Automated Vehicle Crash Sequences: Patterns and Potential Uses in Safety Testing

TL;DR

This study analyzes AV crash sequences from California reports to identify patterns and develop a scenario-based safety testing framework, enhancing understanding of crash dynamics and informing better testing protocols.

Contribution

It introduces a novel analysis of AV crash sequences and proposes a scenario-based testing framework incorporating sequence patterns for improved safety evaluation.

Findings

Most common crash pattern was collision after AV stop.

Disengagement often led to immediate collision with 68% transition probability.

Seven distinct crash sequence groups were identified with different dynamic features.

Abstract

With safety being one of the primary motivations for developing automated vehicles (AVs), extensive field and simulation tests are being carried out to ensure AVs can operate safely on roadways. Since 2014, the California DMV has been collecting AV collision and disengagement reports, which are valuable data sources for studying AV crash patterns. In this study, crash sequence data extracted from California AV collision reports were used to investigate patterns and how they may be used to develop AV test scenarios. Employing sequence analysis, this study evaluated 168 AV crashes (with AV in automatic driving mode before disengagement or collision) from 2015 to 2019. Analysis of subsequences showed that the most representative pattern in AV crashes was (collision following AV stop) type. Analysis of event transition showed that disengagement, as an event in 24 percent of all studied AV crash sequences, had a transition probability of 68 percent to an immediate collision. Cluster analysis characterized AV crash sequences into seven groups with distinctive crash dynamic features. Cross-tabulation analysis showed that sequence groups were significantly associated with variables measuring crash outcomes and describing environmental conditions. Crash sequences are useful for developing AV test scenarios. Based on the findings, a scenario-based AV safety testing framework was proposed with sequence of events embedded as a core component.