The role of ambient light level in fatal crashes: inferences from daylight saving time transitions

  • Published: Accident Analysis and Prevention Volume 34, pp.487–498, 2001
  • Authors: J. M. Sullivan and M. J. Flannagan
  • Date Added: 18 Mar 2013
  • Last Update: 18 Mar 2013
  • Format: pdf


The purpose of this study was to estimate the size of the influence of ambient light level on fatal pedestrian and vehicle RTIs in three scenarios. The scenarios were:

  • fatal pedestrian RTIs at intersections,
  • fatal pedestrian RTIs on dark rural roads, and
  • fatal single-vehicle run-off-road RTIs on dark, curved roads.


Each scenario’s sensitivity to light level was evaluated by comparing the number of fatal RTIs across changes to and from daylight saving time, within daily time periods in which an abrupt change in light level occurs relative to official clock time. The analyses included 11 years of fatal RTIs in the United States, between 1987 and 1997.

Key Findings:

  • Scenarios involving pedestrians were most sensitive to light level, some cases showing up to seven times more risk at night over daytime.

  • In contrast, single-vehicle run-off-road RTIs showed little difference between light and dark time periods, suggesting factors other than light level play the dominant role in these RTIs.

  • These results are discussed in the context of the possible safety improvements offered by new developments in adaptive vehicle headlighting.


Pedestrians, Daylight savings, Fatalities


No reference to SDST but useful facts about risks to pedestrians.