Do Drivers Respond to Lead Vehicles Gradually or Suddenly?

Abstract

The aim of the current study was to determine whether drivers’ responses to stopped and slow-moving lead vehicles transition gradually in phases, each associated with a distinct optical expansion rate. We also examined whether results were affected by a cell phone conversation and expectancy. We used a driving simulator to assess six response inputs of (1) begins to release the accelerator, (2) releases accelerator completely, (3) starts to press brake (4) comfort-level braking (5) unanticipated-level braking and (6) brake pedal pressed more than 90 percent. Optical expansion rate differed among the first four inputs (the fifth and sixth did not occur enough to analyze), meaning drivers respond to lead vehicles in phases. When drivers were not engaged in a cell phone conversation, optical expansion rate for the perceptual event preceding unanticipated braking was greater when the lead vehicle was stopped compared to slowed. Expectancy did not affect optical expansion rates.