Analysis of Crash Causes, Costs, and Countermeasures in Alabama Work Zones

Transcription

1 1 2 Analysis of Crash Causes, Costs, and Countermeasures in Alabama Work Zones Virginia P. Sisiopiku*, Ph.D. Associate Professor. Civil, Construction and Environmental Engineering. University of Alabama at Birmingham th St S, HOEN 311B, Birmingham, Alabama, Phone: (205) , Fax: (205) , vsisiopi@uab.edu Ossama E. Ramadan, M.A.Sc. Doctoral Candidate. Civil, Construction and Environmental Engineering. University of Alabama at Birmingham. oramadan@uab.edu Mohammed I. Eltaher Ismail, M.S.C.E, Civil, Construction and Environmental Engineering. University of Alabama at Birmingham. elhowary@uab.edu Ozge Cavusoglu, Ph.D. Research Associate. Civil, Construction and Environmental Engineering. University of Alabama at Birmingham. ozge@uab.edu ABSTRACT Work zone traffic safety is an important issue as it affects safety of drivers, passengers, and construction workers. In addition, the recent rise in scheduled construction activities necessary to maintain function of highways aggravates the issue. Still, little is known about actual conditions and causes for crashes at work zones in Alabama. Thorough the past five decades, only four studies were performed to investigate crashes in Alabama work zones. The purpose of this study is to investigate crashes in Alabama work zones to identify causes, estimate costs, and research potential countermeasures. The study analyzed Alabama crash records within the five year period from 2008 to Analysis was performed using the Critical Analysis Reporting Environment (CARE) that has been developed by the Center for Advanced Public Safety at the University of Alabama. Posted speed limit, lighting in dark conditions, work zone traffic control, and human factors were identified as key factors for crashes in Alabama work zones. Costs were reported and countermeasures were identified and summarized. This study is significant for its contribution to existing literature in investigating highway work zone crashes, which will enables researchers to identify unique work zone safety problems. Accordingly, effective countermeasures could be implemented with a potential to save lives of drivers, passengers, and construction workers in the future. Keywords: Crashes, Work Zone Safety, Crash Causes, Countermeasures, Traffic Safety * Corresponding author

2 Sisiopiku et al INTRODUCTION In recent years, the focus of many states has shifted from building new highways to maintenance and rehabilitation, which gives rise to scheduled construction activities at work zones. Such activities mandate lane closures and disruption of traffic to provide a work space (1). A recent report, cited by Yang et al. (2), stated that approximately twenty percent of the U.S. highways are under construction during the peak construction season, which involve over three thousand work zones. About twelve billion vehicle miles of travel a year will be through active work zones and travelers can expect to encounter an active work zone one out of every hundred miles driven on the highway system. Consequently, about 24 percent of the non-recurring delays and 10 percent of overall delays on freeways were attributed to work zones and 87,606 crashes occurred in work zones that led to over 37,000 injuries and 576 fatalities during Table 1 summarizes work zone related fatalities in the US within the period 2008 to 2012 (3). Drivers and passengers represented 85% of those killed in work zone crashes (4). While the majority of victims are drivers, the National Safety Council reports (5), show that more than 100 road construction workers are killed in construction zones every year, 5 of which are killed by motor vehicles. Table 1: Work Zone Related Fatalities in the US, (7) Total US Work Zone Related Crashes , Driver distraction and excessive merging are usually cited as the main cause of work zone crashes; however, unlike other non work zone related safety studies, there has not yet been a comprehensive review and assessment of methodological approaches for work zone safety (2). Mitigating mobility and safety impacts of work zones has become one of the overwhelming challenges that traffic engineers and researchers have to confront (6). Studying the characteristics of work zone crashes is the first step towards improving work zone safety. Investigating highway work zone fatal crashes enables researchers to identify unique work zone safety problems. Accordingly, effective countermeasures could be developed to save lives of drivers, passengers, and construction workers. Literature was expected to be abundant on such demanding topic. Yet, there is a challenge in identifying literature that strictly differentiates between work zone related and non-work zone related crashes. Recently, Yang et al. (2) performed an extensively comprehensive literature review of work zone crash data analysis and modeling. They identified 81 articles within the period 1962 to 2013 that studied work zone related crashes, four of which were concerned with Alabama. Evidently, there is a deficiency in research of crashes in Alabama work zones. To overcome this deficiency, this study presents an analysis of the causes of crashes in Alabama work zones, and investigates potential countermeasures. Analysis spanned over a five years period, and attention was given to contributing factors and conditions present at work zone crash locations. Appropriate engineering, education, and enforcement countermeasures were proposed in order to address the work zone safety issue in the future.

