Potential Factors Affecting Roadway Departure Crashes in Oahu, Hawaii Pasha Hashemi (1), Adrian Ricardo Archilla(2) (1)Graduate Research Assistant, Department of Civil and Environmental Engineering, University of Hawaii at Manoa (2) Associate Professor, Department of Civil and Environmental Engineering, University of Hawaii at Manoa
Outline 2/ 26
What is A Roadway Departure Crash? The FHWA defines a RwD crash as: A nonintersection crash in which a vehicle crosses an edge line, a centerline, or otherwise leaves the traveled way. Overturn Opposed Direction Collison with Fixed objects 3/ 26
Why RwD crashes are important? According to the Federal Highway Administration (FHWA),roadway departure (RwD) crashes account for approximately 56% of highway fatalities in the United States, and 54% in Hawaii. U.S Hawaii 4/ 26
General Safety Improvement Process Identify the contributing factors Developing Safety performance functions (SPF) Using Crash Modification Factors for simulate effect of countermeasures Calculating the improvement 5/ 26
General Safety Improvement Process Identify the contributing factors Developing Safety performance functions (SPF) Using Crash Modification Factors for simulate effect of countermeasures Calculating the improvement 6/ 26
RwD Crashes Lord et al., investigated the relationship between single vehicle run off the road crashes and the geometric characteristics of rural two lane roads Crash frequency and severity will increase when there is a decrease in lateral clearance or shoulder width Liu et al., using data pertaining only to fatal single-vehicle ROR crashes Identified: The roadway, driver, environment, and vehicle-related factors associated with fatal singlevehicle ROR crashes Kim et al., the interplay between demographic, land use, roadway accessibility variables and types of crashes demographic variables such as job count and number of people living below the poverty level are significantly associated with injury crashes and pedestrian and bike crashes 7/ 26
No study was found on RwD crashes in Hawaii as well as considering the role of roadway design, human, and environmental factors. Less information was found in the literature about RwD crashes & identifying common circumstances in which RwD crashes occur. 1-Spatial distribution of RwD crashes and contributing factors(roadway design, human factor, environment) 2-Compare the most common circumstances of RwD crashes versus most probable circumstances 8/ 26
The State of Hawaii motor vehicle accident reports (2008-2011) Crash State of Hawaii office of planning and the Honolulu land information systems websites to obtain various GIS shapefiles The Honolulu police districts map and related land use information were obtained from the Honolulu police department 9/ 26
Map of Oahu 10/ 26
Bayesian Statistical Approach The approach of Bayesian statistics is used to recognize the predominance of crash-related factors such as roadway design, human and environmental factors in probability of occurrence RwD crashes = ( ) ( ) = h h = h h = h = h 11/ 26
Crash Statistics in Oahu, Hawaii Total number of Crashes Total Number of Fatalities Total Number of Incapacitating Injuries 12/ 26
Spatial Distribution Total number of All Crashes 13/ 26 Total number of RwD Crashes
Spatial Distribution of RwD Crashes Divided by All Crashes Total number of Crashes Total Number of Fatalities Total Number of Incapacitating Injuries 14/ 26
Roadway Departure Crashes, Fatalities and Injuries by Locality Crashes Fatalities Injuries Locality Total Percentage Total Percentage Total Percentage CountyRoad 2412 51.68% 26 32.10% 1402 43.64% Rural 158 3.39% 8 9.88% 131 4.08% Urban 2254 48.30% 18 22.22% 1271 39.56% State Road 2255 48.32% 55 67.90% 1811 56.36% Rural 413 8.85% 8 9.88% 316 9.84% Urban 1842 39.47% 47 58.02% 1495 46.53% Grand Total 4667 100.00% 81 100.00% 3213 100.00% 15/ 26
Distribution of RwD Crash by Type in Oahu, Hawaii RwD Crash Type Fixed object Head on Overturn /Rollover Ran off the road-right Ra n off the road-left Side Swipe Ground Total District 1 57% 3% 1% 31% 2% 7% 100% District 2 55% 5% 3% 21% 7% 10% 100% District 3 65% 5% 3% 21% 1% 5% 100% District 4 58% 5% 3% 21% 6% 8% 100% District 5 64% 2% 2% 25% 2% 6% 100% District 6 46% 1% 0% 40% 2% 10% 100% District 7 54% 4% 1% 31% 2% 8% 100% District 8 60% 4% 5% 21% 2% 9% 100% 16/ 26
