To determine how distracted and normal driving differ, this report re-examines driving performance data from the advanced collision avoidance system (ACAS) field operational test (FOT), a naturalistic driving study (96 drivers, 136,792 miles). In terms of overall driving performance statistics, distraction (defined as 4 successive video frames where the driver’s head was not oriented to the forward scene) had almost no effect, except for decreasing mean throttle opening by 36% and mean speed by 6%. No consistent normal/distracted differences were found in the parameters that fit the distributions of steering wheel angle, heading, and speed (all double exponential) and throttle opening (gamma) for each road type by driver age combination. In contrast, logistic regression identified other statistics and factors that discriminated between normal and distracted driving. They included (a) turn signal use and age group for expressways, (b) gender and if the lead vehicle range exceeded 60 m for major roads, and (c) lane width, lane offset, and lead vehicle velocity for minor roads. Finally, in a supplemental analysis, throttle holds (1 - 4 s periods of essentially no throttle change suggesting the driver may not be attending to driving) were actually more common for normal driving when a single time window (1 s) by threshold change combination (4 %) was selected. However, when settings (time windows of 1 – 4 s, thresholds of 1 – 4 %) were tailored for each age group by road class combination, throttle holds could identify when the driver was distracted. (Author/publisher)
Abstract