spaces reallocation, lightweight design and significant weight redistribution that will cause remarkable changes to the behaviour of the vehicles in case of an impact, and will affect the design of all the safety features so to give guidelines to achieve, at least, the standard ratings nowadays required for safety. Links are established with other WPs since In order to achieve the objectives, information coming from three partners (UNIZAR, CZ, IDIADA) with a constant activity related to traffic accident investigation will be required. Since these three partners keep a close relationship and collaboration agreements with traffic safety Spanish administrations (national and regional), detailed data about urban accidents (including injuries and material damage) will be available to the Consortium. Data were obtained in WP1 and reported in D1.1 and D1.2. To achieve these goals three tasks were defined: Task 3.1 Passive safety requirements for front, side and rear impact protection Task 3.2 Passive safety requirements for rollover protection Task 3.3 Passive safety requirements for pedestrian protection and other vulnerable users Page 6 of 75

7 And a first report, deliverable 3.1, has to give detailed guidelines to obtain improved crashworthiness. At the end a second deliverable, D3.2, will evaluate the results from WP3 in terms of practical application, usability and constraints. The current deliverable addresses the whole three topics: from the investigations and analyses carried out, it has been found that some of these topics are of greater importance and require more attention (in terms of both safety features and their testing) whereas for others, like rollover, simple adaptation of current standards is sufficient Acronyms and glossary ELTV... Electric Light Truck and Van LCV... Light Commercial Vehicle NCAP... New Car Assessment Program RCAR... Research Council for Automobile Repairs MDB... Moving Deformable Barrier (also referred as Movable or Mobile) ODB... Offset Deformable Barrier HIC... Head Injury Criterion NIC... Neck Injury Criterion Whiplash... range of injuries to the neck caused by or related to a sudden distortion of the neck associated with extension, commonly associated with motor vehicle accidents, mostly when the vehicle has been hit in the rear but also in many other ways A-pillar... the foremost vertical column of the cabin, determining its lateral shape and supporting the roof and door/windows B-pillar... the central vertical column of the cabin, determining its lateral shape and supporting the roof and, usually behind front door. For commercial vehicles it can be the back column Bonnet... the component covering the front part of the vehicle (usually containing the engine while using an ICE, also known as the hood in American English) Chassis... framework supporting the remaining components/subsystems, having structural but also energy absorption functions Trolley... a moving carriage with ballast mass pushed against the tested vehicle in a crash test to simulate the impact of a typical vehicle Page 7 of 75

8 Front rail... the frontal longitudinal part of the chassis serving as support for components in the front part and with the main functionality of energy absorption in the case of a frontal crash: it can be considered as divided into two parts, the more advanced crash box collapsing at a lower load for the low speed impact considered in the insurance tests, and the rearward part, stronger, for the high speed impacts in crash Crash box... the part, usually advanced, of the front rail that should collapse at a relatively low force to absorb energy in a controlled way R point... the point on the SAE habitability dummy (usually 50 percentile male) which identifies the right position of the occupant corresponding to his knuckle joint between the femur and the hip. This point represents the main reference for the habitability design of a car S point... effective upper anchor point of the seat belt L points... effective lower anchor points of the seat belt Interior trim... the interior package, mainly for aesthetic purposes Add-on... a component added to the main chassis, either as integral part of a new vehicle or as a retrofit in the aftermarket Crumple zone... a structural feature used in vehicles designed to absorb the energy from the impact during an accident by controlled deformation of structure. It is sometimes an add-on and integrates the functionality of the front rails to improve safety Foam... an inhomogeneous material with a large fraction of voids to increase the energy absorption capability with low strength and light weight (also called cellular material) Cockpit... the ensemble of the cabin with all the parts herein contained or the overall volume inside the cabin Dashboard... the control panel placed in front of the driver of a vehicle, housing instrumentation and controls for operation of the vehicle (also known as also called dash, instrument panel, or fascia) 2. Homologation safety requirements Homologation relates directly to the type of vehicle: ELTVs are Electric Light Trucks or Vans homologated as N1 vehicles and, in Europe, also classified under the L7 category, according to the Directive 2002/24/CE. Page 8 of 75

9 Nowadays based on significant increase in demands, many car manufacturers have recently started to take interest into this market segment, but the majority of these small vehicles are still manufactured by smaller companies, at a low cost and with little or no research done on vehicle safety. This is probably due because there are still no legal requirements on crash testing for this type of vehicles. Type-approval requirements for new vehicles in the L category, defined in Directive 2002/24/EC1 can be divided in two main parts: vehicle requirements and user requirements. The vehicle requirements establish whether the vehicle fulfils all structural, performance and safety regulations required in order to be registered as a motorized road vehicle according to European law. The user requirements are dictated by licensing regulations, which include minimum allowed user age and the maximum allowed vehicle performance level that the user is allowed to handle. For what concerns the vehicle requirements, from the homologation safety requirements point of view, it is necessary to examine separately the N1 and the L7 categories of vehicles Category N1 The N category vehicles are used for the carriage of goods. They are subdivided in different subcategories. In particular the N1 vehicles have a maximum mass not exceeding 3.5 tonnes. These vehicles are also commonly called light commercial vehicles (LCV). Vehicles which qualify in this category are pickup trucks, vans and three-wheelers, all commercially based goods carrier. The LCV concept was created as a compact truck and is usually optimised to be ruggedly built, have low operating costs and powerful yet fuel efficient engines, and to be utilised in intra-city operations. For the homologation in EU, also these vehicles generally follow the regulations 661/2009. For what concerns the safety requirements, for the front impact, three different types of tests for the cabin, according to the UNECE29 regulation, are mandatory. The tests regard: Test A: frontal impact test intended to evaluate the resistance of a cab in frontal impact accident (Figure 2.1) Test B: an impact test to the A-pillars of the cab intended to evaluate the resistance of a cab in a 90 rollover accident with subsequent impact (Figure 2.2) Test C: a cab roof strength test intended to evaluate the resistance of a cab in a 180 rollover accident (Figure 2.3) Page 9 of 75

10 In these tests a certain mass with defined shape and dimensions impact against the cabin, as shown in Figure 2.1, and the survival space for the occupants is evaluated, which is the cabin will not undergo deformation dangerous to the occupants. Figure 2.1: Front impact test (test A) Page 10 of 75

11 Figure 2.2: Front pillar impact test (test B) Page 11 of 75

12 Figure 2.3: Roof strength test (test C) For what concerns the side impact, the homologation tests have been established with the regulation UNECE95, while, for the pedestrian impact, for vehicles up to 2.5 tons, the regulation applied is the 2003/102/CE Category L7 Light-weight vehicles are divided in vehicle categories based on requirements on vehicle mass and engine performance. These categories are dictated by European Commission directives [1-3]. For what concerns the L7 category, they are quadricycle with four-wheeler with a maximum unladen mass of 400 kg or 550 kg for a goods carrying vehicle. The maximum net power allowed is 15 kw. In addition to these categories there are geometrical requirements such as a maximum length of four meters, width of two meters for three- and four-wheelers. The height is set at a maximum of two and a half meter [2]. For all of the above, the mass of batteries shall not be included for electrically powered vehicles. Page 12 of 75

13 There are no legal requirements today concerning crash testing for the approval of motorcycles similar to those of cars, but there are regulations that specify mandatory safety characteristics of vehicle parts [3]. These vehicle characteristics include specific safety requirements for parts like seat belts, windscreens, and mirrors etcetera. It has to be mentioned that these types of vehicles is not a part of the Whole Vehicle Type Approval (ECWVTA) directive, and thus is not required to fulfil the regulations on which Euro NCAP is based upon. For the present; any crash testing similar to those conducted by Euro NCAP has to be made on the manufacturer s initiative Light weight passenger vehicles (M1), and current crash safety homologation requirements A briefly summary of testing methods and current crash safety homologation requirements are presented in the table 2.1. Country Technical Regulations Testing method Frontal crash standard(fmvss 208) Full-wrap impact against a rigid barrier at 35 mph (approx. 56 km/h), etc. Side impact standard(fmvss 214) Impact against a moving barrier at 50 km/h USA Side collision test against a pole (against a Pole Side impact(fmvss 201/ FMVSS 214) pole at 29 km/h) Rollover crash (FMVSS 216) Roof strength test Offset impact against a 70% overlap Rear impact standard (FMVSS 301) deformable barrier at 50 mph (approx. 80 km/h) RCAR-IIWPG Seat/Head Restraint Head restrains (FMVSS 202) Evaluation Protocol (simulated a 16 km/h rear impact) Offset impact against a deformable barrier at Frontal crash standard(ece R94) 56 km/h Side impact standard(ece R95) Impact against a moving barrier at 50 km/h EU Side collision test against a pole (against a Pole side impact (FMVSS 214) pole at 29 km/h) Bumper test (ECE 42) Impact against a rigid barrier at 4 km/h Head restrains (ECE 25) RCAR-IIWPG Seat/Head Restraint Evaluation Protocol (simulated a 16 km/h Page 13 of 75

