Citation

Ruth R, Reust T. Collision 2008; 3(1): 44-47.

Copyright

(Copyright © 2008, Collision Publishing)

DOI

unavailable

PMID

unavailable

Abstract

Although the accuracy of precrash speed data has been assessed in some automotive event data recorders (EDR), to date no studies have evaluated the dynamic braking accuracy of precrash speed data in Ford Powertrain Control Modules (PCMs). The Ford PCM data is recorded in real time, reported more frequently and reported to a higher resolution than other EDRs. This paper evaluates the accuracy of speed data recorded in the Ford PCM during dynamic maximum antilock brake system (ABS) braking conditions. The authors drove a 2005 Ford Crown Victoria starting at 5 different initial speeds from 30 to 70 mph, making 6 runs at each speed, then braking as quickly as possible to a stop and turning the key off at the end of the run. The authors collected PCM EDR data after each run, which recorded the prior 25 seconds of speed and brake light switch on/off at 0.2 second intervals. The vehicle was also instrumented with a global positioning system- based Racelogic VBOX III that measured vehicle speed and brake light switch voltage at 100 times a second whenever it was activated. The PCM brake switch on/off signal was used to synchronize the data to the VBOX brake light voltage signal so the readings could be compared at the same points in time. The readings were compared and average and maximum differences were calculated. The findings show that the Ford PCM may underreport vehicle speed by up to a maximum of 8 mph during ABS braking at highway speeds. These results suggest that allowances for possible underreporting must be considered when estimating speed at impact from the last data point recorded prior to impact during APS braking.