Judgments of approach speed for motorcycles across different lighting levels and the effect of an improved tri-headlight configuration

  • Published: Accident Analysis and Prevention, 48 (2012) 341-345
  • Authors: Gould M, Poulter D R, Helman S and Wann J P
  • Date Added: 25 Jan 2014
  • Last Update: 25 Jan 2014
  • Format: html


To investigate drivers’ judgments of motorcycle and car approach speeds across a number of levels of luminance within a virtual city scene, as well as the effectiveness of a tri-headlight formation on motorcycle speed judgments.


A sample of 14 participants was subjected to visual stimuli. The stimuli were presented on a 34 cm × 27 cm Cathode Ray Tube monitor display (1024 × 768 pixels). In this instance, participants were asked to indicate which of two visual stimuli presented sequentially was travelling at the fastest speed. The vehicle stimuli were presented in a virtual urban city environment and travelled along the road surface towards the observation point. The ambient light levels were adjusted within the virtual scene to simulate five different daylight conditions (daylight, lower daylight, dusk, early evening and night).

Key Findings:

  • The study examined how accurately individuals are able to judge the speed of motorcycles and cars across a number of different ambient light level conditions. The results demonstrate that the accuracy of individuals’ judgments remained constant across all lighting levels for the car stimulus. However, participant estimations of the solo headlight motorcycle speed became significantly less accurate in the degraded lighting levels of the early night and night-time conditions.

  • Increasing motorcycle headlight separation is one way of maintaining the visible width of the vehicle as night falls, and the addition of the tri-headlight formation considerably reduced the degradation in speed judgments under lower light conditions in this experiment.


Perception, vision, looming, tau, motorcycle, conspicuity