3 Sisiopiku et al METHODS For the analysis period, 2008 to 2012, Alabama had an average of 888 fatalities in crashes, of which an average of 10 fatalities were work zone related (7). A recent analysis indicated that construction workers are the victims on nearly 16% of all crash fatalities at work zones (8). In addition, a comparison between the ratios of work zone crash fatalities to all crash fatalities revealed that Alabama has 43.4% less fatalities than all US. Still, as the Alabama traffic safety community is moving toward a Zero Deaths goal, efforts have to intensify to reduce the number of fatalities in Alabama roadways and eliminate fatal crashes at work zones in the years to come. In doing so, better understanding of contributing factors to such crashes is important in developing engineering, education, and enforcement strategies for meeting the Zero Deaths goal. Analysis of historical crash data in Alabama was performed to determine the extent of work zone crashes and identify relevant risk factors. Crash records focusing on work zone related crashes were analyzed using Critical Analysis Reporting Environment (CARE) over the five year period, 2008 to CARE is a data analysis software package developed by the Center for Advanced Public Safety at the University of Alabama and is designed for problem identification and countermeasure development in traffic safety applications (9). The records on CARE are constructed based on the police reports that were filled out at the crash sites and provide detailed information about the conditions that contributed to the crash and severity. CARE provides filters, based on which, specific records can be obtained including work zone presence. Using such records, charts and graphical displays were produced for selected variables in the database. Using CARE capabilities, summary information for the subset of the database that related to work zone crashes over the 5-year study period was retrieved. Table 2 lists five main categories defined by 23 variables that were considered in the analysis, which include responsible driver information, time of occurrence, climatic environmental information, crash type and related information, and roadway conditions (9). Frequency output of any variable or a cross-tabulation of any two variables was used to process the data and help to understand and interpret them. 98 Table 2: Main Categories of Work Zone Crash Data in CARE Category Responsible Driver Time Information Climatic Environment Crash Information Roadway Condition Variables Age; Gender Time; Day; Month; Year Light Condition; Weather Condition; Road Surface Condition Vehicle Maneuver Before Crash; Crash Severity; Crash Type; Vehicle Body Type; Number of Vehicles Involved Road Class; Road Character; Number of Lanes; Speed Limit; Crash Location; Surface Type; Road Special Feature; Area Information; Traffic Control

4 Sisiopiku et al RESULTS AND DISCUSSION This section presents the analysis results and discussion of crash causes, costs, and countermeasures. Understanding the crash causes, and associated costs, as well as potential countermeasures will facilitate further research of work zone crashes in an effort towards a zerodeaths policy. Crash Causes Responsible Driver Information This category includes basic information about the driver responsible for the crash occurrence. Age and gender were the two variables related to responsible driver category. Age was divided into seven groups and gender contained two types: male and female. Figure 1 presents the age distribution of the drivers responsible for work zone crashes between 2008 and 2012 in the state of Alabama. The results show that age group years had the highest share of work zone crashes with 18.9%, followed by years with 16.2%, and years had 14.2%. With respect to gender, approximately 58% of the drivers responsible for work zone crashes were males and 37% were female drivers, with 5% reported as unknown. 2 15% 1 5% Figure 1: Age Distribution of Responsible Drivers Time Information This category included time-related information such as the time and date of the crash occurrence. Figure 2 shows the work zone crash distributions by hour. Results indicate that the highest crash frequency at work zone sites occurred during the daytime non-peak period 10:00am to 4:00pm, with 937 crashes/hr reported over the study period. In addition, 662 crashes/hr were reported during the AM peak (6:00 to 9:00am), and 676 crashes/hr were reported during the PM peak (4:00to 8:00 pm). Furthermore, results indicate that most work zone crashes occur from 3:00-4:00 pm (8.9%) followed by the lunch break, noon-1:00 pm (7.5%). Surprisingly, nighttime crashes (i.e., those occurring from 12:00-6:00 am and 8:00-12:00 am combined) were much lower (only 197 crashes/hr). These results were contrary to the expectation that typically associates heavier traffic and nighttime conditions with increased crash risk. Age 128

