Spatial Distribution and Characteristics of Accident Crashes at Work Zones of Interstate Freeways in Ohio

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1 Proceedings of the IEEE ITSC IEEE Intelligent Transportation Systems Conference Toronto, Canada, September 17-2, 26 WB7.5 Spatial Distribution and Characteristics of Accident Crashes at Work Zones of Interstate Freeways in Ohio O.M. Salem, Ash M. Genaidy, Heng Wei, and Nitin Deshpande Abstract In this paper, we identify the spatial distribution and characteristics of fatal and injury at different work zone locations on interstate freeways in Ohio within the last three (3) years. Work zone accident data obtained from the Ohio Department of Public Safety and Ohio Department of Transportation from year 21 through 23 has provided necessary information for the analysis. The study provides an insight on fatal and injury at different locations within work zones. Concentrating only on fatal and injury allowed for evaluation of the predominant factors that are responsible for these types of. The results indicate that there is a significant difference in the proportion of fatal and injury as well as rear-end at different locations within a work zone. The activity area comes out to be the most dangerous area in a work zone and safety efforts must be concentrated on this area to improve the work zone safety. Predominance of rear-end at all locations within a work zone indicates a high speed variance. Any countermeasures to reduce the speed variance will definitely improve the work zone safety. Keywords Work Zone Safety, Crashes,, Injury Accidents, Traffic Safety, Rear-End Crashes, Proportionality Tests. I. INTRODUCTION ORK zone safety continues to be a high-priority issue Wfor traffic engineering professionals and for highway agencies. Emphasis on improving the identification of work zone problems, especially those related to safety issues has been increased in recent years. Traffic accidents in highway work zones are a continuing problem. Work zones tend to cause hazardous conditions for drivers and highway workers. The adjacent roadside is usually occupied by construction barriers, construction machinery, warning devices, and workers. The drivers are also required to follow a number of instructions conveyed by a variety of traffic control devices. In addition, there will be lane closures resulting in reduction of roadway capacity. The effect of these restrictions is congestion, increased Manuscript received March 2, 26 O.M. Salem is with the Department of Civil & Environmental Engineering at the University of Cincinnati, Cincinnati, Ohio 45221, USA (phone: ; fax: ; osalem@uc.edu). A. M. Genaidy is with the Department of Industrial Engineering at the University of Cincinnati, Cincinnati, Ohio 45221, USA (phone: ; ash.genaidy@uc.edu). H. Wei is with the Department of Civil & Environmental Engineering at the University of Cincinnati, Cincinnati, Ohio 45221, USA (phone: ; fax: ; heng.wei@uc.edu). N. Deshpande is with the Department of Civil & Environmental Engineering at the University of Cincinnati, Cincinnati, Ohio 45221, USA. delay, driver frustration which ultimately leads to safety problems. Work zone safety has been a national concern for several years. Work zone accidents are a major concern and point out the need for continuous emphasis on the safety of motorists driving through the work zones. In 23, 459 injury and 1 fatal accidents were reported at interstate freeway work zones in Ohio. Figure 1 indicates the trend in work zone accidents for the past three years (21through 23) in Ohio. As vehicle miles traveled (VMT) continues to increase significantly faster than miles of roadway, work zones exacerbate the growing congestion and safety problem. Between 198 and 2, highway lane miles increased 2.4 percent while vehicle miles of travel grew by 8 percent. Work zone fatalities reached a high of 1,79 in 21, and over 4, people are injured in work zone related each year. The statistics indicates that accidents in construction zones are increasing at an alarming rate. Thus construction zone safety has become a priority issue for the FHWA as well as most state departments of transportation (DOT s). The Transportation Equity Act for the 21 st Century (TEA 21) provides increased funding for rehabilitation, reconstruction and maintenance of existing highway system. With the passage of federal legislation TEA-21, the number of work zones is expected to increase significantly, this may lead to a dramatic escalation in the number of work zone accidents. Reconstruction and maintenance activities will continue in the future and driving through