Effects of emergency escape ramps on crash injury severity reduction on mountain freeways: A case study in China

Abstract

Emergency escape ramps (EERs) is an infrastructure of mountain freeways to stop runaway vehicles. As the last defence of vehicle occupants’ safety, the performance of EERs in reducing crash injury severity is a concern for stakeholders of road safety. Based on crash records collected on a mountain freeway equipped with five EERs, this study compared the injury severity of crashes on EERs and other road sections, and identified the factors that significantly influence injury severity in the two conditions. Estimations of the parameter coefficients and marginal effects of a random parameters ordered probit model were used to infer EER performance under the impacts of various factors. The results confirm the effectiveness of EERs on the reduction of crash injury severity. The protection function of EERs is weakened by nighttime, the rollover status of crashed vehicle, multi-vehicle collisions, improper design or installation of the roadside infrastructure, drivers’ unfamiliarity with local driving conditions, and crashed vehicle weight. The paper compares the findings with those of previous studies and proposes some recommendations to improve EER performance for occupant and property protection on mountain freeways.

Keywords:

• Crash injury severity
• emergency escape ramp
• mountain freeways
• random parameters ordered probit model
• safety

Disclosure statement

No potential conflict of interest was reported by the authors.

Authors’ contribution

The authors confirm contribution to the paper as follows: study conception and design: Li Li, Guang-Ze Li, Dong Zhang; data collection: Wen-Chen Yang, Rui Fang, Li Li; analysis and interpretation of results: Li Li, Dong Zhang, Guang-Ze Li; draft manuscript preparation and revision: Li Li, Dong Zhang, Guang-Ze Li.

Data availability statement

Some data used in this study were provided by the two coauthors of this manuscript, Wen-Chen Yang and Rui Fang, who work at the National Engineering Laboratory for Surface Transportation Weather Impacts Prevention, Broadvision Engineering Consultants, Co.

Additional information

Funding

This research was funded by the Science and Technology Innovation Program of the Department of Transportation, Yunnan Province, China, under Grant No. 2018303; the National Natural Science Foundation of China under Grant No. 71901040, and 71701031; the General Program of Natural Science Foundation, Yunnan Province, China, under Grant No. 2019FB072; the Key Research and Development Programs of Shaanxi Province, under Grant No. 2018ZDCXL-GY-05-04, 2019ZDLGY15-04-02; and the Fundamental Research Funds for the Central Universities under Grant CHD 300102321101, 300102210525.