Base for enforcement WIM systems

Transcription

1 Base for enforcement WIM systems Emil Doupal RTS GmbH, Höhenring, 0 Zürich David Cornu david.cornu@kistler.com Kistler Instrumente AG, Eulachstr. 00 Winterthur Ivan Kriz i.kriz@cmi.cz Czech Institute of Metrology, Czech Republic Abstract The Czech Republic Government decided to release a new regulation in the traffic law no. 0/00 which integrates Weigh in Motion equipment as part of the road enforcement systems, with effect from st January 0. This should enable to use high-speed WIM systems for direct law enforcement. The Czech Metrology Institute (CMI) as the competent local body for stipulating metrological and technical requirements in co-operation with the Transport Research Institute and the company RTS GmbH defined the metrological and technical requirements as well as the methods of certification for high speed weighing equipment. The technical requirements were based on the document OIML R - Automatic instruments for weighing road vehicles in motion and measuring axle loads. The road tests were based on the document pren Weigh in Motion of Road Vehicles, a draft European standard from November 009 prepared by the FiWi (FEHRL Institutes WIM initiative) working group. The paper presents two different WIM systems and the results achieved. Such systems allow the extension of WIM applications from the standard high-speed traffic data collection to the enforcement application. One of the unique procedures embedded in the new WIM systems is the advanced data processing method called validity of measurement, which identifies data out of specification due to unusual vehicle and driving behavior. Keywords: Weigh In Motion, WIM standard, high-speed WIM, direct enforcement Base para fiscalização com uso de sistemas de pesagem em movimento Resumo O Governo da República Tcheca decidiu implantar um novo regulamento na lei de trânsito nº 0/00, que integra o equipamento de pesagem em movimento (Weigh-in-Motion) como parte dos sistemas de fiscalização de estradas a entrar em vigor a partir de º de janeiro de 0. Isso deve permitir o uso de sistemas de PM de alta velocidade para fiscalização direta da lei. Como órgão local competente para estipular requisitos metrológicos e técnicos, o Czech Metrology Institute (IMT), em cooperação com o Transport Research Institute e a empresa RTS GmbH, definiu os requisitos metrológicos e técnicos e também os métodos de certificação para equipamentos de pesagem em alta velocidade. Os requisitos técnicos foram decididos com base no documento OIML R - Automatic instruments for weighing road vehicles in motion and measuring axle loads. Os testes de estrada foram executados com base no documento pren Weigh in Motion of Road Vehicles, uma versão preliminar da norma europeia de novembro de 009, elaborada pelo grupo FiWi (FEHRL Institutes PM Initiative). Este trabalho apresenta dois sistemas diferentes de pesagem em movimento (WIM) e os resultados obtidos. Esses sistemas permitem a extensão de aplicações da WIM desde a coleta padrão de dados de tráfego em alta velocidade até a aplicação da fiscalização. Um dos procedimentos singulares

2 integrados aos novos sistemas de pesagem em movimento é o método de processamento de dados avançado chamado validade de medição, que identifica os dados obtidos correlacionando-os com o comportamento incomum do veículo e da direção. Palavras-chave: Pesagem em movimento, Norma de PM, PM de alta velocidade, Fiscalização direta Introduction The Czech Metrology Institute (CMI), as the competent local body for stipulating metrological and technical requirements for a specified measuring device and for the stipulation of test methods for type approval and for verification of a specified measuring support document issues: Measuring of a general nature - stipulating metrological and technical requirements for specified measuring devices, including test methods for verifying specified measuring devices: "high-speed weigh-in-motion road vehicle scales".articles that are out of formatting will be excluded from the evaluation process. Metrological requirements Metrological requirements are based on the requirements of recommendation OIML R - Automatic instruments for weighing road vehicles in motion and measuring axle loads - Part : Metrological and technical requirements Tests() and pren - Weigh in Motion of road vehicles, Version 00/ (). Service conditions Operating temperature range Scales must meet metrological requirements at temperatures from -0 C to +0 C. Operating speed The operating speed must be indicated and/or printed out only after the entire vehicle has been weighed in motion. The error in the indicated operating speed must not exceed km/h. The speed range for system approval will be defined in accordance to the speed, during the approval test runs. Measurements under or over the approved speed interval can t be used for direct enforcement. Weighing range The manufacturer of the scales specifies the weighing range, which is given by the values Max and Min, and must conform to the values listed in Table. Maximum permissible errors Vehicle mass (Gross Vehicle Weight, GVW) max. permissible errors is ± % Axle load and axle group load max. permissible errors is ± % Units of mass and load measurement used by the equipment are kilogram (kg) or tonne (t). Scale interval must not exceed the values for axle load 0kg and for vehicle mass 0kg.. Technical requirements Scales are an automatic measuring system composed of the following parts: load receptors installed in the roadway, vehicle recognition equipment, equipment for measuring vehicle speed, an indicator, a printer, a recording device, equipment for the optical identification of vehicles, auxiliary equipment, that as a whole is capable of measuring dynamic forces on tires and detecting the presence of a moving vehicle on the load receptor over time, and of calculating total vehicle mass and axle or axle load values, speed, plus other vehicle parameters required by special legislation (e.g. axle separation, vehicle type).