work zones will continue to be an everyday experience. It is very clear from the above statements that detailed studies of fatal and injury work zone, from the traffic point of view will be helpful in determining the predominant factors responsible for the work zone accidents. The factual information obtained from such analysis of data will be helpful in reducing fatal and non-fatal work-zone accidents. II. OBJECTIVE The objective of this project is to identify the spatial distribution and characteristics of fatal and injury accidents within all type of interstate work zones in Ohio within last three (3) years. Proportionality tests are used to examine the significance of crash distributions. Also, the authors analyzed driver roadway and work zone conditions related to fatal and injury accidents /6/$2. 26 IEEE 1642

2 III. PREVIOUS STUDIES Analysis of fatal work zone accidents is a complex issue due to a large number of contributing factors that are responsible for the work zone accidents. Pigman and Agent (199) indicated that several factors are responsible for increases in the number of at construction work zone sites such as such as type of work zone (construction, maintenance, utility maintenance or utility, undetermined), location in work zone, type of accident, vehicle type, light condition and lane use. The authors found that, in general, work zone accidents are more severe than other accidents with a high percentage of rear-end and sideswipe accidents; following too close was the most frequently listed constributing factor. Lorenz and Hall (1989) conducted a study to improve the safety of highway construction zones in New Mexico and examined construction zone accidents for a period of 3 years and made a comparison of driver, roadway and environmental characteristics of accidents before and during construction. Lorenz et al. concluded that some accident characteristics such as rear end accidents are typical for the construction zones. They also ruled out the influence of adverse weather conditions as being responsible for the increase in work zone. Pal and Sinha (1996) conducted an analysis of crash rates at interstate work zones in Indiana. The statistical analysis of the data using non- Bayesian approach was carried out to analyze the effect of an activity on crash reduction. The authors found that crash rates in work zones are on the higher side than those on comparable highway sections without work zones. A 3 year period study of NYSDOT construction projects carried out by Bryden, Andrew et al. (1998) examined work zone traffic accidents involving construction-related items. The items included traffic control devices (TCDs), safety features, pavement and roadside features, such as bumps, edge drop-offs, excavations, etc. and construction vehicles, equipments and workers. The authors concluded that good design of work zone traffic plans, combined with adequate training and supervision of workers is essential to address the issue of work zone safety. A detailed study of accident experience in construction and maintenance zones by Ha and Nemeth (1995) presents a summary of findings from 1 studies on accidents in construction work zones. The authors concluded that certain type of accidents at a given work zone can suggest specific problems with traffic control plans and/or with the implementation of the plans. A study carried out by Garber and Zhao (22) at different work zone locations in Virginia concluded that activity area is the most prevalent accident location in a work zone, and the termination area is the safest area in a work zone. The study also concluded that rear-end is the most predominant collision type. Bryden and Andrew (2) analyzed the intrusion accidents on highway construction projects in New York State over a six year period and concluded that excessive speed and driver inattention are major factors responsible for intrusion accidents. Another study carried out by Benekohal, Shim et al. (1996) in Illinois State to determine truck drivers concerns about traffic control in work zones and to identify the locations of accidents and risky driving situations included a statewide opinion survey of 93 semi-trailer drivers. The survey contained questions about driver/vehicle characteristics, assessment of work zone traffic control devices, accident and difficult driving situations, and suggestions for improving traffic flow safety in work zones. It was found that about 9% of truck drivers consider traveling through work zone to be more hazardous than non-work zone areas. About half of them want to see an advance warning sign 5 to 8 kilometers (3 to 5 miles) ahead of