14 rear impact) Impact on legs against bumper at 40 km/h Pedestrian protection(regulation(ec) Impact on the head against bonnet at 78/2009) 35 km/h Full-wrap impact against a rigid barrier at Frontal crash standard(adr 69) 48 km/h Frontal crash standard(adr 73) Based on ECE R94 Side impact standard(adr72) Based on ECE R95 Australia Pole side test (FMVSS 214) Rear impact standard (ADR22) Side collision test against a pole (against a pole at 29 km/h) Based on SAE J826 Based on ECE R25 Rollover crash (FMVSS 216) Roof strength test (Based on FMVSS 216) Japan Frontal collision standard (Article 18, Safety Regulation for Road Vehicles) Frontal collision standard (Article 18, Safety Regulation for Road Vehicles) Side collision standard (Article 18, Safety Regulation for Road Vehicles) Rear crash (Triass 33) Pedestrian Protection (Article 18, Safety Regulation for Road Vehicles) Seatbelt reminder (Article 22-3, Safety Regulation for Road Vehicles) Full-wrap impact against a rigid barrier at 56 km/h Based on ECE R94 Based on ECE R95 Full-wrap impact against a rigid barrier at 50 km/h Impact on the head against bonnet at 32 km/h Based on ECE R16 Table 2.1: Testing method for other countries However crash tests for vehicles on the main markets of the world are most often tested according by different New Car Assessment Program (NCAP), introduced by the National Highway Traffic Safety Administration (NTHSA) in the U.S in This program has branched into several regional programs: Australia and New Zealand (ANCAP), Latin America (Latin NCAP), China (C-NCAP) and Europe (Euro NCAP) [4]. These tests are not mandatory, so vehicles are either tested on initiative by NCAP association or by the manufacturers themselves, because they are important marketing key. Usually the tests used are based on the requirements for making a vehicle legal for sale within Page 14 of 75

15 the considered country. The NCAP performance requirements are higher than those described in the directive for homologation, and are constantly increasing to inspire safety improvements. A summary of those assessment program tests is presented in the following European and US New Car Assessment Program The crash tests conducted by Euro NCAP are [5-10]: Frontal impact into a deformable offset barrier at 64 km/h. MDB to car side impact into the driver s door at 50 km/h. Pole side impact into rigid pole at 29 km/h. Pedestrian impact at 40 km/h. Rear impact whiplash injury test These tests include child protection tests [11] and the implementation of active safety assisting equipment like electronic stability control (ESC), seat belt reminders, speed limitation devices and anti-lock braking systems (ABS) [12]. For what concerns the U.S. NCAP, as shown in Figure 2.4, the typology of crash tests proposed in this protocol are similar to the Euro NCAP ones, however changing some details. For example the front impact is against a rigid barrier with 100% overlap, at lower velocity, and in the side and pole impact, the direction of impact is slightly different Australia and New Zealand (ANCAP) The Australasian New Car Assessment Program (ANCAP) conducts crash tests and associated assessments in accordance with the test protocols issued by Euro NCAP and uses the following 4 internationally recognized crash tests for the assessment [13]. Frontal impact into a deformable offset barrier at 64 km/h MDB to car side impact into the driver s door at 50 km/h Pole side impact into rigid pole at 29 km/h Pedestrian impact at 40 km/h Page 15 of 75

16 Figure 2.4: Overview of NCAP crash tests [14] 2.6. China (C-NCAP) The experience of other countries indicates that the implementation of NCAP system can remarkably improve the safety performance of automobiles and road traffic safety. Therefore, on the basis of fully studying and borrowing from the NCAP development experience of other countries, China Automotive Technology and Research Center (CATARC) has developed the C-NCAP, or China New Car Assessment Program, allowing for China s automotive standards, and technological and economic development conditions and conduct the following testes for the newly manufactured vehicles [15]. Frontal impact test against a rigid barrier with 100% overlapping at 50 km/h Page 16 of 75

17 Fontal impact test against the deformable barrier with 40% overlapping at 64 km/h Side impact test against the mobile deformable barrier at 40 km/h Whiplash test at km/h 2.7. Latin America (Latin NCAP) Latin NCAP is a new program, which started with the frontal impact tests. As stated on UN regulation 94, the frontal impact test is a key safety test for vehicles which provides sufficient evidence to be able to make a judgment on the safety of a vehicle and risks to car occupants. Therefore, Latin NCAP conduct only frontal impact test with deformable offset barrier of 40% overlap at 64 km/h. Page 17 of 75

18 3. Proposed crash test for new homologation requirements The design of electric vehicles differs significantly from conventional vehicles in terms of mass, structural components and battery pack mass. There is a need to ensure that the resulting vehicle package affords the same level of safety as conventional vehicles, with also particular attention on structural integrity of battery. Safety design is performed on the basis of selected accident scenarios. Based on the current state-of-the-art of vehicles safety also for the electric vehicles [16], and on the experiences made throughout the recent European Research Projects on safety (namely APROSYS, and ADVANCE) and the current regulations on safety and consumer tests procedures (mainly Euro NCAP and US-NCAP, but also other relevant testing protocols such as J-NCAP and AUS-NCAP) a series of tests have been selected as new safety standards for the L7e (and equivalent) vehicles. It has been recognized, in fact, that there is a need to provide more safety for this class of road vehicles. The test methods suggested for urban light-weight vehicles are additions, or replacements, to current crash test methods. After a thorough analysis of the accident data, of the vehicle characteristics, of the market goals for these vehicles, and all the pros and cons connected with imposing safety and other requirements, and after in-depth discussion on the problem, a proposal for vehicle testing has been defined. Moreover, a two-level approach is also proposed: Tests at the component/sub-system level (mainly experimental) Tests at the vehicle (experimental or virtual) The option of allowing homologation by virtual testing is proposed, due to the high quality level of the current crash simulations. At the vehicle levels it is proposed to adopt a series of tests similar to the ones performed on N1 and M1 vehicles with proper adaptation. In the following, the main types and characteristics of the proposed tests are illustrated. Requirements for adequate safety levels to be met are not defined in details, but they will follow well established practice in vehicle safety (such as the use of limiting forces, acceleration, and injury criteria like HIC, NIC and so on). Page 18 of 75

19 3.1. Frontal crash test Frontal impact is intended to represent the most frequent type of road crash, resulting in serious and fatal injuries. A number of test types have been used by the different organizations in the past to evaluate the vehicle performance in frontal crashes like car-to-car; car-to-fixed barrier, moving barrier-to-car, and car-to-narrow objects crash tests. Nowadays, this test has narrowed to two types: the full frontal impact test against a rigid barrier with 100% overlapping and the frontal impact test against a deformable barrier with 40% overlapping. ELTVs are planned for the carriage of goods mainly in urban areas, due to their limited range. Therefore, and also depending on the limitations in terms of maximum power in Europe or speed in US, their top speed is rather limited. In their urban environment, the speed of other vehicles potentially having accidents with ELTVs, will be also limited (in theory to 50 km/h in Europe and 30 mph in the US and other countries using the imperial measurements system). Therefore, the impact speed that is most likely to occur in an urban impact is much less than 50 km/h. From the analysis of the accident data in WP1, as well as previous analyses and experiences of APROSYS SP2, it has been resolved that 35 km/h is a reasonable impact speed for the verification of ELTVs in car-to-eltv impact, and 25 km/h for the impact to fixed obstacles. This is because, before impact, emergency braking takes place in most cases. Moreover, additional safety can be obtained only at the cost of heavier and more expensive safety features not allowable for these vehicles. These impact speeds are proposed for the OPTIBODY tests. In order to have a full understanding of the frontal crashworthiness scenario, it is proposed and planned to conduct both full frontal impact test against a rigid barrier with 100% overlapping (Figure 3.1) and frontal impact test against a deformable barrier with 40% overlapping (Figure 3.2), with a velocity of 25 km/h and 35 km/h respectively. For both full frontal and offset test, Hybrid III test dummy, positioned and specified as Euro NCAP protocol [5] is used in the driver s position. Page 19 of 75

20 Figure 3.1: Full frontal impact test against a rigid barrier with 100% overlapping Figure 3.2: Frontal impact test against the deformable barrier with 40% overlapping 3.2. Side crash test Protecting people during side crashes is a challenging task, because the sides of vehicles have relatively little space (Figure 3.3 on the left) to absorb energy if compared to the front and rear parts of vehicles. Car-makers have made big strides in side protection in recent years by installing side air-bag and strengthening the vehicles structure (Figure 3.3 on the right). Side air-bags, which today are standard on most new vehicles, are designed to keep people from colliding with the inside of the vehicle and with objects outside the vehicle in a side impact. They also help by spreading impact forces over a larger area of an occupant body. However, side air-bag by themselves are not enough. Strong structures that work well with the air-bag are also crucial. Page 20 of 75