5 Sisiopiku et al % 6% 4% 2% :00-12:59 am 1:00-1:59 am 2:00-2:59 am 3:00-3:59 am 4:00-4:59 am 5:00-5:59 am 6:00-6:59 am 7:00-7:59 am 8:00-8:59 am 9:00-9:59 am 10:00-10:59 am Figure 2: Work Zone Crash Distributions over Time of Day 11:00-11:59 am Noon-12:59 pm Time of Occurence 1:00-1:59 pm 2:00-2:59 pm 3:00-3:59 pm 4:00-4:59 pm 5:00-5:59 pm 6:00-6:59 pm 7: pm 8:00-8:59 pm 9:00-9:59 pm 10:00-10:59 pm 11:00-11:59 pm Figure 3 illustrates the distribution of work zone crashes by month of year. As expected, more crashes occurred between April and November, a period that coincides with the roadway constructions season in Alabama. 1 8% 6% 4% 2% Month Figure 3: Distribution of Work Zone Crashes by Month of the Year Climatic Environment Information The climatic environmental information refers to the environmental conditions such as light, weather, and road surface conditions at the work zone site when the crash happened. In CARE, light conditions included 14 types based on the factors that affecting visibility like natural brightness (e.g., daylight, dusk, dawn, and darkness) and streetlight. Weather conditions were

6 Sisiopiku et al considered in 13 weather types that might have impacts on traffic safety such as clear, cloudy, fog, mist, rain, sleet, snow, windy, etc. Road surface conditions also consider 13 types to reflect the situations of road surfaces. Results show that 76% of the work zone crashes happened in daylight conditions, as illustrated by Figure 4. Under dark conditions, 1,411 work zone crashes were reported when the roadway was not lighted, compared to 472 crashes when the roadway was lighted. This indicates the importance of providing additional lighting at work zones operating at nighttime to reduce the likelihood of crashes occurrence % Daylight Dusk Dawn Dark-Roadway Lighted Dark-Roadway Not Lighted Dark-Unknown Roadway Lighting Light Conditions Dark-Spot Illumination One Side of Roadway Dark-Spot Illumination Both Sides of Roadway Dark-Continuous Lighting One Side of Roadway Figure 4: Work Zone Crash Distributions Based on Light Conditions Dark-Continuous Lighting Both Sides of Roadway Another factor considered in the analysis was weather conditions. The crash data analysis indicated that 67.2% of crashes in work zones happened in clear weather, 20.8% under cloudy conditions, and 9.8% under rainy conditions. As for the effect of road surface conditions on work zone crashes, results indicate that 84.3% of crashes in work zones occurred when road pavement was dry and only 14.3% of total crashes occurred when the road was wet, with minimal attribute to ice and snow due to Alabama ambient weather conditions. Crash Information The crash information category for work zone crashes in CARE includes vehicle maneuver before crash, crash severity, crash type, vehicle body type, and number of vehicles involved. The before-crash vehicle maneuver includes several values such as going straight, changing lane,

7 Sisiopiku et al slowing down, overtaking another vehicle, etc. The crash severity has three classical types, namely fatal, injury, and property damage only severity classifications. Other crash types include single vehicle crashes, rear end crashes, and sideswipe crashes, among others. The vehicle body types were classified into many categories such as heavy trucks, passenger cars, motorcycles, etc. The number of vehicles involved in a crash was considered using the actual number of vehicles on record. Results indicate that approximately 58% of crashes occurred while the vehicle was moving straight before the crash and 1 happened while the vehicle was slowing or stopped. Approximately 6% of crashes took place as the main vehicle was changing lanes and another 6% while the vehicle was turning left. In addition, results show that 48% of work zone crashes in Alabama involved passenger cars and 24% involved pick- up trucks (four-tire light trucks), while only 4.3% involved tractors or semi-trailers. These results indicate the misconception of overrepresenting trucks in work zone crashes. Figure 5 summarizes work zone crashes by crash type, and indicates the most frequent type of collision at work zones involving two vehicles is the rear end collision with 32% followed by sideswipe collision with 8%. Rear end collisions are often associated with lower travel speeds while the sideswipe collisions are associated with lane changing/merging maneuver. It is also observed that the single vehicle crashes account for 1 out of every 7 work zone crashes, or 15%. These results suggest that taking strong measures to prevent rear end crashes as well as single vehicle crashes would greatly improve the safety of work zones in the future. 35% 3 25% 2 15% 1 5% Crash Type Figure 5: Work Zone Crashes by Crash Types As illustrated by Figure 6, the majority of work zone crashes in Alabama are property damage only crashes representing 77.8%, followed by incapacitating injury (7.), possible injury (6.5%), and non-incapacitating injury (6.8%). Over the study period, 84 fatal crashes occurred representing 0.65% of the total work zone crashes. These numbers show that while thousands of crashes occur at work zones every year, the vast majority of them are property damage only. Still