work zone. The authors concluded that the accident experiences were significantly related to the experience of bad driving situations but not other driver/truck characteristics. A study by Wang, Hughes et al. (1996) mentioned the need of uniform definition of work zone type and work zone crash in order to determine the magnitude of the work zone safety problem, to monitor trends and develop crash rates, and to identify improved treatments based on the analysis of the work zone accident characteristics. The authors also discussed deficiencies of data reporting practices and issues of data needs pertaining to work zone safety. Bryden and Andrew (2) analyzed two hundred and ninety intrusion accidents that were reported on New York State Department of Transportation highway construction projects over a six year period from 1993 through The authors investigated the characteristics of intrusion accidents and locations where they occurred. These intrusion accidents were compared with other traffic and construction accidents. The authors concluded that excessive speed, driver incapacity-due to alcohol use, lack of sleep, medical problems, vehicle failure, or roadway conditions and driver inattention are major factors responsible for intrusion accidents. IV. DISCUSSION Many other studies have been performed on accident experience within work zones in the United States. However, most of these studies have investigated all (fatal, injury and property damage only ) within a work zone. Property damage only (PDO) account for about 6% of all work zone accidents and thus overshadows the effect of fatal and injury accidents. These studies also take an approach of comparing work zone accidents with the accidents at non-work zone locations and provide relevant information on the difference between accident rates at work zone and non-work zone locations, although fatal and injury have not been the focus of the study. This study, in contrast to other studies focuses only on fatal and injury accidents at interstate freeways in Ohio to determine the potential safety hazards in different type of work zones. 1643

3 V. DATA On July 1, 2 the Ohio Department of Public Safety (ODPS) launched their new OH-1 crash report form statewide. These new data have forced a change in both ODPS's and Ohio Department of Transportation s (ODOT) crash data structures. The new format provides more detailed information about the crash and will be helpful in finding out the most predominant factors that contribute to work zone accidents at work zones. Information on each work zone crash that occurred from 21 through 23 was obtained from the Ohio Department of Public Safety and the Ohio Department of Transportation. The were studied to determine the highway type and type of work zone. Only those that occurred at interstate freeways were carefully selected from the crash data. VI. METHODOLOGY The that occurred at interstate freeways in Ohio from 21 through 23 were selected for the study. The location of a crash was further subdivided into the following work zone areas as identified by Manual on Uniform Traffic Control Devices (Refer figure 2): (a) Advance warning area, (b) Transition Area, (c) Activity Area, (d) Termination Area. Crashes that occurred before work zone warning sign were also considered for the study. Crash reports were further studied to evaluate type of collision (rear-end, headon, angle, sideswipe etc.), weather condition (clear, cloudy, rain, snow), roadway condition (dry, wet), light condition (daylight, dawn, dusk, dark), type of road contour (straight, curve), pre-crash actions and type of traffic control. Percentage distributions were determined for the type of collision, and location of crash. In order to determine the significance of distributions, proportionality tests (Scheaffer & McClave, 1994) were carried out at 95 % significance level. Proportionality tests can be used to test the null hypothesis that two proportions or binomial parameters are equal. For example, we might try to prove that the proportion of by collision type is the same for all locations within the work zone area. The following null hypotheses were tested: The proportion of injury is the same at each location within a work zone. The proportion of rear end collision is the same at each location within a work zone. VII. OHIO FATAL AND INJURY CRASH SUMMARY Figure 1 shows the number of fatal and injury during the period between 21 and 23. During this period, a total of 1448 fatal and injury occurred within interstate work zones including 34 fatal and 1414 injury accidents. Crash reports for fatal and injury accidents in Ohio are completed