21 Figure 3.3: Example of little space between door and occupant on the left, example of side air-bag on the right For the ELTV design project, a side impact test at a velocity of 35 km/h with a 750 kg trolley mass is proposed. The trolley is similar to the one used for the crash test according to the Euro NCAP protocol [6], but the mass is reduced. The proposed test is planned not only to verify the cabin part of the truck and their occupants, but it also include parts of battery compartment in order to prevent the possible electric hazards and possible vehicle burn out during side crash. For this reason, as shown in Figure 3.4, the longitudinal axis of the trolley is positioned in the middle between the cabin structure and the rear part of the vehicle. To measure the injuries to the driver, a EuroSID-2 test dummy, positioned as specified in Euro NCAP protocol [6] is suggested. In this case also, reduced testing speed and reduced mass are proposed owing to the same considerations as for the front impact tests. The pole impact test is discarded due to the usual environment in which the ELTVs would be used (urban areas). In urban areas most pole-like objects (lamp posts, traffic lights, etc.) are relatively weak structures: except a few cases, usually far from the road or protected by barriers or other guards, they are small diameter and small thickness tubes not able to cause severe damage to a vehicle; instead, they usually collapse under a heavy mass impact. The problem with pole impact is mainly with trees or other plants mainly occurring in the countryside. Trees in urban areas are either small sized, or protected by barriers or separated by sidewalks, or in places like gardens or parks not directly accessible by vehicles. Page 21 of 75

22 3.3. Insurance and rear crash test Figure 3.4: Side crash test set-up It is estimated that in the European Union over 300,000 people each year suffer whiplashassociated injuries resulting from traffic accidents. The whiplash-associated injuries account for approximately 60% of all injuries caused by traffic accidents. Every day more advanced protection systems are being introduced in current vehicles so has been important to evaluate the effectiveness of these new systems. Clearly, any development of a system that offers protection for vehicle occupants against a rear impact should involve an analysis of the main variables that influence the possible appearance of injuries associated with such impacts. Some of the variables that influence the production of whiplash are gender, age and position of the vehicle occupant. From the point of view of design of the vehicle, parameters such as the geometry of seats and type of headrest are essential. The severity of the impact obviously influences the production of whiplash and will normally be determined by the variation of the speed and the average acceleration suffered by the struck car. Currently, testing protocols for assessing protection against whiplash use a combination of pulses to be applied on the test sled on which is mounted a seat with its corresponding dummy. Page 22 of 75

23 Among these protocols (mainly used by the RCAR and Euro NCAP), Euro NCAP is using a greater variety of pulses, a total of three, ranked by severity into low, medium and high. The pulses used by Euro NCAP have been adopted to represent those impacts that cause an increased risk of neck injuries, both short and long term, and to cover the most representative in terms of real situations. Since the pulses are part of the parameters set, the test criteria should be observed as evaluation criteria of vehicle seat against whiplash, but not the vehicle itself. The acceleration experienced by the occupant during a rear impact influences the severity of injuries associated with whiplash. While it is true that in the process of designing the structure of a vehicle are many factors to consider, a development effort in their structure which allow an increased absorption of energy, increasing and controlling the deformation to apply the solicitation during a longer time, will reduce the accelerations sustained by the occupants and hence the risk of whiplash injuries associated would be reduced. The development of a new ELTV without the current restraints is a good opportunity to take into account also the vehicle stiffness, in order to provide better protection to occupants in rear impacts Whiplash injury criteria Since the ultimate goal is to protect occupants against whiplash, it is necessary to review what is the injury criterion more widely disseminated on the scientific community WAD (Whiplash Associated Disorders) One of the criteria used to describe injuries associated with whiplash is the WAD criteria, created by the Quebec Task Force [17]. According to this classification, whiplash-associated injuries can be divided into: Page 23 of 75

24 Table 3.1: The Quebec classification of Whiplash Associated Disorders Mean acceleration and variation of speed. Folksam's study "Influence of crash severity on various whiplash injury symptoms: a study based on real-life rear-end crashes with recorded crash pulses" is considered one of the most important and accepted by the scientific community related to the analysis of the probability of injuries associated with whiplash in terms of acceleration and speed variation experienced by the vehicle. The results of the study to the expected duration of symptoms and also according to the degree of injury WAD, are summarized in the following graphs. Page 24 of 75

25 Figure 3.5: Various cases of injury risk evaluated for whiplash NIC (Neck Injury Criteria) The NIC measures the load on the neck occurs before contact with the headrest. The injuries were classified according to the duration of whiplash symptoms, if symptoms last more or less than one month. There is a correlation between the NIC and the risk of injury. This injury criterion is based on the following formula: Where: NIC = 0.2 a rel + v rel 2 a rel : relative acceleration in x direction between T1 and occipital joint v rel : relative velocity in x direction between T1 and occipital joint Page 25 of 75

26 The maximum NIC is the maximum value of the curve for the first NIC 150 ms (retraction phase). In order to avoid injuries associated with whiplash, the NIC max must be less than 15 m 2 /s 2. At lower values, the probability of whiplash injuries with lasting symptoms is low. Figure 3.6: Risk associated with the NIC level Insurance tests are also of great importance, and are suggested for the new ELTVs. In this case the frontal impact is not the only one: the rear impact is also of great concern. As a matter of fact, as done in other regulations (RCAR), the impact against a rigid barrier is the most common and also the most significant. The difference between insurance test and safety tests is the much lower speed, which is 15 km/h. Moreover, because these vehicles work in the urban scenario, it is recommended to take into consideration also the whiplash [7] phenomenon due to rear impacts. The most common injuries due to rear collision at low speed are related to the neck and are caused by sudden flexion and extension of the neck. The performance of a vehicle seat back in rear impact accidents can significantly affect occupant kinematics and resulting injury. To evaluate these injuries the set-up of the proposed test (Figure 3.7) is a rear impact with deformable trolley at 15 km/h. To measure the injuries to the neck, the Bio-RID dummy is used according to the Euro NCAP protocol [9]. Page 26 of 75

27 3.4. Rollover protection Figure 3.7: Vehicle rear impact to study whiplash injuries For this kind of vehicles rollover is not occurring frequently neither is critical for safety. The relatively low speed guarantees against the occurrence of serious rollover accident. However, a simple test how it is already performed on commercial vehicles is proposed. The current test is a static test performed by applying a prescribed force on the top of the cabin structure. The proposal is to simply keep the test illustrated in 2.1 by considering a lower force. Since ELTVs have fairly lower mass if compared to regular vehicles for the carriage of goods, it is proposed to consider a test force proportionally reduced. The allowed overall mass for N1 vehicles is 3500 kg, whereas is 550 kg for L7e vehicles excluding battery: this leads to nearly 900 kg with batteries, according to the weight breakdown coming from the analysis in WP5. Thus, a ratio of 4:1 is estimated. A reduction of 1 to 4 with respect to the requirements imposed by UNECE29 is proposed Pedestrian crash tests As one of the goals of OPTIBODY project is the improvement of pedestrian safety, in order to increase the current level of safety standards, also in this case the proposed tests share similar philosophy of the ACEA and Euro NCAP pedestrian safety tests. It was decided, however, to reduce the number of tests both to reduce the number of mandatory tests to be acceptable for vehicles that are less expensive than normal cars, and because some pedestrian tests have been demonstrated to be less critical in terms of damage to people of any age (from evaluations carried out in APROSYS SP7 [18] and other recent results [19]). The proposed tests are: Pedestrian head impact test (adult, at a lower speed, 35 km/h, than in Euro NCAP protocol [10]) Lower leg impact tests (at the same lower speed of 35 km/h) Page 27 of 75

28 Requirements for adequate safety levels to be met are not defined in details, but they will follow well established practice in vehicle safety (such as the use of limiting forces, acceleration, and damage index like HIC, NIC, and so on). The biggest difference between the suggested urban vehicle crash tests and the present car crash test program is that much more emphasis has to be taken to protect crash victims outside the vehicle, such as pedestrians, cyclist and motorcycle users. One possible way to encourage vehicle manufacturers to protect the vulnerable road users could be to change the current weight of crash test results. Today 70% of the total score comes from adult and child occupant protection assessment, and only 20% from pedestrian and cyclists protection assessment. Increasing the effect from getting good pedestrian test scores could be one possible solution in promoting better pedestrian protection for urban vehicles Summary of the proposed tests for ELTVs The tests illustrated up to now are at the full-vehicle level. A multiple level approach (as in APROSYS SP7) can be proposed. A second component level testing can be outlined and, in this case, some physical test could be performed. To demonstrate the validity of the adopted solutions, some tests can be proposed. For example: On the side for the driver protection: quasi-static strength evaluation with a 10 kn load On the frontal add-on for pedestrian protection; 30 km/h In the following Table 3.2 the proposed crash test for the ELTV vehicles are summarized. Page 28 of 75

