415 – Modeling in Transportation Safety Issues
Reducing Accelerometer Data from Instrumented Vehicles
Michael O. Bishop
University of Iowa College of Public Health
Jeffrey D. Dawson
University of Iowa College of Public Health
Jennifer Merickel
University of Nebraska Medical Center
Matthew Rizzo
University of Nebraska Medical Center
In on-road behavior studies, vehicle acceleration is sampled at high frequencies and then reduced to meaningful metrics over short driving segments. We examined road test data from 65 subjects driving over a common route, as well as driving in naturalistic situations using their own vehicle. We isolated 24-second segments, then reduced the accelerometer data via two methods: 1) standard deviation (SD) within a segment, and 2) re-centering parameter from a time-series model previously developed for driving simulator data. We analyzed the data via random effects models to ascertain the intraclass correlations (ICC's) of the metrics. With and without adjusting for speed, the ICC of SD within a segment tended to be much greater than the ICC of the re-centering parameter for the segment (range: 0-30% vs. 0-1%). Also, the ICC's from the naturalistic driving data tended to be much greater than the fixed route data (range: 0-30% vs. 0-9%), which could reflect individuals exhibiting their more usual driving behavior in naturalistic environments. Findings illustrate the difficulty of identifying meaningful driving metrics and compare these across different epochs, road segments and research platforms.