Development of a Partial Proportional Odds Model for Pedestrian Injury Severity at Intersections

  • Xi Lu China Academy of Transportation Science, MOT
  • Zhuanglin Ma Chang’an University, College of Transportation Engineering
  • Steven I-Jy Chien New Jersey Institute of Technology, Chang'an University
  • Ying Xiong Xi’an Traffic Information Center
Keywords: pedestrian, safety, crash injury severity, intersection, partial proportional odds model


Pedestrian injury in crashes at intersections often results from complex interaction among various factors. The factor identification is a critical task for understanding the causes and improving the pedestrian safety. A total of 2,614 crash records at signalized and non-signalized intersections were applied. A Partial Proportional Odds (PPO) model was developed to examine the factors influencing Pedestrian Injury Severity (PIS) because it can accommodate the ordered response nature of injury severity. An elasticity analysis was conducted to quantify the marginal effects of contributing factors on the likelihood of PIS. For signalized intersections, seven explanatory variables significantly affect the likelihood of PIS, in which five explanatory variables violate the Proportional Odds Assumption (POA). Local driver, truck, holiday, clear weather, and hit-and-run lead to higher likelihood of severer PIS. For non-signalized intersections, six explanatory variables were found significant to the PIS, in which three explanatory variables violate the POA. Young and adult drivers, senior pedestrian, bus/van, divided road, holiday, and darkness tend to increase the likelihood of severer PIS. The vehicles of large size and heavy weight (e.g. truck, bus/van) are significant factors to the PIS at both signalized and non-signalized intersections. The proposed PPO model has demonstrated its effectiveness in identifying the effects of contributing factors on the PIS.

Author Biographies

Xi Lu, China Academy of Transportation Science, MOT

Xi Lu is a research associate of China Academy of Transportation Science, MOT. He holds Ph.D. degree from the Institute of Technology of Technology (IIT) in US. His areas of expertise include urban transport policy, transportation planning, traffic safety, and mobility performance modeling.

Steven I-Jy Chien, New Jersey Institute of Technology, Chang'an University

Steven I-Jy Chien is a professor of John A. Reif, Jr. Department of Civil and Environmental Engineering, New Jersey Institute of Technology (NJIT). He is also a special term professor of S chool of Automobile, Chang’an University. He received his Ph.D. from the University of Maryland at College Park in US. Dr Chien’s current research activities and interests include: (1) travel time prediction in congested traffic networks, (2) mathematical and simulation modeling, (3) transportation system analysis, (4) intelligent transportation systems, (5) intermodal passenger transport, and (6) winter road maintenance planning and operation.

Ying Xiong, Xi’an Traffic Information Center

Ying Xiong is an engineer of Xi’an Traffic Information Center. She received her M.S. degree from Northwest University in China. Her primary research interest is Traffic Big Data Analysis.


National Highway Traffic Safety Administration. Fatality Analysis Reporting System (FARS) Encyclopedia. Washington, D.C.; 2018. Available from: [Accessed June 2018].

Ho G, Scialfa CT, Caird JK, Graw T. Visual search for traffic signs: The effects of clutter, luminance, and aging. Human Factors. 2001;43(2): 194-207.

Li Q, Qiao F, Wang X, Yu L. Drivers' smart advisory system improves driving performance at STOP sign intersections. Journal of Traffic and Transportation Engineering (English Edition). 2017;4(3): 262-271.

Oh C, Kang Y, Kim B, Kim W. Analysis of pedestrian-vehicle crashes in Korea: Focused on developing probabilistic pedestrian fatality model. Proceedings of the 84th Annual Meeting of the Transportation Research Board, Washington, D.C.; 2005.

Sarkar S, Richard T, Hunt J. Logistic regression model of risk of fatality in vehicle-pedestrian crashes on national highways in Bangladesh. Transportation Research Record. 2011;2264: 128-137.

Pour-Rouholamin M, Zhou H. Investigating the risk factors associated with pedestrian injury severity in Illinois. Journal of Safety Research. 2016;57: 9-17.

Ma Z, Lu X, Chien S-I, Hu D. Investigating factors influencing pedestrian injury severity at intersections. Traffic Injury Prevention. 2018;19(2): 159-164.

Tay R, Choi J, Kattan L, Khan A. A multinomial logit model of pedestrian-vehicle crash severity. International Journal of Sustainable Transportation. 2011;5(4): 233-249.

Pai C, Saleh W. Modeling motorcyclist injury severity by various crash types at T-junctions in the UK. Safety Science. 2008;46(8): 1234-1247.

