Effect of Impact-Triggered Automatic Braking in Multiple Impact Crashes

This study proposes an impact-triggered automatic braking system as a potential safety improvement based on the characteristics of the Multiple Impact Crashes (MICs). The system activates with a signal of airbag deployment in a collision to reduce the vehicle speed in the subsequent collisions. The effectiveness was estimated by an in-depth review of the National Automotive Sampling System-Crashworthiness Data System (NASS-CDS). The cases were extracted on the basis of the 3-point lap and shoulder belted occupants, incurring Maximum Abbreviated Injury Scale level 3 to 6 injuries (MAIS 3+), in the crashes occurred from 2004 to 2006, without vehicle rollover or occupant ejection, where the involved vehicles were 2000 and newer model year cars and light trucks. They were classified into three categories: (a) Single Impact Crash (SIC), (b) Multiple Impact Crash in which the Severest Impact Event occurred at the 1st collision (MIC-SIE 1) and (c) Multiple Impact Crash in which the Severest Impact Event occurred at or after the 2nd Impact Event (MIC-SIE 2+). Among the MIC-SIE 2+, we focused on the cases where at least one airbag was deployed before the severest impact event. Then we selected the cases where the vehicle traveled more than 10m without any damage to the chassis between the location of the airbag deployment event and the severest impact event. Among the 13,068 crashes (SIC and MIC), the proposed braking system could be activated in 640 crashes and effective in 509 crashes per year (weighted) to avoid the subsequent collisions or to mitigate the impact severity in the subsequent collisions. To verify the effectiveness, a driving test was performed with a prototype car to reproduce a typical scenario of MIC-SIE2+. The test showed that the proposed automatic braking reduced the braking distance by 36% compared to manual braking.