3 Load receptor (sensor) The sensor installed in the road must detect the presence of a moving vehicle and record the dynamic forces on the tires. Vehicle recognition equipment (data logger) Scales are intended for operator-free operation, and thus must have vehicle recognition equipment. This equipment must detect the presence of a vehicle in the weighing zone and must ascertain when the entire vehicle was weighed. The equipment must permit the categorization of vehicles in accordance with special transport legislation (). The scales must not indicate record or print out the mass of the vehicle if all of the vehicle's wheels were not weighed or the vehicle was not recognized. Equipment for measuring vehicle speed The speed of a vehicle during weighing must be indicated, and if appropriate recorded and printed out as part of the vehicle weighing record, in km/h, after being rounded to the nearest whole number. The scales must not indicate record or print out the mass or axle or axle group values for any vehicle that has passed over the load receptor at a speed outside the specified range of operating speeds without an accompanying clear warning signal that these results are not verified. Indication equipment Indication during normal operation Displayed mass and load values must be indicated precisely and unambiguously, and must not lead to errors. Scales are intended for indication of the following values: measured values of total mass, including the unit of measurement, measured values of axle or axle group load, including the unit of measurement, maximum permissible total mass value, including the unit of measurement, maximum permissible axle or axle group load, including the unit of measurement, the speed of the vehicle, the time (the date, hour, minute and second the measurement was performed), if appropriate. If scales in a corresponding application are not intended and approved for total mass or axle or axle group load, the scales can indicate this value for information only, clearly marked that this indication is not in the verified range of measurement. Optical vehicle recognition device Scales must be equipped with a device for the unambiguous recognition of those vehicles that during weighing were found to exceed specified mass parameters. This recognition must meet security, integrity and authenticity requirements. Imaging unit Scales may be equipped with a camera that captures the weighing situation with safe identification of the weighed vehicle, which is displayed on a connected remote display along with the following values measured by the scales: Measured values of total mass, including the unit of measurement, Three measured values of axle or axle group load, including the unit of measurement, optionally also: maximum permissible total mass value, including the unit of measurement, maximum permissible axle or axle group load, including the unit of measurement. Image recording unit Scales may be equipped with an image recording unit that must capture the situation during weighing, ensuring identification of the vehicle being weighed. An image-recording unit working in automatic mode should enable the setting of a limit mass for image recording. The situation on the scales is recorded by a digital camera, which outputs individual digital images or video sequences stored in digital memory. The integrity and authenticity of video sequences that are to be archived must be ensured to prevent undue changes to the content of images and measured data, or improper assignation.