Distribution of RwD Crash by traffic way description in Oahu Traffic-way Description Tota l Number of Percentage Fatalities Percentage RwD Cra shes 2-way, Undivided 2005 44.66% 31 39.74% 2-way, Divided, Median barrier 947 21.10% 22 28.21% 2-Way Undivided with Left Turn Lane 638 14.21% 12 15.38% 1-Way Trafficway 756 16.84% 8 10.26% 2-way, Divided, Unprotected Median 26 0.58% 3 3.85% Other 117 2.61% 2 2.56% Grand Total 4489 100.00% 78 100.00% 17/ 26
Distribution of Geometric Design Categorizes in RwD Crash Vertical Alignment Horizontal Alignment 18/ 26
Distribution of Road Surface Categorizes in RwD Crash Roadway Surface Composition Roadway Surface Condition 19/ 26
Human Factors 1200 1000 Total Number of RwD Accidents 800 600 400 200 0 Human Factor Total Number of RwD Crashes Categorized by Human Factors Distribution of Main Human Factors in RwD Crash Occurrence 20/ 26
600 Environmental Factors 400 500 Total Numebr of RwD Crashes 400 300 Total Number of RwD Crashes 350 300 250 200 150 200 100 100 50 0 1 2 3 4 5 6 7 8 District Clear Cloudy Rain Other Weather Daylight 0 Spot illumination 1 2 3 4 5 6 7 8 District Continuous Lighting Other(Dawn,Dusk,Dark) Light 21/ 26
Bayesian Statistical Analysis Table 6 Probability of Occurrence RwD crashes if classified crash class i (Roadway Design factor) Trafficway 2-way, 2-way, Divided, 2-Way Undivided with 1-Way 2-way, Divided, Description Undivided Median barrier Left Turn Lane Trafficway Unprotected Median 25.64% 22.87% 24.35% 26.08% 9.42% Vertical Alignment Level Hillcrest Uphill Downhill Sag 16.77% 24.61% 28.16% 29.08% 33.78% Roadway Surface Dry Wet Mud Debris Oil Water Sand 17.90% 29.72% 35.71% 33.33% 70.00% 26.67% 33.33% Roadway Composite Concrete Asphalt Gravel Dirt Human Factor 23.93% 19.02% 44.44% 53.17% Probability of Occurrence RwD crashes if classified crash class i (Human Factor) Inattention Misjudgment Fatigue Alcohol Illegal Drugs Illness Legal Meds. Emotional Physical Impaired 13.24% 19.19% 57.75% 42.21% 47.50% 47.52% 50.00% 38.24% 39.34% Probability of Occurrence RwD crashes if classified crash class i (Environmental Factor) Weather Condition Clear Cloudy Rain Hazy Windy Blowing Sand 21.76% 26.50% 36.26% 30.68% 27.10% 23.08% Lighting Condition Daylight Dawn Dusk Spot Continuous Dark Dark/No Dark/Unkno illumination Lighting light wn 17.02% 31.08% 25.50% 35.43% 32.22% 34.85% 50.98% 32.82% 22/ 26
While RwD crashes are more frequent in following circumstance: straight roads with no grade, and dried asphalt surface, driver`s misjudgments as a human facto, clear weather with light But they are more probable in these circumstance: Dark or no light condition 2-way undivided roads Curvy roads Hazy weather Most probable RwD crash occurrence Hilly roads Fatigue Oily road surfaces Dirt as a surface composition 23/ 26
1. Federal Highway Administration. Roadway Departure (RwD) Strategic Plan. http://safety.fhwa.dot.gov/roadway_dept/. 2. Neuman, T. R., R. Pfefer, K. L. Slack, K. K. Hardy, F. Council, H. McGee, L. Prothe, and K. Eccles. A guide for addressing run-off-road collisions. Guidance for Implementation of AAHSTO Strategic Highway Safety PUn. Washington, DC: TRB, 2003. 3. Neuman, T. R., R. Pfefer, K. L. Slack, K. K. Hardy, H. McGee, L. Prothe, K. Eccles, and F. Council. GUIDANCE FOR IMPLEMENTATION OF THE AASHTO STRATEGIC HIGHWAY SAFETY PLAN. VOLUME 4: A GUIDE FOR ADDRESSING HEAD-ON COLLISIONS. 2003. 4. Hauer, E., D. Harwood, F. Council, and M. Griffith. Estimating safety by the empirical Bayes method: a tutorial. Transportation Research Record: Journal of the Transportation Research Board, No. 1784, 2002, pp. 126 131. 5. Peng, Y., S. R. Geedipally, and D. Lord. Investigating the Effect of Roadside features on Single-Vehicle Roadway Departure Crashes on Rural Two-Lane Roads 2. 2012. 6. Liu, C., and R. Subramanian. Factors related to fatal single-vehicle run-off-road crashes. 2009. 7. Almutairi, O. E. Characteristics of Injury and Fatality of Run-Off-Road Crashes on Ohio Roadways. 8. Kim, K., and L. Nitz. Spatial Analysis of Honolulu Motor Vehicle Crashes: I. Spatial Patterns. 1995. 9. Kim, K., P. Pant, and E. Yamashita. Accidents and accessibility: Measuring influences of demographic and land use variables in Honolulu, Hawaii. Transportation Research Record: Journal of the Transportation Research Board, No. 2147, 2010, pp. 9 17. 24/ 26
Acknowledgement Disclaimer The contents of this presentation reflect the views of the authors, who are responsible for the facts and accuracy of the facts presented herein. The contents do not necessarily reflect the official views or policies of the State of Hawaii, Department of Transportation or the Federal Highway Administration. 25/ 26
Thank You! Questions? hashemi@hawaii.edu 26/ 26