29 40% offset Deformable barrier 35 km/h FRONT IMPACT Full frontal Rigid barrier 25 km/h SIDE IMPACT 35 km/h 750 kg trolley Table 3.2(1): proposed impact test scenario for ELTV vehicles. Page 29 of 75

30 Full frontal Rigid barrier INSURANCE CRASH TEST 15 km/h Full rear Rigid barrier 15 km/h Full rear REAR IMPACT Trolley 750 kg 15 km/h Head impact test PEDESTRIAN CRASH TEST 35 km/h Lower leg impact test 35 km/h Table 3.2(2): proposed impact test scenario for ELTV vehicles. Page 30 of 75

31 4. Current solutions adopted to attain the required safety levels In order to better understand which are the solutions adopted nowadays, on passenger vehicles and good transportation vehicles, to meet the requirements in terms of passive safety; the body of a vehicle can be divided in different sections [20]: Front part Side part Cockpit Rear part 4.1. Front part The front section of a vehicle is made of many different parts that contribute in different ways to the safety of the vehicle. The front frame is the assembly between the firewall and front bumpers. For most cars, this frame surrounds and supports the power train and its auxiliaries. Moreover, fitted to the front frame are the front suspension links, steering box, part of the air conditioning system and front lamps. Last but not least, the front frame is in responsible for absorbing front crash energy, impact loads together with the compartment frames (body side and floor) and for attenuating potential injury to vulnerable road users as pedestrians in the event of an impact. If the boundary cabin frame has been conceived to be a strong cage, these functions could be satisfied, for instance, using a cantilever embedded in the cage, with an increasingly strong section from bumpers to firewall, equipped with brackets to support the different various mechanical subsystems, and sufficiently far from the critical area to avoid direct contact with vulnerable road users during impact (Figure 4.1). Page 31 of 75

32 Figure 4.1: Main load position on the front frame (MP: power train; SP: suspension and steering; FE: front end; CR: crash) However, this simple scheme must comply with other requirements such as volume and obstruction restrictions, and enable operation of the different subsystems, and ensure the wheel motion envelope. Moreover, such a cantilever should be connected to a resilient compartment boundary frame (for example, the body side or floor members) and not directly to a wall such as the firewall for example. This is not only due to the extremely high loads (hundreds of thousand newton) to be faced during front impact, but also to avoid the fact that a cantilever bending could excite vibrations of the firewall and floor, giving raise to air pumping and noise within the compartment cavity. Many configurations of front rails embedded in the compartment cage can be found (Figure 4.2). In practice, all known configurations are a combination of basic members, shown in view (1) of Figure 4.2, with additional members that could be longitudinal, as in case (3) of same figure, cross members as in case (2), tilted as in case (4) and (5) or parallel to tunnel as in case (6). Front rails P, mainly responsible in front crash handling, are connected to upper shorter rails R, by vertical strut towers D, where the spring and shock absorber housings are located. The assembly of these three members which are always present is the structural block supporting the wheels vertical, longitudinal and side loads. The front rails P, that in Figure 4.2 appear to be straight and with constant section, often have a twisted axis and variable section both in the planar and lateral view, caused by the space restrictions due to the mechanical parts and their operation, in particular the suspensions, steering system and transmission links displacement. Therefore respective impact tuning is very difficult and the different allowable section configurations (circular, squared, rectangular, hexagonal) do not each exhibit the same energy absorption effectiveness. The proportion of energy absorbed by each member is shown in Figure 4.3. Page 32 of 75

33 Figure 4.2: Archetypes of front frame connections with compartment frame: real life frames are combinations of these archetypes. Lower front rails P are always present, between the power train and wheels, as far as upper front rails R, strut towers D that connect both rails, sills L and front seats cross-member TS Figure 4.3: Contributions of front frame single members in terms of front crash energy absorption EA. A) impact at 56 km/h against offset rigid barrier - Auto Motor und Sport; B) full front impact at 56 km/h against rigid barrier - U.S.A. NCAP. Contributors: TI) lower frame; PS) upper rail; PP) main front rail; CB) crash box; TA) front cross member Page 33 of 75

34 The following criteria can be adopted to increase front frame energy absorption capacity: avoid section throats, that could become plastic hinges increase sections and thickness towards the compartment in order to have a progressive reaction of members avoid curves and joints with respect to the longitudinal axis, because these areas would collapse suddenly, effectively wasting the potential contribution of straight members connect single members assigned to the task of energy absorption in order to provide a consistent reaction against different impact counterpart frames and impact directions connect front members to strong cabin frame members instead of single walls, even if they are ribbed or deeply stamped; indeed high impact loads could generate deep crushes of these walls, without providing relevant levels of energy absorption. Figure 4.4: Effect of minor front frame changes on energy absorption: 1) load F crush d recorded in pendulum test for original frame; 2) after black marked changes in frame figure Page 34 of 75

35 As an example of the results which can be attained by the application of these criteria, Figure 4.4 shows a direct absorption comparison between two front frames with a common base. Loads related to crush and therefore absorbed energies are measured. The second frame (B) has been obtained from the first one (A), by implementing the following changes: increase of front rail connecting section to firewall and sills, and increase of stiffness of double firewall for a better fitting to sills. The increase in impact energy was about 80%, with only a slight increase in weight. Another typical solution for today s front frames are crash boxes, made up of a small boxed member screwed to the front rail and to bumper cross member. This device has the task of crushing during a front crash between 10 and 15 km/h, absorbing the impact energy without plastic deformation of the front rail. After crash, the crushed member can be removed and changed, providing significant savings in comparison to traditional repair operations which consist in a complete removal of the mechanical sub-systems and restoring of front members. Figure 4.5 shows an example of a crash box fitted to a car (A), designed as single element (B) and preassembled with the bumper cross member (C and D). The design target for crash boxes (15 km/h) was a consequence of the repair cost rating, which is defined by insurance companies. According to statistical criteria 15 km/h is the impact test speed for all vehicles compared in terms of repair cost rating and consequently car manufacturers design target. Overall impact resistance in insurance testing is provided by bumpers, cross member and crash box. The bumpers also can be considered parts of the safety system for the front part of a vehicle. In fact the main bumper tasks include: overall body protection in parking impact (up to a speed of 4 km/h) or according to individual State safety rules energy absorption and controlled transfer of stress to body frame, when impacted at 15 km/h (insurance impact test) friendly contact (or absence of injury) in case of pedestrian s impact. In practice, in the most recent models, the bumper function is not achieved just by the bumper perimeter (as it cannot be distinguished from other body parts) but is developed under the skin, through absorbing, support and load transfer devices, positioned where needed and performing their task through a soft surface in order to reduce the risk of injuries in case of contact with pedestrians. Page 35 of 75

36 Figure 4.5: Example of body installed crash box (A), view and section of absorbing device (B), bumper beam and crash box assembled (C) and deformed after offset impact test (D) The design of bumpers is once more determined by its aesthetic properties, while the protection function in case of impact, originally less important, is now achieved by specific devices hidden under the bumper itself. For pedestrian protection purposes, the local dynamic stiffness should not exceed 150 kn/m and the allowed deflection space behind the bumper should be not less than 100 mm [20]. Figure 4.6 illustrates some front bumper cross-members in aluminium, plastic and steel. The assembly of different bumper parts can use a variety of techniques. In front crash, doors can contribute to cabin integrity. The rearward deformation of front pillar, mainly at belt line level, can be contrasted by inner and outer belt reinforcement, acting as axially stressed columns. Section and end design of such reinforcements must provide stability under axial loads; materials should provide high yield properties. Page 36 of 75

37 In the front part of the vehicle it is possible to include the bonnet also. The most critical test is usually pedestrian head impact, specified by the rating Euro NCAP. The critical design aspect of this test is the primary influence on head mass acceleration of the empty space available under the bonnet in addition to the bonnet stiffness. The empty space is established by the shape of the body and by the position of rigid subsystems in the engine compartment. Figure 4.6: Examples of different materials and technologies for bumper cross member. IP: injection moulded thermoplastic; EA: extruded aluminium; ST: steel If such dimensional layout is available, according to body styling and adequate room in the engine compartment, the main design task becomes the bonnet frame dimensioning. In the last years the tendency, for the inner structure, is to use distributed design with regular repeated geometry as shown in Figure 4.7. For what concerns the material, when the costs allow it, the aluminium sheets should be preferred to deep drawing steel. Otherwise, some active bonnet lifting systems must be adopted, controlled by a sensor system capable of identifying imminent pedestrian contact and operated by sufficiently rapid actuators (in practice, capable of lifting a bonnet in less than 45 ms) [20]. A number of different systems, Page 37 of 75