4 Resistance to external influences Physical robustness, Weather resistance, Dust and water resistance, Electromagnetic compatibility Power Scales powered from the electrical grid must meet metrological requirements under normal voltage fluctuation conditions. Measuring device security and fraud prevention Scales must not have characteristics that would facilitate fraudulent use, and there must be a minimum of ways in which they can be unintentionally improperly used. Components that are not intended to be disassembled or adjusted by the user must be protected from such activity.. Hardware and software security All scale equipment including software, which is intentionally to be prevented from disconnection or removal by a user or other individual, must be equipped with a housing or other suitable security means. It must be possible to seal housings after their closure; sealing points must be easy to access in all instances. All parts of the measuring system that cannot be protected by housings must be equipped with sufficiently effective means of preventing operations that tend to influence measuring accuracy. Each piece of scale equipment that could influence measuring results, especially equipment for calibration and adjustment of scales or for correction of measured values, must be sealed.. Installation Roadway geometry and road characteristics according to pren () Measuring device type approval External inspection, tests of the scales' resistance to disruptive environmental effects, functional weigh-in-motion tests on location during road traffic. Simulated functional tests in the laboratory The metrological body approving measuring device types can accept a manufacturer's proposal to modify the method and manner in which simulated functional tests are performed, if suitable with regards to the specifics of the technology and design of the scales' measurement chain. Tests of resistance to the influence of the external environment, Tests of resistance to physical effects, Tests of resistance to random vibrations, Shock resistance test, Weather resistance tests, Resistance to limit temperatures, Resistance to operating temperatures, Resistance to air humidity, Dust and water resistance, Electromagnetic compatibility (EMC) tests, Resistance to interference caused by power lines, induced by high-frequency fields, Resistance to radiated high-frequency electromagnetic fields at radio frequencies, Resistance to electrostatic discharge, Resistance to electrical fast transients/bursts, Resistance to electrical surges, Resistance to power-frequency magnetic fields, Resistance to AC mains voltage dips, Limit power voltages test During this test the scales must function normally, and the error during a simulated functional test must not exceed the maximum permissible error listed in.. Weigh-in-motion accuracy road tests Complete scales installed at a weighing location agreed upon with the client are subjected to weigh-inmotion accuracy tests.. Test equipment Reference vehicles Reference vehicles shall be selected for weigh-in-motion tests so that they represent various axle configurations, truck/trailer configurations, truck/trailer connection systems and suspension systems (according to pren ())

5 Reference vehicle loading During testing, reference vehicles must be used both unloaded, and loaded in a way that two significantly different load levels are used (according to pren ()). Reference scales During testing, standalone reference scales must be available to determine the conventional true mass value of each vehicle and the reference single-axle or axle group load. Reference scales for measuring reference axle load and vehicle mass of a reference vehicle To determine the conventional overall mass value of reference vehicles, preference is given to standalone reference scales that can determine the conventional mass value of each reference vehicle by weighing it all at once with an error less than or equal to one third of the applicable MPE for weigh-inmotion. To determine the conventional axle load, stand-alone portable reference scales for weighing Class III or IV vehicles are used, or for low-speed scales of accuracy class or better. Tests are performed under operating conditions stipulated by the manufacturer of the scales in question. Table Weighing range Weighing range Min [kg] Max [kg] Axle load 000 0,000 Vehicle mass 00,000 or as specified by special legislation. Determining reference values for GVW and axle loads of reference vehicles Conventional true value of the reference vehicle mass Reference scales are used to determine the GVW and axle load values for an unloaded and loaded reference vehicle. The reference scales are used to sequentially determine the load on each axle of the reference vehicle, with at least three to five test runs in both directions. The mean reference axle load is calculated as the arithmetic average of recorded values. To correct for the influence of the method used, the total vehicle mass is calculated by axles as the sum of mean load values on individual axles VM. The corrected mean reference load value per axle is then: VM ref CorrAxlei = Axlei () VM VM ref is the conventional value of each reference vehicle mass determined by full-draught weighing To verify that reference axle loads are correct, the following must apply: VM ref = CorrAxle i i The corrected mean load value (see above) is used as the conventional per-axle load of the reference vehicle. Verification of scales installation at the weighing location Road geometry is checked, and must meet all criteria according to pr EN.. Weigh-in-motion reference vehicle tests Test runs Each reference vehicle, unloaded and then loaded, must perform at least five test runs at each of the three following speeds: near the maximum operating speed, v max, near the minimum operating speed, v min, near the middle of the operating speed range, (each reference vehicle must thus perform a total of 0 test runs). For every five test runs at a given tests speed, the vehicle must be positioned above the