8 Sisiopiku et al Fatal Injury Incapacitating Injury Non-Incapacitating Injury Possible Injury Property Damage Only Crash Severity Figure 6: Severity Type of Work Zone Crashes improvements can be made to reduce the total number of crashes at work zones and the occurrence of crashes that involve injuries and fatalities. Road Conditions The following Road Conditions were considered in the analysis: i. Road class is represented by seven types in crash reports. Results indicate that most crashes happened on interstate highways with 41.5%, followed by federal highways with 21.7%. ii. Road character has seven types that describe details about the geometric alignment of a crash section such as curvature and grade. Results indicate that 62.1% of work zone crashes occurred on a level terrain, 13.5% occurred on downgrades, and 11.3% occurred on upgrades. Results further indicate that the proportion of work zone crashes on curves is small. iii. Number of lanes: Results indicate that 45.5% of crashes happened on four lane highways and 29. of them on two lane highways. iv. Speed limit: Figure 7 presents the posted speed limits at work zone crashes in Alabama during the study period. Results show that there is insignificant difference between the numbers of crashes occurring at 45 mph speed limit and those that occur at 55 mph speed limit. However, a speed limit of 35mph resulted in reduction of the number of crashes by more than 5. It can be concluded that, while a moderate reduction of the speed limit (from 55 mph to 45 mph) has little to no impact on traffic safety at work zone sites, a more drastic reduction (35 mph) is associated with a significantly lower crash risk.

9 Sisiopiku et al % 2 15% 1 5% Speed Limit Figure 7: Posted Speed Limits at Work Zone Crash Locations v. Traffic control is represented through 11 types of traffic control devices. Results indicate that half of all crashes in work zones occurred at sites that were not controlled. Accordingly, absence of traffic control can be viewed as a contributing factor in work zone crashes. In addition, proper work zone traffic control may have a positive impact on traffic safety at work zones. Crash Costs Crash costs at work zones are difficult to assess due to the wide range of cost categories and items involved in such crashes. Coburn et al. (10) conducted a comprehensive study to estimate costs associated with crashes at work zones. Their average comprehensive results were $542,533 for incapacitating crashes in work zones, $147,536 for non-incapacitating crashes, and $86,943 for possible injury crashes. Their study excluded fatal crashes due to relatively small sample sizes, and PDO crashes were defaulted to the FHWA value of $10,956, all in 2010 USD. Countermeasures Analysis of crashes in Alabama work zones for the period 2008 to 2012, provided valuable insight about the nature of such crashes. The most relevant causes of crashes in Alabama work zones were found to be: Posted speed limit Lighting in dark conditions Work zone traffic control, and Human factors Countermeasures that consider these causes are likely to result in improved traffic safety in Alabama work zones. Table 3 summarizes these countermeasures in three categories: engineering, education, and enforcement, through evaluating 5 risk categories of work zone crashes.

10 Sisiopiku et al Table 3: Work Zone Safety Improvement Recommendations Risk Type Risk Description Safety Improvement Recommendation High-risk drivers High-risk time periods High-risk locations Most common crash types Driver errors Male drivers Drivers between Daytime peak hours (06:00 10:00 am and 03:00 7:00 pm) Nighttime (8:00 pm 6:00 am) Slow-construction season (November March) Urban interstate 4-lane highways; Speed limits from 45 to 55 mph Complex geometric alignments Multi-vehicle collisions (rear-end) Truck involved crashes Inattentive driving Safety education Safety education Safety education and traffic control enforcement Illumination or retro-reflective devices Routine traffic control inspection and public information Effective speed control devices and speed limit enforcement Developing special traffic controls for complex geometric alignment Effective speed control devices and speed limit enforcement Safety education, speed control, and work-zone geometric design with enough space for heavy truck maneuver Devices such as flashing lights or temporary raised pavement markers in the advance warning area 241 Misjudgment/disregarded traffic controls Traffic control enforcement and avoiding confusing traffic control signs/signals The following sub-sections briefly discuss the proposed counter measures as presented in the aforementioned table. Engineering Clear guidance to drivers through proper signage and efficient work zone traffic control strategies are expected to have a major positive impact on traffic safety at work zones. Dynamic work zone traffic control and dynamic merge control strategies that adapts to traffic flow conditions should be considered whenever and wherever feasible. In addition, there is an apparent need for innovative speed limit enforcement solutions in work zones. Maintaining

