Errors in judging the approach rate of motorcycles in nighttime conditions and the effect of an improved lighting configuration

  • Published: Accident Analysis and Prevention, 45 (2012) 432-437
  • 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 explore drivers’ abilities to make judgments of motorcycles and car approach speeds in night time driving conditions, when only the headlights are visible, as well as the effectiveness of a tri-headlight configuration on the accuracy of motorcycle speed judgments.


A sample of 13 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 appropriate car stimulus was used as a reference vehicle in all trials, travelling towards the observation point at a fixed speed of 30 mph (13.4 m/s).

Key Findings:

  • Individuals were significantly more accurate at judging the speed of two car headlights compared with the standard solo headlight motorcycle. However, the inclusion of a tri-headlight formation on a standard motorcycle frame significantly improved these judgments.

  • A further investigation demonstrated that tri-headlight configurations with separation between headlights on the horizontal and vertical axes are most effective for yielding accurate speed judgments.


Perception, vision, looming, tau, motorcycle, conspicuity


As noted by the authors, “The extent to which observers struggle to accurately judge motorcycle speed based on a solo headlight in night time conditions is rather alarming.”