38 mechanical and pyrotechnic, are currently available (Figure 4.8). In addition to this active system it is possible to have windshield air-bag as shown in Figure 4.9. Figure 4.7: Examples of inner structures for bonnets Figure 4.8: Examples of mechanical (above) and pyrotechnic (below) devices to lift the bonnet in case of pedestrian impact. The operating time is in the range 30 to 45 ms Regarding the front barrier impact, the bonnet should never penetrate the cabin space through breakage of the windshield. For this reason, the usual design falls into two families of solution: one featuring hinges and bonnet rear end clamping, the other central bonnet bending collapse. The first is performed by hooks on the front body frame, capable of clamping the hinges and slots of the bonnet frame. The second is obtained by a local frame weakening (e.g. a smaller local section) in the central region of the bonnet. This weakening has no influence on the bonnet stiffness, but becomes the principal buckling section when the bonnet is compressed during frontal impact. As a Page 38 of 75

39 consequence of collapsing, the bonnet becomes completely bent, rising the mid-section and losing longitudinal stiffness Side parts Figure 4.9: Windshield air-bag Different parts of the body and of the vehicle contribute to the safety during side impacts. They are briefly illustrated in the following Body side The body passenger compartment can usually be conceived to be a box surrounded by six main walls with frame in wall intersections and more precisely a floor, a roof, two side walls, named body sides, a firewall or dash panel, a rear bulkhead (Figure 4.10). The body side is loaded by static and dynamic loads, by distributed dynamic inertia forces and by pulse loads on certain areas in the event of impact. As concerns material selection, since they have to be strong and stiff as well, the main candidates are steel plates with adequate properties or aluminium assemblies (made by different alloys and processes such as stamping, extrusion, rolling or die casting) or in few cases carbon fibre reinforced mouldings. Page 39 of 75

40 Regarding the behaviour of the central pillar during side impacts, it should be borne in mind that homologation and rating tests use moving barriers with a uniform front crushable surface (aluminium honeycomb) and that the vehicle is impacted below the side belt line. Therefore, the central pillar performs as a bow, loaded in its lower part only, just leaning on or partially embedded at its extremities in crushable body parts. Then the pillar design should provide the lowest possible risk of collapsing at the belt line (despite a sharp section and stiffness change) and, more generally, should deliver outstanding stiffness in all sections, to avoid any crush other than at the crushable controlled extremities. In this case, stiffness does not refer simply to elastic behaviour but rather to permanent collapse; this is the reason why ultra-high strength steel is commonly used for box parts and reinforcements. In some cases it is possible to improve the strength of the main joints between pillars, filling the box sections with structural metal or plastic foam or with plastic reinforcements (in Figure 4.11, the solution adopted in the Citroën C4 Picasso). Figure 4.10: Split view of main body side elements Page 40 of 75

41 4.4. Doors Figure 4.11: Thermoplastic structure used in A pillar of Citroën C4 Picasso In side impacts, it is necessary to distinguish between large and narrow surface contacts. In the first case (e.g. against walls or big vehicles) the door contribution is very low, because impact stresses are mainly addressed to the body side frame (pillars and rocker panels), the strength of which is not influenced by the doors. In the second case (e.g. against poles or trees), the door is directly involved in impact energy absorption and resistance to impact loads: therefore its design is relevant. In the first step of crash, the door is pushed against its housing, which is against body side flanges; the door outer panel starts bending. As a critical deformation level is achieved, door panel and border frame start deforming body side flanges as well as hinges and lock fittings, sliding towards the inside of the cabin. As the door starts sliding, it is no longer held by the body opening flange, but only by hinges and the lock. Therefore it deforms as a membrane under traction and its strength rapidly drops. To avoid such behaviour, first the bending strength of the door must be increased and the door border sliding must be avoided by embedding the door in the body side. The first goal is usually achieved by inserting one or more cross members in the space between the inner and outer door panels: depending on the door configuration as well as hinges and locks positions, different beam lay-out are available (Figure 4.12). Depending on their position, these beams can also contribute to the second goal: for instance, a side bar close to the sill can enable Page 41 of 75

42 the door to avoid sill overriding. If door bars are not sufficient, other devices (e.g. metal hooks or pins in body side frame) must be added. Safety door beams can be manufactured using a range of process (e.g. drawing, extrusion, pultrusion, rolling), with different materials (steel, aluminium, composites) and various shapes (Figure 4.13). The material selected should have high yield and break strength; moreover, bar ends, fitted between outer panel and door frame, must provide enough contact surfaces to meet the body side during crash. Figure 4.12: Examples of door safety beams positioning in the space between outer and inner panel Page 42 of 75

43 Figure 4.13: Examples of boxed and open sections used in door safety beams; detail of link between a tubular beam and door pillar reinforcement. B: tubular beam; S: bracket; O: door inner panel; R: door pillar reinforcement; P: outer panel 4.5. Underrun protections The state-of-the-art design of heavy goods vehicles uses a latter frame concept with two main longitudinal beams (Figure 4.14). These beams are the main load paths, where protective devices can have their interface. Complex and heavy add-on parts have to be designed to close the critical gaps where cars can underrun the heavy vehicle. For the integration of an (all-around) underrun protection for cars and vulnerable road users a complete and comprehensive redesign of the truck/trailer frame is required. Such a new frame concept has to provide the main structure around the vehicle instead of the middle of the vehicle: a space frame concept. This structure has to be designed to provide the operational stability as well as underrun protection with no extra weight compared to the two beam concepts. Page 43 of 75

44 4.6. Cockpit Figure 4.14: Typical underrun side protection used for heavy goods vehicles The cockpit is composed by a series of components that are involved in different ways in the passive safety of a vehicle Restraint systems Restraint systems are the devices inside a cockpit that can mitigate the consequences of a collision, and represent the most important aspect for ensuring the achievement of the safety objective imposed by the legislator or required by rating Safety Belts Seat belts are the restraint systems that are responsible for keeping the vehicle occupants in the right position, so that the occupants avoid sustaining injuries beyond the expected limits due to impact against passenger compartment components during rapid deceleration following a crash. This function must be carried out without penalizing the comfort and freedom of movements, which are necessary for handling the car. Page 44 of 75

45 The R point it is the reference for the definition of seat belt anchorages, for the front and rear seats. Effective anchorages are the points positioned on their respective components, in particular: pillar loop, anchor bracket, slide bar, buckle, tongue and retractor in which the belt changes direction during use, or rather the points at which the webbing should be fixed to assume the same configuration when the belt is fastened. These items must be reported to the occupants of both front and rear seats. For the front seats, for example, the S points identify the effective upper anchor points, and the L points the effective lower anchor points. The correct definition of anchor points, and the relative angles, enables the correct belt routing to be defined in order to obtain the most effective restraint without creating negative effects (for example secondary lesions) with maximum comfort. Since the occupants of the car sit on the seats, it is clear that, if the attachment points of the seat belt are on the seats and have the same possibilities for movement, the belt routing is certainly better in comparison to the case in which the attachment points are positioned totally or partially on the body of the car. For this reason nowadays the anchor of the buckle, which determines the L2 point (Figure 4.15), is located on the seat whereas in the past it was located on the floor of the car. Today the anchor bracket, which determines the L1 point (Figure 4.15) and that used to be placed on the side frame, is often placed on the seat (clearly only in four-door cars). Finally the adoption of the seats with all the three anchor points of the seat belts on the seats (all belt to seat), is possible by moving the retractor from the central pillar on to the seat itself, completes the optimization of the belt routing and comfort. Currently, however, the all belt to seat solution is used only in limited and specific applications. The webbing used for safety belts is designed to resist loads in the order of kn. The webbing is wrapped by the retractor that can be considered the heart of the safety belt system. It is a critical component in terms of occupant safety, it must satisfy some requirements: Locking: o Up to 0.3 G no lock (it must never get blocked up) o Over 0.45 G must lock (it must always get blocked up) Tensile strength > 14.7 kn Length of the webbing m Main types of seat belt used in automotive industries are: Page 45 of 75

