Developing safety performance functions for freeways at different aggregation levels using multi-state microscopic traffic detector data

Jinghui Yuan; Mohamed Abdel-Aty; Jingwan Fu; Yina Wu; Lishengsa Yue; Naveen Eluru

doi:10.1016/j.aap.2021.105984

Developing safety performance functions for freeways at different aggregation levels using multi-state microscopic traffic detector data

Accid Anal Prev. 2021 Mar:151:105984. doi: 10.1016/j.aap.2021.105984. Epub 2021 Jan 20.

Authors

Jinghui Yuan¹, Mohamed Abdel-Aty², Jingwan Fu², Yina Wu², Lishengsa Yue², Naveen Eluru²

Affiliations

¹ Department of Civil, Environmental & Construction Engineering, University of Central Florida, Orlando, FL 32816, USA. Electronic address: jinghuiyuan@knights.ucf.edu.
² Department of Civil, Environmental & Construction Engineering, University of Central Florida, Orlando, FL 32816, USA.

PMID: 33484973
DOI: 10.1016/j.aap.2021.105984

Abstract

Safety Performance Functions (SPFs) have been widely used by researchers and practitioners to conduct roadway safety evaluation. Traditional SPFs are usually developed by using annual average daily traffic (AADT) along with geometric characteristics. However, the high level of aggregation may lead to a failure to capture the temporal variation in traffic characteristics (e.g., traffic volume and speed) and crash frequencies. In this study, SPFs at different aggregation levels were developed based on microscopic traffic detector data from California, Florida, and Virginia. More specifically, five aggregation levels were considered: (1) annual average weekday hourly traffic (AAWDHT), (2) annual average weekend hourly traffic (AAWEHT), (3) annual average weekday peak/off-peak traffic (AAWDPT), (4) annual average day of the week traffic (AADOWT), and (5) annual average daily traffic (AADT). Model estimation results showed that the segment length and volume, as exposure variables, are significant across all the aggregation levels. Average speed is significant with a negative coefficient, and the standard deviation of speed was found to be positively associated with the crash frequency. It is noteworthy that the operation of the high occupancy vehicle (HOV) lanes was found to have a positive effect on crash frequency across all the aggregation levels. The model results also showed that the AAWDPT and AADOWT models consistently performed better (the improvements range from 3.14%-16.20%) than the AADT-based SPF, which implies that the differences between the day of the week and peak/off-peak periods should be considered in the development of crash prediction models. The model transferability results indicated that the SPFs between Florida and Virginia are transferrable, while the models between California and the other two states are not transferrable.

Keywords: Aggregation level; Freeway; High occupancy vehicle lane; Microscopic traffic detector data; Safety performance function.

MeSH terms

Accidents, Traffic* / prevention & control
Environment Design
Florida
Humans
Models, Statistical*
Safety
Virginia