by state or local police. The crash report includes information on the presence of work zone and type of work zone. Crashes Injury Year Fig 1: Work Zone Injury & Crashes at Interstate Freeways Fig 2: Areas in a Construction Work Zone (Source: Manual on Uniform Traffic Control Devices 2) 7.1 Location Distribution As shown in Figure 3, 62% of the injury and fatal accidents at interstate freeways in Ohio occurred within activity area. Thus it can be concluded that the activity area is the most dangerous area within a work zone followed by the advance warning area where 13% of fatal and injury accidents occurred. Proportionality test was performed at a significance level of.5 to determine whether the proportion of injury at each location within a work zone is significantly different from the proportion at the other locations. The results of the test are presented in Table 1. The proportionality test results indicates that the proportion of fatal and injury in the advance warning area are on the higher side as compared to other work zone locations. 1644

4 Rear End Single Vehicle Collision Sideswipe-Same Direction Angle Work zone area (a) Work zone area (a) (X 1 ) + Injury (n1) (X 2 ) areas + Injury (n2) Before work zone warning sign Advance warning area Transition area Activity area Table 2: Proportionality test results between rear-end in each area and rear-end in other areas Fig 3: Collision Distribution 7.2 Manner of Collision As shown in Figure 4, the predominant type of crash collision occurring within interstate work zones in Ohio is the rear-end collision. This type of collision comprises 52% of the total fatal and injury. Proportionality test was performed at a significance level of.5 to determine whether the proportion of rear end collision at each location within a work zone is significantly different from the proportion at the other locations. The results of the test are presented in Table 2. The test results indicates that the proportion of rear-end in advance warning area and the area before the work zone sign is on the higher side as compared to the proportion of rear-end accidents in transition area and activity area. Single vehicle accidents account for 32% of fatal and injury at interstate freeways. Angle and sideswipesame direction accidents represent the second predominant types of collisions between two vehicles. These types of collisions represent about 14% of fatal and injury at interstate freeways. and Injury Accidents (%) Upstream Advance Warning Fig 4: Location Distribution Work zone area (a) Transition Activity Work zone area (a) (X 1 ) + Injury (n1) Termination Non-workzone (X 2 ) areas + Injury (n2) Before work zone warning sign Advance warning area Transition area Activity area Table 1: Proportionality test results between fatal in each area and fatal + injury in other areas 7.3 Vehicle Type and Light Conditions and injury within interstate work zones in Ohio primarily involved passenger vehicles. These vehicles account for 71% of the vehicles involved in fatal and injury. Trucks are involved in 25% of the. About 61% of the fatal and injury accidents within interstate work zones occurred during daylight condition. 15% of the fatal and injury accidents took place during dark conditions. Figure 5 shows the distribution of fatal and injury accident at interstate freeway work zones in Ohio under various light conditions Daylight Dark-Lighted Roadway Dark-Roadway Not... Dawn Fig 5: Distribution of Light Condition 7.4 Roadway Characteristics A higher proportion of fatal and injury in Ohio interstate work zones occurred on the level roadway when Dusk 1645

5 the roads were dry. About 75% of the accidents occurred when the road was dry and about 67% of the accidents occurred on a straight leveled road. Figures 6 through 8 show the distribution of fatal and injury accident at interstate freeway work zones in Ohio under various road conditions. the influence of adverse weather conditions as being responsible for the increase in work zone accidents. About 25% of the accidents occurred during the cloudy weather and 13% of the accidents occurred during rain. Figure 7 shows the distribution of fatal and injury accident at interstate freeway work zones in Ohio under various weather conditions Road-Dry Road-Wet Road-Snow Fig 6 Distribution of Road Condition and Injury Accidents (%) Straight-Level Straight-Grade Curve-Grade Curve-Level Road Condition Fig 7: Type of Road Contour Pavement Markings Construction Barricade No Controls Yield Sign and Injury Clear Cloudy Rain Snow Fig 6: Distribution of Weather Condition 7.6 Contributing Factors Based on the information provided on the accident reports, accident investigators attribute several contributing factors to fatal in work zones. As shown in Figure 9 these factors include Following Too Close, Failure to Control, and Improper Lane Change/Improper Passing. These three factors account for 71% of all fatal and injury at interstate freeways in Ohio work zones. 