46 Lap: adjustable strap that goes over the waist, as shown in Figure It is used frequently in older cars, now uncommon except in some rear middle seats. Passenger aircraft seats also use lap seat belts to prevent injuries Sash: adjustable strap that goes over the shoulder. Used mainly in the 1960s, but of limited benefit because it is very easy to slip out of in a collision Automatic seat belts: some vehicles have shoulder belts that automatically move forward to secure the passenger when the vehicle is started. A separate lap belt is usually included, and the lap belt must be fastened manually. Automatic seat belts have fallen out of favour recently, since the air-bag became mandatory in many countries Three-point: similar to the lap and shoulder, but one single continuous length of webbing. Both three-point and lap-and-sash belts help spread out the energy of the moving body in a collision over the chest, pelvis, and shoulders. The three point belt is the standard seat belt for road cars Belt-in-Seat (BIS): the BIS is a three-point where the shoulder belt attachment is to the backrest, not to the b pillar. The first car using this system in the United States was the 1990 Mercedes- Benz SL. Some cars like the Renault Vel Satis use this system for the front seats. This position allows the shoulder belt to better wrap around the occupant's body, thereby increasing the efficiency of the belt system. In roll-over accidents, it also contributes to keeping the distance between the head and the roof. Moreover, the BIS system is very convenient in the case of removable seats or flexible arrangements. Five-point harnesses: safer but more restrictive than most other seat belt types. They are typically found in child safety seats and in racing cars. The lap portion is connected to a belt between the legs and there are two shoulder belts, making a total of five points of attachment to the seat (strictly speaking, harnesses are never to be fastened to the seat they should be fastened to the frame/sub-frame of the automobile because in racing cars loads are higher and seats are lighter). Six-point harnesses: similar to a five-point harness but includes an extra belt between the legs, which is seen by some to be a weaker point than the other parts. These belts are used mainly in racing Page 46 of 75

47 Figure 4.15: Anchorage seatbelt points on the left, then different types of seat belt To improve the efficiency of seat belt retention, pretensioners have been introduced. These are normally used by the occupants of the front seats and to a lesser extent by occupants of rear seats. Pretensioners can be installed on the safety belts system, on the buckle assembly or on the retractor. The choice depends mainly on the seat configuration. Recently manufactures, especially of higher segment cars or when the target is excellent evaluation in terms of passive safety, have begun to adopt two pretensioners, one for the retractor and one on the anchor bracket. The double pretensioner enables also the sequencing of the two pretensioners according to the type of impact and position of the seat occupant. It also enables a modulation of forces applied to the occupant. Pretensioners can be classified depending on the system of generation of the force, mechanical or pyrotechnic, and depending on the sensors that activate the pretensioners, mechanical or electronic. Today pretensioners are practically all pyrotechnic actuated by electronic sensors. The active control retractor system (ACR) is a system in which the pretensioning can be considered a part of an active safety system, representing an evolution of the pretensioner that comes into action only in the case of a specific event. The ACR restrain adequately the car occupants in case of different dynamic driving situations, increasing the drawing of the seat belts. When a non-usual condition is registered on the vehicle such as sport driving or emergency manoeuvres, the ACR system reduces the slack pretensioning in a reversible mode without activating the pretensioner when a collision does not occur. The ACR system comprises an electric motor connected to the spool of the retractor that allows the drawing of the seat belts to be increased when necessary, then returning to the original conditions when activation is completed [20] Air-Bag The air-bag is an additional restraint system. The air-bag has the function of interacting with the occupants and dissipates the kinetic energy together with the safety belts [20]. The air-bag can be divided into the following categories (Figure 4.16): Page 47 of 75

48 Air-bag for protection against front impact, which can be further subdivided into: o driver air-bag (55-60 litres) o passenger air-bag ( litres) o knee air-bag (12-16 litres) Air-bag for protection against side impact (called also Side-Bag), which can be further subdivided into: o thoracic side-bag (12-18 litres) o pelvic or pelvic/thoracic side-bag (12-18 litres) o head side-bag (15-35 litres) Air-Bag for the protection against rollover (more than 40 litres) Considering the way in which the gas used to fill the bag is generated, today it is possible to have two different types of air-bag, the pyrotechnic one and the hybrid one Dashboard and interior trims Figure 4.16: Different types of air-bag on vehicles The dashboard and the interior trims do not have a specific function from the safety point of view but they contribute to the overall passive safety of the vehicle. Page 48 of 75

49 For what concerns the dashboard it has to contain the air-bag modules for driver, passenger and knee bags. For this reason also the dashboard is a part of the safety system and it needs to be traceable. On the dashboard and other interior trims likes cover for the pillars, head impact experimental tests are done. The acceleration on the head has to be lower than a certain value and the absence of failures of the structure and sharp edges in the impact zone is required to pass the test. For this reason particular attention is put in the choice of material for these components. Usually dashboard and interior trims are made of polypropylene which is charged with mineral and rubber material to improve the stiffness and to avoid brittle fracture. Speaking about the door panel, this component is involved in the safety in case of side impacts. Also in this case it is important the choice of material during the design phase, in order to avoid brittle fracture and the creation of sharp edges in impact zone. Moreover, in some cases different types of energy absorbing materials, likes foam, are put between the door panel and the door structure to further improve the energy absorption in case of side impact Seats The seats also have an important function in term of passive safety of a vehicle. They have to contain and to restrain, together with the safety belt, the occupant in the correct position during an impact event. The final aim is to reduce the injuries to the occupant. For this reason in particular the structure of the seats (Figure 4.17) must be designed considering the load due to impact event. The most critical area are the fastening points of the seat to the floor, because all the reaction forces are concentrated to these points and also the tilting adjustment mechanism of the backrest, that is the hinge between the cushion and the backrest of the seats. On the backrest there are high loads due to inertia forces applied by the chest of occupant. Finally also the geometry of the front part of the cushion is quite important because it contributes to avoid the submarining phenomenon, which occurs when the occupant slips forward and under the lap part of the safety belt. Consequently the biomechanics parameter relative to legs, thorax and in some cases, also head is affected. Page 49 of 75

50 4.12. Rear part Figure 4.17: Structure of a seat made joining different stamped parts The rear frame is conceptually divided in two sub-assemblies. The lower, comprises two longitudinal rails, close to rear wheel houses, connected at both ends by cross-members and supporting the rear floor as main task, together with rear crash handling. Instead the upper sub-assembly layout and tasks depends on the vehicle type, however it does not contribute to absorb energy in case or rear impact. The main task of the rear frame is not only to contribute to torsion stiffness, but also resist rear crash, avoid central floor crushing and finally provide resistance to liftgate loads. The back panel, often boxed, connects the rear rails at their rear end and supports the rear bumper absorbing devices, often made from expanded foam, without a bumper cross member. Similar considerations made for the front bumper can be made also in this section; however, in this case there are not the problems tied to the pedestrian impact. Page 50 of 75

51 5. Proposal for Implementation of Safety features on ELTV Vehicle safety systems are designed to protect occupants during accidents. They can be classified as passive systems and active safety systems. The passive safety systems protect drivers and passengers from injury once a collision occurs. Passive safety system includes primary systems and secondary systems. Primary systems are ready to use in any accident. They include bumper bars, body panels, seatbelts (safety belt), crumple zones and collapsible steering columns (Figure 5.1). A secondary system has to be activated to work and is only necessary in severe accidents. The two most popular types of secondary systems are supplemental restraint system air-bag, and seatbelt pre-tensioners. On the other hand, active safety systems help the drivers to avoid accidents. These systems function behind the scenes, monitoring the driving conditions and actively adjusting the driving dynamics of the vehicle to minimize the risk of an accident. Active systems provide a degree of protection for occupants unavailable in passive systems and they reduce the likelihood of a situation that would require the use of passive systems. Figure 5.1: Safety features in automobile [21] The goal of the OPTIBODY project is to develop new concept of modular structural architecture for electric light trucks or vans (ELTVs) focusing on the improvement of passive safety system. The detailed study of the safety features is divided into four parts: Page 51 of 75

52 Crumpling zone (front part) Side part Cockpit Rear part 5.1. Conceptual design of crumpling zone (front part) The crumple zone is a structural feature used in vehicles, mainly in passenger cars. They are designed to absorb the energy from the impact during an accident by controlled deformation of the structure. An early example of the crumple zone concept was used by the Mercedes-Benz engineer Béla Barényi on the mid 1950s Mercedes-Benz "Ponton". This innovation was first patented by Mercedes-Benz in the early 1950s. He divided the car body into three sections: the rigid nondeforming passenger compartment and the crumple zones in the front and the rear part. They are designed to absorb the energy of an impact (kinetic energy) by deformation during collision. Typically, crumple zones are located in the front part of the vehicle, in order to absorb the impact of a head-on collision, though they may be found on other parts of the vehicle as well. Some racing cars use aluminium or composite/carbon fibre honeycomb to form an impact attenuator that dissipates crash energy using a much smaller volume and lower weight than road car crumple zones (Figure. 5.2). Figure 5.2: Crumpling zone Modular design approach is suggested to improve the production process and the after sale service, besides helping to achieve low maintenance cost and minimum part replacement. The crumple zone Page 52 of 75

53 has been introduced in the proposed vehicle model to improve the safety level allowing a controlled deformation for the frontal section of the vehicle (Figure 5.3). Figure 5.3: Crumpling zone of proposed electric truck Crumple zones are deliberate weak spots that vehicle designers have placed in the structure of a car. While this might appear contrary to passenger safety, but placing the weak spots in strategic locations, it is possible to collapse the structure in a controlled manner. This creates 2 mechanisms by which the energy from an impact can be managed: 1. Deforming the metal structure of the car, the energy from the impact is converted into heat and mechanical deformations. This reduces the amount of energy left to damage the passenger area. 2. Since the collapse is controlled, energy from the impact can be directed away from the passenger area. In most designs, force from the impact is channelled to areas such as the floor, bulkhead, sills, roof and bonnet. As shown in Figure 5.4, the impact load is intended to be directed from crumpling zone to the chassis, roof, and floor. Page 53 of 75