11 Sisiopiku et al relatively low speeds throughout the work zone (35 mph when appropriate) is important for protecting construction workers and the traveling public, and reducing the severity of potential crashes. The dominance of rear-end collisions in injury crashes indicates a strong association between speeds and work zone crashes. Improved visibility is an important factor for traffic safety at work zones in Alabama. It is recommended to install additional illumination or reflector devices in work zones to improve the visibility under dark conditions. In addition, temporary raised pavement or transverse markings may help to alert drivers in advance when approaching work zones. Traditional methods like flags and flasher arrows should not be ignored. Education Driver errors are a major contributing factor to all traffic crashes, including work zone related crashes. Therefore, driver education is important to raise awareness of safe driving practices at work zones. Training programs and courses that teach drivers about the consequences of reckless driving, in general, and the importance of complying with work zone regulations, in particular, are recommended. Increasing knowledge and awareness of work zones by disseminating work zone safety information to travelers is also important. Work zone awareness campaigns are also recommended to help inform the public about the complexities of driving through work zones and the importance of compliance with work zone regulations. Enforcement Drivers tend to strictly abide by traffic laws when the presence of traffic law enforcement is perceived. In addition, the perceived presence of traffic law enforcement provides traffic calming effect similar to that provided by traffic calming devices. The need for innovative enforcement techniques, tools, and technologies is evident. Enforcement costs are significant within any agency or project, and this adds to the challenge of the development of cost-effective enforcement strategies. However, enforcement should be used to achieve a specific objective, and the implementation strategy should be consistent with that objective (11) CONCLUSION Crash records in Alabama work zones were analyzed for a 5 years period to present a clear and objective understanding of the nature of crashes in Alabama work zones. Results show that the vast majority of crashes occurring in Alabama work zones are property damage only. Still, given the commitment of the state of Alabama toward Zero Traffic Deaths, additional engineering, education, and enforcement improvements can be made to reduce the total number of crashes at work zones and the occurrence of crashes that involve injuries or fatalities. Specifically, the analysis showed that rear end crashes are the most common type of work zone crashes in Alabama. Moreover, the frequency of crashes in work zones with speed limits above 35 mph was significantly higher. These findings pinpoint to an association between high speeds and work zone crash occurrence. To address this issue, better speed control at work zone is recommended through appropriate traffic control and enforcement strategies. The analysis also revealed that under dark conditions, lack of lighting contributes to an increase in the frequency and severity of crashes. This finding shows the importance of providing good lighting at work zones operating in the evening and night hours in order to reduce the likelihood of crash

12 Sisiopiku et al occurrence. In addition, it was observed that most of the work zone crashes occur due to driver errors. Accordingly, driver education and training on proper driving behavior at work zones is essential in preventing such crashes. Moreover, results emphasize the importance of traffic control, as it is the single most important measure that can be implemented to address traffic safety concerns at work zones. This paper serves as a useful reference to transportation stakeholders interested in improving work zone traffic safety for workers, motorists, and other highway users through work zone design and control interventions and increased motorists awareness and compliance to work zone regulations. REFERENCES 1. Wei, H. et al. Synthesis of Unconventional Dynamic Merge Metering Traffic Control for Work Zones. Open Transportation Journal, Vol. 4, 2010, pp Yang, H. et al. Work Zone Safety Analysis and Modeling: A State-of-the-Art Review. Proceedings of the Transportation Research Board 93rd Annual Meeting, Washington, DC, Rocky Mountain Insurance Information Association. Construction Zone Safety Federal Highway Administration. Work Zone Safety for Drivers. Publication FHWA-SA Federal Highway Administration, Washington, DC, ADTSEA Driver Education Curriculum 2.0. The American Driver and Traffic Safety Education Association (ADTSEA), Bai, Y. and Y. Li. Determining Major Causes of Highway Work Zone Accidents in Kansas. Publication KU Kansas Department of Transportation, Topeka, Kansas, American Road and Transportation Builders Association (ARTBA) and Texas A&M Transportation Institute (TTI). The National Work Zone Safety Information Clearinghouse, Work Zone Fatalities: Work Zone Fatalities by Year and State Pegula, S. M. An analysis of fatal occupational injuries at road construction sites, Monthly Labor Review, 2013, Retreived from 9. Critical Analysis Reporting Environment (CARE), Ver Center for Advanced Public Safety, Tuscaloosa, AL, Computer Software. 10. Coburn, J. S. et al. Injury Outcomes and Costs for Work Zone Crashes. Proceedings of the Transportation Research Board 92nd Annual Meeting, Washington, DC, Ullman, G. L. et al. Traffic Enforcement Strategies for Work Zones. National Cooperative Highway Research Program (NCHRP) Reports, Publication 746. Transportation Research Board, Washington, DC, 2013.