Analysis of car-to-bicycle approach patterns for developing active safety devices

ABSTRACT

Objective: To reduce the severity of injuries and the number of cyclist deaths in traffic accidents, active safety devices providing cyclist detection are considered to be effective countermeasures. The features of car-to-bicycle collisions need to be known in detail to develop such safety devices.

Methods: The study investigated near-miss situations captured by drive recorders installed in passenger cars. Because similarities in the approach patterns between near-miss incidents and real-world fatal cyclist accidents in Japan were confirmed, we analyzed the 229 near-miss incident data via video capturing bicycles crossing the road in front of forward-moving cars. Using a video frame captured by a drive recorder, the time to collision (TTC) was calculated from the car's velocity and the distance between the car and bicycle at the moment when the bicycle initially appeared.

Results: The average TTC in the cases where bicycles emerged from behind obstructions was shorter than that in the cases where drivers had unobstructed views of the bicycles. In comparing the TTC of car-to-bicycle near-miss incidents to the previously obtained results of car-to-pedestrian near-miss incidents, it was determined that the average TTC in car-to-bicycle near-miss incidents was significantly longer than that in car-to-pedestrian near-miss incidents.

Conclusions: When considering the TTC in the test protocol of evaluation for safety performance of active safety devices, we propose individual TTCs for evaluation of cyclist and pedestrian detections, respectively. In the test protocols, the following 2 scenarios should be employed: bicycle emerging from behind an unobstructed view and bicycle emerging from behind obstructions.

KEYWORDS:

• car-to-bicycle approach
• near-miss incident
• fatal accident
• time to collision
• prevention

Acknowledgments

The authors thank Katsumi Moro, formerly at the Society of Automotive Engineers of Japan and currently with the Tokyo University of Agriculture and Technology; Kunio Takahashi of the National Traffic Safety and Environment Laboratory Japan; and Professor Tsutomu Doi of Ibaraki Christian University for their cooperation with analysis of near-miss data.

Table 3a. Comparison of TTC for vulnerable road user types.

Table 3b. Comparison of distance for vulnerable road user types.

Table 3c. Comparison of car velocity for vulnerable road user types.

Funding

This study was funded by Grants-in-Aid for Scientific Research, Japan, from 2013 to 2016 under the project title “Clarification of Behavior and Biomechanics of Cyclist in Traffic Accidents.”