54 5.2. Force on the passenger Figure 5.4: Load transfer due to front impact crash The crumple zone, the seat belts, the air-bag, and padded interiors have to be designed to work together as a safety system to reduce the force and the acceleration of the impact on the passenger body (Figure 5.5). In a collision, slowing down the deceleration of the human body reduces also the force involved. Crumple zone Seat belt Airbags Padded interior Figure 5.5: Sequence of energy dissipation For this reason, it is necessary to have in the front part of the vehicle, deformable structures able to manage a progressive deformation and consequently absorption of energy. In this way it is possible to reduce the force applied to the vehicle occupants. For this reason, special attention has been given to the material types, geometry profiles of the crumpling zone, and position of add-ons to improve the energy absorption capability Recommended materials used for crumple zone Crumple zones are constructed in many different ways in order to obtain a higher safety rating. The most used solution are made with steel or titanium, high density and low density polymeric foam, spaced reinforcing fibres, spaced mechanical ribs and reinforced metal inserts with notched section Page 54 of 75

55 for predetermined crumpling. In this project the crumpling zone could consists of number of parts to achieve controlled deformation to reaction force due to impact against barrier in frontal crash. As shown in Figure 5.6, the crumple zone will firstly have high density polymeric foam placed in front of the cabin. Secondly reinforced fibres spaced between the high density polymeric foam and the low density foam. This low density foam has greater absorbing ability than the high density one. It is positioned in a more advanced position than the high density foam. Thirdly the foam is caged in mechanical ribs made from either steel or titanium and have been specifically designed to crush downwards under the car. Lastly the front end of a car can be built with steel or titanium. These metal pieces are reinforced with notched metal inserts which will cause the metal to either crush upwards, downwards or to the side depending on the collision. In this way the engine is safe for movement and consequently the cabin and occupants are safer Side part Figure 5.6: Material used for crumpling zone Different parts of vehicle body contribute their own parts to enhance the safety level during side impacts. In this deliverable report brief proposed solutions are illustrated from point of view of passive vehicle safety Passenger compartment Also for the ELTV vehicles, the passenger compartment should be a stiff cage which protects the occupants. At the same time it is necessary to keep low the weight of the vehicle. One important difference from the cockpit of common cars is that the R point of this type of vehicle and Page 55 of 75

56 consequently the floor is quite high. For these reasons it is suggested to design this part of the vehicle like a cage made with extruded profiles in light metals (aluminium for example). The stiffest point should be the lower front and rear joint, which are subjected to high load due to front and side impact. For these reasons the longitudinal beam under the floor and the joint between vertical rear pillar and the longitudinal beam has to be designed with attention. For the joining of different profiles, it is possible to use different solutions: welding, mechanical fastening (bolts, rivets) and also adhesive bonding. The panels which close the surface of the passenger compartment do not carry significant structural contribution. The roof is only a closing panel, which can be designed considering only the distributed load of snow. The doors also do not have significant structural importance as it will be discussed in the following section. The firewall divides the cockpit from the engine compartment, but few loads are applied on this part. At the end the rear wall should divide the luggage area from the cockpit. Due to these considerations, all these panels can be made with plastic or plastic reinforced materials. The solutions described are oriented to obtain safety structure limiting the weights of the structure The Door Usually, in the design of common cars, the door has an important behaviour in side impact crash, in particular when the impact against a concentrated obstacle (pole) is considered. However, for what concerns the ELTV vehicles, the contribution of the door is not very significant. This is due to the position of the door that is higher than in common car. In turn, the position of the door is due to the higher position of the R point of the occupant, which is common for this type of vehicles. Also on the base of consideration in the previous section, this type of vehicle can have a very simple door without particular structural behaviour, but above all, the main contribution is the insulation. Due to the type of vehicle, also the devices usually assembled on the door are reduced to those necessary. In this way it is possible to obtain also a very light door structure. Also for this component it is possible to consider a structure made with extruded profile and cover panels in plastic or composite. In the door for the common car also a side impact beam is present. For the ELTV vehicles this component is not necessary, because in case of impact, due to the position of R point, the central part of the door does not work while the lower part of the cabin structure is more involved. Page 56 of 75

57 5.7. The underrun and side crash protections In Europe, the ECE regulation 73 requires that all trucks and trailers have open underrun protection. The EC Directive 89/297/EEG prescribes open underrun protection. In the OPTIBODY project the Directive 89/297/EEG is taken as initial input reference to develop a new concept. For the ELTV vehicles the underrun protection system can be used also to protect the battery compartment. To obtain those double targets at the same time, the underrun protection system is proposed to be assembled on the cross member of chassis. The underrun protection system then can be considered as side crash protection system. It can be composed by side beam and crash boxes bolted to the main chassis, as shown Figure 5.7. This modular solution improves the maintainability of damaged parts after side impact Cockpit Figure 5.7: Add-on crash beam/boxes (underrun protection system) The cockpit is composed by a series of components such as dashboard, interior trims, restraint systems, seats. They are involved in different ways in the passive safety of a vehicle. During development of a vehicle cockpit, ECE-R 21 regulation is generally considered. This regulation contains uniform provisions concerning the approval vehicles with regard to their interior Page 57 of 75

58 fittings. The scope of this regulation includes: interior parts of the compartment, arrangement of control, roof and sliding roof, seat-back and rear part of the seats Restraint systems For what concerns the restraint system the EU general safety regulation can be adopted. The existing different standards established by different countries and organizations do not have major difference among them. Moreover from this point of view no particular requirements are necessary for this type of vehicle. The seat belts for the ELTV can be conventional three point seat belt according to the Regulation No 14 of the UNECE, as shown in Figure 5.8. The belt pretensioner is included in the safety belt system. For what concerns the air-bag, the proposal for the ELTV vehicles is the following: Driver air-bag: due to the presence of the add-on system this air-bag can be less aggressive than the common driver air-bag. Also the case structure of the air-bag, can be designed to reduce its weight Side air-bag: in this case it is possible to think to a specific innovative air-bag not fixed on the side vertical arm of the seat structure, but fixed on the lower part of the cabin structure, which is the part more involved in a side impact Roll over air-bag: this can be considered additional air-bag, fixed in the upper part of the cabin. Its development can be based on the products already developed for SUV vehicle. These airbag use a specific fabric with higher thickness and permeability which allow to the bag to stay inflated for longer time than common air-bag Page 58 of 75

59 Figure 5.8: Seat belt configuration Rear Part Careful design approaches on rear parts of vehicle improve the safety level of passengers against rear impact crash. Similar to front crumpling zone, in recent vehicles energy absorbers, such real transverse beam and crash boxes, are introduced to reduce the reaction load that might be transferred to the occupants. Besides, this horizontal beam reduces the injury on the occupants and damage of the vehicles that might be occurred due compatibility problem. In the ELTV, a horizontal beam, made of lightweight material can be joined together with crash boxes and assembled to the rear part of chassis with mechanical fastener. In this way the reparability is improved. Always considering the rear impact, for this type of vehicle is suggested to introduce specific system inside the cockpit, oriented to reduce the injury to the neck in case of rear impact, the so called whiplash phenomenon [9]. Different types of systems exist to avoid this problem, some of them are more simple because are mechanical mechanism based on the movement of the occupant s body, other are more sophisticated and based on sensors and signal [20]. For the type of vehicle considered, is suggested to introduce the mechanical devices in order to reduce the costs, but at the same time, being the vehicle for urban area, this type of devices can results very useful to improve the safety, being this type of injuries, very frequent in urban contest. Page 59 of 75