6 centre of the load receptor three times, once on the left and once on the right side of the load receptor. Test run speed Vehicle speed must be kept as constant as possible during each test run. Scales must indicate and record the speed of the tested vehicle as it passes over the load receptors. Weigh-in-motion accuracy tests The values of all vehicle mass indications and all axle load indications are recorded. For each recorded value (total vehicle mass, axle or axle group load), the relative error d is calculated in percent: C R d = 00 () R C is the value measured by the scales, R is the corresponding reference value measured by the reference scales. The number of relative errors d that exceed the stipulated maximum permissible error according to. for each quantity is determined, and this number is expressed as the relative number of values for each quantity as follows: n P de = 00 () N n is the number of calculated differences exceeding the maximum permissible error, N is the total number of recorded values for the given quantity. The number of relative errors exceeding the maximum permissible error P de must not be greater than %, with their distribution among individual vehicle types being recorded. Operating speed blocking test During the operating speed blocking test, a test run by one reference vehicle must take place at a speed outside the operating speed range, as follows: a) at a speed at least % higher than the maximum operating speed, v max, b) at a speed at least % lower than the minimum operating speed, v min, (if the scales can be used for this). The scales must detect the above conditions and must react. Operating speed test To determine and test operating speed during a weigh-in-motion test, six test runs shall take place with an unloaded two-axle rigid reference vehicle across load receptors at a constant speed. Three runs must take place near the maximum operating speed v max, and three additional runs must take place at exactly the listed minimum operating speed v min. The indicated operating speed error must not exceed the error given in pren (). Vehicle recognition device blocking test Two reference vehicles are connected by a suitable towing device that ensures constant distance in order to create an atypical sequence of trailers between the rear axle of the pulling vehicle and the front axle of the pulled vehicle. The scales must then: recognize the combined vehicle as two vehicles, determine the correct axle group load or detect an error, detect the fact that all weighed wheels of the vehicle were not weighed during the weighing operation, and not indicate or print any mass or load values if the indication and/or printout have a clear warning. The Initial verification test, Subsequent verification test, Visual inspection, Functional weigh-in-motion tests in road traffic must be provide in accordance with the pren ().

7 Practical application of the CMI document. Validity of Measurement Based on daily experiences, drivers of heavy overloaded trucks are often trying to confuse road sensors. They use several tricks, such as accelerating, sudden breaking or any other maneuvers just to make WIM sensors unable to measure their current weight precisely. Validity of Measurement is a unique procedure embedded in new WIM products to identify such driver s behavior. And more than that, to project such information into measurement results back and thus make them much more accurate. Using the Validity of Measurement concept, WIM system is ready for full integration into automatic weighing system.. Core Functionality From the user s point of view, Validity of Measurement is one number in percentage indicating the success of measurement. In addition, this validity number is also followed by full list of factors having some exact influence during measurement process. End users can then easily interpret what has happened in system. Figure Vehicle detail with 9% validity of measurement Maneuver Detection Based on speed and weight data from each wheel and axle, and compared to time, WIM system is able to detect following vehicle maneuvers: Acceleration/Speed Up. Even minor changes in each wheel speed can be detected. De-acceleration/Brake Actuating. In opposition on acceleration, even minor changes in each wheel speed can be detected. Slight turning left or right. If vehicle wheels have different speed on each axles and vehicle trail is turning aside, system will identify this. Sharp turning left or right. If vehicle is turning rapidly, system is able to recognize and identify that. Lane Pass Because of all of vehicle s events are stored in database (such as data from WIM sensors, data from loop detectors and other events), vehicles driving from one lane to another can be recognized and weighed properly. If some wheel information is missing in one lane, system will try to find out relevant information in connected lanes and pair all this information into one vehicle record. As result of Lane Pass detection, validity trace will include all necessary information for identifying incorrect vehicle drive.

8 Vehicle Signature For WIM system, each vehicle has a unique signature. Signature is footprint of the vehicle mass moving over inductive loops. In classification model, each signature is then compared to special dictionary. Classification results can also have direct influence on validity value itself. Figure Lane pass Figure Vehicle signutare Approval results Based on the CMI document () the type approval of two Cross s.r.o (CZ) and Camea s.r.o (CZ) WIM systems during September and November 00 has been organised. Below are present the results of the WIM system accuracy ( different system configuration) calculated by pren method. According to those results and with aspect to fulfilling of all other metrological test the system received the type approval for direct enforcement based on WIM measurements under application of measuring validity processing method. Three measurements during approval test were out of permissible error, because the wheel positions of the test vehicle were out of sensors installed in road. Therefore the three measurements were repeated.

