Pre-impact braking in crashes: insights from event data recorders (EDRs)

Abstract

This study examined start-of-braking times from event data recorder (EDR) data of 170 bullet (through-vehicle/striking) vehicles involved in crashes in South Australia over the period 2017 to 2020. A formula for calculating the start-of-braking time to an accuracy of 0.05-second time points was derived and applied to the EDR data from the bullet vehicles. A third of bullet vehicle drivers did not apply the brakes before impact, and almost three quarters of bullet vehicle drivers had a start-of-braking time of less than or equal to one second. The average start-of-braking time was 0.87 seconds. Start-of-braking times were found to vary between crash types. No right-angle type crashes had start-of-braking times of greater than 1.5 seconds, with the vast majority of drivers in these types of crashes having a braking time of less than 1 second. In contrast, single vehicle crashes had a wide range of start-of-braking times. Of the common crash types, hit parked vehicle crashes had the highest percentage of drivers that did not brake at all (73%), while right-turn – opposite crashes had the lowest (12%). High speed zones had higher start-of-braking times than low speed zones. A general limitation of this study is that it did not include data from near crashes. This could be rectified in a future study by combining EDR data from crashes with naturalistic driving data from near crashes.