Determining an Improved Traffic Conflict Indicator for Highway Safety Estimation Based on Vehicle Trajectory Data

Ruoxi Jiang,Hongguang Chang,Naikan Ding,Jingan Wu,Bing Liu,Ji Qiu,Shunying Zhu

doi:10.3390/su13169278

Ruoxi Jiang, Hongguang Chang + Show 5 more

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https://doi.org/10.3390/su13169278

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Abstract

Currently, several traffic conflict indicators are used as surrogate safety measures. Each indicator has its own advantages, limitations, and suitability. There are only a few studies focusing on fixed object conflicts of highway safety estimation using traffic conflict technique. This study investigated which conflict indicator was more suitable for traffic safety estimation based on conflict-accident Pearson correlation analysis. First, a high-altitude unmanned aerial vehicle was used to collect multiple continuous high-precision videos of the Jinan-Qingdao highway. The vehicle trajectory data outputted from recognition of the videos were used to acquire conflict data following the procedure for each conflict indicator. Then, an improved indicator Ti was proposed based on the advantages and limitations of the conventional indicators. This indicator contained definitions and calculation for three types of traffic conflicts (rear-end, lane change and with fixed object). Then the conflict-accident correlation analysis of TTC (Time to Collision)/PET (Post Encroachment Time)/DRAC (Deceleration Rate to Avoid Crash)/Ti indicators were carried out. The results show that the average value of the correlation coefficient for each indicator with different thresholds are 0.670 for TTC, 0.669 for PET, and 0.710 for DRAC, and 0.771 for Ti, which Ti indicator is obviously higher than the other three conventional indicators. The findings of this study suggest TTC often fails to identify lane change conflicts, PET indicator easily misjudges some rear-end conflict when the speed of the following vehicle is slower than the leading vehicle, and PET is less informative than other indicators. At the same time, these conventional indicators do not consider the vehicle-fixed objects conflicts. The improved Ti can overcome these shortcomings; thus, Ti has the highest correlation. More data are needed to verify and support the study.

Highlights

Traffic conflict indicators are used as surrogate safety measures to assess the severity of every traffic conflict
Indicator between the serious is used as the traffic conflict indicator, and correlation conflict TTC
For threshold values ranging from 1 s to 10 s, above, and the highest correlation occurs when the threshold value is 1 s. This phenomethe correlation decreases with increase in the threshold value, stabilizes at 4 s and above, non shows that the reliability of identifying the risk of traffic conflicts is low when the and the highest correlation occurs when the threshold value is 1 s

Summary

Introduction

Traffic conflict indicators are used as surrogate safety measures to assess the severity of every traffic conflict. The third measures characteristics of the vehicle’s own movement, such as deceleration. The most common indicator of the vehicle’s own movement characteristics is the deceleration rate to avoid crash (DRAC) [5,6,7]. In recent years, some studies have begun to use combined indicators for conflict identification [8,9,10,11].

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