9 The WIM system Camea was installed into a special pavement type Zenit (drain asphalt filled with cement milk / elastomeric mixture) and additional machined grinded by a special procedure. The following layout shows the system configuration inclusive application of different sensor types. A novel signal processing method for quartz crystal sensors in combination with road deflection and temperature outputs allows a better evaluation of wheel road interaction regarding on the dynamic impact of vehicles. Both systems were calibrated using three different vehicle types: axle, axle and axle, full and half loaded (see tab.). The applied method validity of measuring can get a warranty for a fair direct enforcement of overloaded vehicles based on the WIM measuring. Accelerometer and temperature gradient outputs are used improve the axle load calculation in relation to actual road deflection. The below examples shows the results of system approval test provided by CMI. The results for three sensor configurations (layouts) show relatively small difference. One explanation is probably the high quality of a special road pavement (class excellent, acc. pren). Additional factors are the exact measuring of wheel position and also the algorithm with new implemented correction factors Table Calibration vehicles veh. veh. config. suspension GVW V V V N N N N N axles springs ax. veh. + ax. trailer ax. tractor + ax. semitrailer springs / air air [kg] [km/h] [km/h] [km/h] [kg] [kg] [kg] [kg] [kg] '0 0 0 '99 ' ' 0 0 '9 0'0 '0 0 0 '0 ' '0 ' 0' ' 0' ' ' ' ' ' ' '0 ' ' ' 0'00 '99 ' '90 W approval LPR & overview cameras Accelerometer Temperature sensor Lineas quartz crystal sensor Wheel position, twin tyre detection Inductive loop WIM system configuration: quartz crystal sensor rows ( x Lineas à cm), MSI sensor angle of, temperature sensors for temperature gradient, accelerometer sensor 9

10 A B C D E F G H I J M O P Q Conditions () Test plan Env t Initial verification (Yes=, No=0): 0 rr I SYSTEM Number Identified Mean Std deviat π o Class δ δ min δ c π Accepted Entity (%) (%) (%) (%) (%) (%) (%) (%) class gross weight A() group of axles A() A() single axle A() axle of group A() % 0 delta min delta c gross weight group of axles single axle axle of group Criterion W approval LPR & overview cameras Accelerometer Temperature sensor Lineas quartz crystal sensor Wheel position, twin tyre detection Inductive loop WIM system configuration: quartz crystal sensor rows ( x Lineas à cm), MSI sensor angle of, temperature sensors for temperature gradient, accelerometer sensor A B C D E F G H I J M O P Q Conditions () Test plan Env t Initial verification (Yes=, No=0): 0 rr I SYSTEM Number Identified Mean Std deviat π o Class δ δ min δ c π Accepted Entity (%) (%) (%) (%) (%) (%) (%) (%) class gross weight A() group of axles A() A() single axle A() axle of group A() % 0 delta min delta c gross weight group of axles single axle axle of group Criterion 0

11 W approval WIM electronic cabinet, TCP/IP LPR & overview cameras Accelerometer Temperature sensor Lineas quartz crystal sensor Wheel position, twin tyre detection Inductive loop WIM system configuration: quartz crystal sensor rows ( x Lineas à cm), MSI sensor angle of, temperature sensors for temperature gradient, accelerometer sensor A B C D E F G H I J M O P Q Conditions () Test plan Env t Initial verification (Yes=, No=0): 0 rr I SYSTEM Number Identified Mean Std deviat π o Class δ δ min δ c π Accepted Entity (%) (%) (%) (%) (%) (%) (%) (%) class gross weight A().. 9. group of axles A() A() single axle A().. 9. axle of group A() % 0 delta min delta c gross weight group of axles single axle axle of group Criterion Literature CMI CZ Measure of a general nature, No. 0-OOP-C00-0, ref. No. 0/00/0/Pos., May 00 OIML R- "Automatic instruments for weighing road vehicles in motion and measuring axle loads Part : Metrological and technical requirements Tests" available to the public at pren (NN nnnnn) Weigh in Motion of road vehicles, Version 00/ Ministry of Transport and Communications Decree No. /00 Coll., on approving technical competence, and on technical conditions for operating vehicles on the road network, as amended Doupal E. Technical standard proposal for WIM systems, Road administration CZ, May 00