60 6. References [1] European Commission, Mobility & Transport (Directive 2002/24/EC): Directive 2002/24/EC of the European Parliament and of the Council of 18 March 2002 relating to the type-approval of two or three-wheel motor vehicles and repealing Council Directive 92/61/EEC. [2] European Commission, Mobility & Transport (Directive 2004/86/EC): Council Directive 93/93/EEC on the Masses and Dimensions of Two- or Three-Wheel Motor Vehicles. Adaption to technical progress: Commission Directive 2004/86/EC. [3] European Commission, Mobility & Transport (Directive 97/24/EC): Directive 97/24/EC of the European Parliament and of the Council of 17 June 1997 on certain components and characteristics of two or three-wheel motor vehicles. [4] Vehicle crashworthiness and occupant protection by, Paul Du Bois, Clifford C. Chou, Bahig B. Fileta, Tawfik B. Khalil,Albert I. King, Hikmat F. Mahmood Harold J. Mertz,Jac Wismans, 2004 [5] EUROPEAN NEW CAR ASSESSMENT PROGRAMME (Euro NCAP) FRONTAL IMPACT TESTING PROTOCOL, Version 5.2, November 2011 [6] EUROPEAN NEW CAR ASSESSMENT PROGRAMME (Euro NCAP), SIDE IMPACT, TESTING PROTOCOL, Version 5.2, November 2011 [7] EUROPEAN NEW CAR ASSESSMENT PROGRAMME (Euro NCAP) ASSESSMENT PROTOCOL OVERALL RATING, Version 6.0, July 2012 [8] EUROPEAN NEW CAR ASSESSMENT PROGRAMME (Euro NCAP) POLE SIDE IMPACT TESTING PROTOCOL, Version 5.2, November 2011 [9] EUROPEAN NEW CAR ASSESSMENT PROGRAMME (Euro NCAP), THE DYNAMIC ASSESSMENT OF CAR SEATS FOR NECK INJURY PROTECTION TESTING PROTOCOL, Version 3.1, June 2011 [10] EUROPEAN NEW CAR ASSESSMENT PROGRAMME (Euro NCAP), PEDESTRIAN TESTING PROTOCOL, Version 6.1, July 2012 Page 60 of 75

61 [11] EUROPEAN NEW CAR ASSESSMENT PROGRAMME (Euro NCAP) ASSESSMENT PROTOCOL CHILD OCCUPANT PROTECTION, Version 6.1, July 2012 [12] EUROPEAN NEW CAR ASSESSMENT PROGRAMME (Euro NCAP) ASSESSMENT PROTOCOL SAFETY ASSIST, Version 5.6, July 2012 [13] Department of Transport and Region, Australian Design Rule, 19 September 2007 [14] Safety Companion, CARHS, 2012 [15] China Automotive Technology and Research Center, C-NCAP Management Regulation, 2009 [16] D. Egertz, S. Kazemahvazi, S. Hallström, Vehiconomics ABNovel Safety Requirements and Crash Test Standards for Light-Weight Urban Vehicles, Stockholm January 2011 [17] A. Otte, Whiplash Injury: New Approaches of Functional Neuroimaging, Springer, Berlin, 2012 [18] APROSYS Deliverable D7.4.2B Complete demonstrators in various numerical codes along with procedural report for virtual testing implementation in pedestrian impacts 2009 [19] Private communication with Prof. Dominique Césari 2012 [20] L. Morello, L. Rosti Rossini, G. Pia, A. Tonoli, The Automotive Body, Springer, 2011 [21] A. Robinson, W.A. Livesey. The Repair of Vehicle Bodies P th Edition. Butterworth- Heinemann Page 61 of 75

62 7. Appendix - Analysis of current vehicles behaviour in whiplash Since there are various possibilities regarding the OPTIBODY structure, as a starting point with regard to the requirements that it should fulfil, related to rear protection, the behaviour for the OPTIBODY structure should improve, at least, the structures of current vehicles. The fact that the vehicle within the project has been decided as a L7e category vehicle, with a maximum weight of 450 kg (550, means that in the case of being struck by any other vehicle, will increase the probability of injury to the occupants due to the differences in weight. Therefore, from a structural point of view we believe that efforts should be made in the design, so that its behaviour under rear impact is, at least, at the same level of vehicles currently on the market. To characterize the behaviour of vehicles on the market, a first deep analysis of a wide database (from AGU), containing a total of 157 rear collisions crash tests at low speed has been made. After this analysis, the study Acceleration pulses and crash severity in low velocity rear impacts real world data and barrier tests, containing rear collisions crash test has also been analyzed Analysis of AGU database The database contains a total of 157 rear-end collision tests at low speed, allowing a good characterization of the current vehicle behaviour under a rear impact. Collision speeds contained in the database ranging from 15 km/h to 28 km/h are quite low speeds but considered sufficient to produce whiplash injuries on the struck vehicle occupants. As the main parameters which characterize the performance of the vehicle structure and the possibility of injury to the occupants, associated with whiplash are speed variation and average acceleration suffered by the struck vehicle, these are the main parameters analysed. As is scheduled the testing of the OPTIBODY concept under the RCAR criteria of reparability, rear impact at a speed of 15 km/h, will extract data for those impacts where the striking vehicle speed is above 15 km/h. Page 62 of 75

63 The following graphs show the values of mean acceleration and variation of speed experienced by the struck vehicle, depending on the speed of the striking vehicle Delta V (km/h) Stricking vehicle speed Figure 7.1: Values of variation of speed experienced by the struck vehicle, depending on the speed of the striking vehicle 6 5 Mean acceleration (g) Stricking vehicle speed Figure 7.2: values of mean acceleration experienced by the struck vehicle, depending on the speed of the striking vehicle Page 63 of 75

64 As shown in the above graphs, for impact speeds between 15 km/h and 28 km/h, the speed variation of the majority of tested vehicle is ranging between 8 and 12 km/h. Most of the mean acceleration values are between 1.5 and 3.5 m/s Study: Acceleration pulses and crash severity in low velocity rear impacts real world data and barrier tests This study analyses the different collision parameters in vehicle tested in rear crash tests against rigid mobile barrier with a weight of 1000 kg and at a speed of 15 km/h (old RCAR rear tests). Page 64 of 75

65 Impact a mean v at T p v measured (G) (km/h) (km/h) LC LC LC LC LC LC LC LC LC LC LC LC LC LC LC LC LC LC OW OW GR GR GR GR GR GR GR GR GR OW GR GR GR Table 7.1: Results from RCAR tests Analysing the data provided, it is noted that regardless of the type of vehicle, most mean accelerations are between 2 and 3.5 m/s 2. The values for speed are in most cases between 6 and 10 km/h. Page 65 of 75

66 3.2. Biomechanical analysis of whiplash injuries Each of the crash tests of the AGU database were grouped into different intervals v (change of velocity experienced by the struck vehicle). We analysed pulses of acceleration experienced by the struck vehicle and for each of the v intervals has been created an acceleration pulse that is entered in the MADYMO software (MAthematical DYnamic MOdel). MADYMO is a software program that reconstructs the dynamic behaviour of physical systems focusing on the analysis of collisions between vehicles and analysing the injuries suffered by the occupants. This program allows to analyse the injuries suffered by the occupants in a collision and to determine its origin. Likewise, it allows analysing the behaviour of restraints systems on the occupants (seat belts, airbags, headrest). With MADYMO the movement experienced by the driver and the occupant of each of the cases analysed within each interval is going to be simulated. For this we have constructed a simplified model of the interior of the vehicle, comprising the floor of the cabin, the driver's seat and right front passenger, the headrest of the seats, the seat belt of the seats, steering column and steering wheel, dashboard and windshield Dummy model For simulation, the BioRID II dummy was used: this dummy was developed due to the need of a more biofidelic dummy in rear-end collisions. This dummy has a spine divided in 24 vertebrae. Furthermore, the spinal column and torso are more flexible than in the case of the Hybrid III dummy. Page 66 of 75

67 Figure 7.3: BioRID II dummy models 7.2. Validation This dummy model has been validated conducting tests from different components. The model has been validated by chest calibration test, this test involves placing the spine, jacket and head on a sled through which receives a pulse Model of vehicle cabin The cabin is composed of a windscreen, the A-pillar, steering wheel and steering column, dashboard, the cabin floor, the seat with headrest and seat belt (for both the driver and the right front occupant). Below are some images where the model used can be seen. Page 67 of 75

68 Figure 7.4: BioRID II dummy models in the passenger compartment In the previous image (Figure. 7.4) the BioRID II model of occupant is placed in the passenger compartment of a vehicle (for the driver). Page 68 of 75

69 Figure 7.5: Passenger compartment Page 69 of 75

70 Below are the NIC results obtained for each v intervals obtained from the crash tests database analysed. Also calculated the risk of injury associated to the NIC value, both for driver and right front passenger. Furthermore, the risk is calculated as a function of v and as a function of mean acceleration. v 1 v 3 (km/h) 3 v 5 (km/h) 5 v 7 (km/h) 7 v 9 (km/h) 9 v 11 (km/h) 11 v 13 (km/h) 13 v 15 (km/h) 15 v 19 (km/h) NIC DRIVER NIC PASSENGER a max (G) g a mean (G) Risk (%) According NIC DRIVER According NIC PASSENGER According v According a mean Table 7.2: Results of the simulations Details for every simulation are summarized and shown below. Page 70 of 75

71 Interval v a max a mean 4< v 8 km/h 6 km/h 3,0 g 1,213 g Acceleration(m/s 2 ) Time (s) RESULTS DRIVER OCCUPANT NIC 7,7638 NIC 14,8910 RISK ANALYSIS DRIVER OCCUPANT RISK 2% RISK 16% Page 71 of 75