5% of fatal and injury are coded as having No Apparent Reason and 7% are identified as accidents that occurred due to driving at unsafe speed. Figure 9 shows the distribution of fatal and injury accident at interstate freeway work zones in Ohio under various Contributing Circumstances Followed Too Closely Failure to Control Improper Lane Change/Pa... Unsafe Speed Driver Inattention Operating Vehicle Erratically Fig 8: Type of Traffic Control Figure 5 According to Contributing Circumstances 7.5 Weather Condition About half of the fatal and injury at interstate freeways in Ohio occurred during clear weather, it rules out VIII. CONCLUSIONS The results of this study provide an insight on fatal and injury at different locations within work zones. 1646

6 Concentrating only on fatal and injury accidents allowed for evaluation of the predominant factors that are responsible for these. The activity area comes out to be the most dangerous area in a work zone and safety efforts must be concentrated on this area to improve the work zone safety. Predominance of rear-end at all locations within a work zone indicates that a measure cause of work zone is speed related. As discussed earlier, rear-end are mainly caused by vehicle driving at different speeds, resulting in a high speed variance. Any countermeasure that reduces the speed variance or causes drivers to drive at relatively same speed throughout the work zone will definitely improve the work zone safety. Also, to allow a more detailed analysis of within a work zone, the following fields should be added to the police crash report. The lane configuration of the work zone. The exact location of the crash within a work zone. Length of the work zone. Whether construction activities were going on at the time when crash occurred. Since the transition area of the work zones has a unique crash pattern featuring the significant increase of sideswipe same direction, a detailed study of this area should be conducted, particularly with respect to signing procedures that will encourage early merging of vehicles. 14. Summary Report on Work Zone Accidents. Standing Committee on Highway Traffic Safety, AASHTO, Washington, D.C., July Scheaffer, R.L., and McClave, J. T., Probability and Statistics for Engineers, 4 th Edition, Duxbury Press, Belmont, California. 16. Wackerly, D., Mendenhall III, W., and E. Schaffer, Mathematical Statistics with Applications, 5 th Edition, International Thompson Publishing Company, London, U.K., Guide for Selecting, Locating, and Designing Traffic Barriers, AASHTO, Washington, D.C. REFERENCES 1. Pigman, J.G., and Agent, K.R., 199. Highway accidents in construction and maintenance work zones. Transportation Research Record 127, Hall, J.W., and Lorenz, V.M., Characteristics of constructionzone accidents. Transportation Research Record 123, Pal, R. and Sinha, K.C., Analysis of crash rates at interstate work zones in Indiana. Transportation Research Record 1529, Bryden, J.E., Andrew, L.B., and Fortuniewicz, J.S., Work zone traffic accidents involving traffic control devices, safety features, and construction operations. Transportation Research Record 165, Ha, T.J., and Nemeth, Z.A., Detailed study of accident experience in construction and maintenance zones. Transportation Research Record 159, Garber, N.J., and Zhao, M., 22. Distribution and characteristics of at different work zone locations in Virginia. Transportation Research Record 1794, pp Bryden, J.E., Andrew, L.B., and Fortuniewicz, J.S., 2. Intrusion accidents on highway construction projects. Transportation Research Record 1715, Benekohal, R.F., Shim E. and Resende P.T.V., Truck drivers concerns in work zones: travel characteristics and accident experiences. Transportation Research Record 159, Wang, J., Hughes, F.M., and Paniati, J.F., Investigation of highway work zone : what we know and what we don t know. Transportation Research Record 1529, pp Bryden, J.E., Andrew, L.B., and Fortuniewicz, J.S., 2. Intrusion accidents on highway construction projects. Transportation Research Record 1715, pp Manual on Uniform Traffic Control Devices (MUTCD), 2. U.S. Dept. of Transportation, Federal Highway Administration. 12. Engineering Directive ED 99-2, Work zone intrusion countermeasures, New York State Department of Transportation (NYSDOT). 1647