01557382

Component

Surrogate safety analysis is the practice of diagnosing road safety by observation of ordinary traffic behaviour instead of rare traffic accidents. While this proactive approach was first proposed in the 60’s, issues of subjectivity, transferability, and validity impeded the technique’s maturity. However, it has recently gained some renewed traction with the advent of sophisticated, large-scale, microscopic data acquisition techniques solving some of the issues of objectivity, though the tasks of improving model transferability and validity remain, with the exception of speed indicators, which benefit from a large body of evidence linking them to road safety, especially collision severity. While trajectory measurement techniques have improved, the interpretation and definition of dangerous traffic events still lags. Various competing safety indicators have been proposed and tried, some more precise, objective, or context-sensitive than others.bThis paper examines and reviews the definition and interpretations of time-to-collision, one of the most ubiquitous and least context-specific surrogate safety indicators, for its suitability as an indicator of dangerous traffic events. An important emphasis is put on motion prediction methodology when defining time-to-collision, as well as aggregation methods of instantaneous time-to-collision exposure. This analysis is performed using one of the largest trajectory data sets collected to date for the purpose of surrogate safety analysis. The study recommends the aggregation of instantaneous time-to-collision indicators by 15th percentile over the use of minimum values, highlights the context-dependency of constant velocity motion prediction (particularly regarding car-following), recommends the use of motion pattern prediction using trajectory learning, and examines sensitivity to traffic event ranking by collision probability threshold.

This paper was sponsored by TRB committee ANB20 Safety Data, Analysis and Evaluation.

01550057

15-4629

English

20p

2015

Transportation Research Board 94th Annual Meeting

Digital/other

Figures; References; Tables

Crash exposure; Crashes; Highway safety; Mathematical prediction; Traffic crashes

Surrogate safety measures; Time to collision

Highways; Safety and Human Factors; I80: Accident Studies

Transportation Research Board Annual Meeting 2015 Paper #15-4629

TRIS, TRB, ATRI

Dec 30 2014 1:32PM