Obeng K, Rokonuzzaman M. Pedestrian injury severity in automobile crashes. Journal of Safety Science and Technology. 2013;3: 9-17.

Zajac SS, Ivan JN. Factors influencing injury severity of motor vehicle-crossing pedestrian crashes in rural Connecticut. Accident Analysis and Prevention. 2003;35(3): 369-379.

Jang K, Park SH, Kang S, Song K-H, Kang S, Chung S. Evaluation of pedestrian safety: Pedestrian crash hot spots and risk factors for injury severity. Transportation Research Record. 2013;2393: 104-116.

Pei Y, Fu C. Investigating crash injury severity at unsignalized intersections in Heilongjiang Province, China. Journal of Traffic and Transportation Engineering (English Edition). 2014;1(4): 272-279.

Davis G. Relating severity of pedestrian injury to impact speed in vehicle-pedestrian crashes: Simple threshold model. Transportation Research Record. 2011;1773: 108-113.

Park S, Jang K, Park SH, Kim D-K, Chon KS. Analysis of injury severity in traffic crashes: A case study of Korean expressways. KSCE Journal of Civil Engineering. 2012;16(7): 1280-1288.

Peterson B, Harrel FE. Partial proportional odds models for ordinal response variables. Applied Statistics. 1990;39(2): 205-217.

Wang Z, Chen H, Lu J-J. Exploring impacts of factors contributing to injury severity at freeway diverge areas. Transportation Research Record. 2009;2102: 43-52.

Wang X, Jin Y, Sun H. Crash injury severity analysis at signalized intersections: Modeling techniques and significant factors. Proceedings of the 10th International Conference of Chinese Transportation Professionals, 4-8 August 2010, Beijing, China; 2010.

Zhao Y, Zhang S, Ma Z. Analysis of traffic accident severity on highway tunnels using the partial proportion odds model. China Journal of Highway Transportation. 2018;31(9): 159-166.

Liu P, Fan W. Analysis of head-on crash injury severity using a partial proportional odds model. Journal of Transportation Safety & Security. 2019. Available from: doi:10.1080/19439962.2019.1667933

Ma Z, Zhao W, Chien S-I, Dong C. Exploring factors contributing to crash injury severity on rural two-lane highways. Journal of Safety Research. 2015;55: 171-176.

Williams R. Generalized ordered logit/partial proportional odds models for ordinal dependent variables. The Stata Journal. 2006;6: 58-82.

Wooldridge JM. Econometric Analysis of Cross Section and Panel Data. Cambridge, Massachusetts: MIT Press; 2002.

Washington S, Karlaftis M, Mannering F. Statistical and Econometric Methods for Transportation Data Analysis. Boca Raton, FL: Chapman and Hall/CRC; 2003.

Roudsari B, Kaufman R, Koepsell T. Turning at intersections and pedestrian injuries. Traffic Injury Prevention. 2006;7(3): 283-289.

Kim JK, Ulfarsson GF, Shankar V, Kim S. Age and pedestrian injury severity in motor-vehicle crashes: A heteroskedastic logit analysis. Accident Analysis and Prevention. 2008;40(5): 1695-1702.

Kemel E. Wrong-way driving crashes on French divided roads. Accident Analysis and Prevention. 2015;75: 69-76.

Aidoo EN, Amoh-Gyimah R, Ackaah W. The effect of road and environmental characteristics on pedestrian hit-and-run accidents in Ghana. Accident Analysis and Prevention. 2013;53(1): 23-27.

Wang Y-Y, Haque MM, Chin HC, Goh YJ. Injury severity of pedestrian crashes in Singapore. Australasian Transport Research Forum 2013 Proceedings, 2-4 October 2013, Brisbane, Australia; 2013.

Olszewski P, Szagała P, Wolanski M, Zielinska A. Pedestrian fatality risk in accidents at unsignalized zebra crosswalks in Poland. Accident Analysis and Prevention. 2015;84: 83-91.

Christoforou Z, Cohen S, Karlaftis MG. Vehicle occupant injury severity on highways: An empirical investigation. Accident Analysis and Prevention. 2010;42(6): 1606-1620.

How to Cite
Lu X, Ma Z, Chien SI-J, Xiong Y. Development of a Partial Proportional Odds Model for Pedestrian Injury Severity at Intersections. PROMET [Internet]. 2020Jul.23 [cited 2020Aug.14];32(4):559-71. Available from: