Field Evaluation of Locomotive Conspicuity Lights

Devoe, Donald B.; Abernethy, C. N. · 1975 · ROSA P / United States. Federal Railroad Administration

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Summary

This 1975 report by the U.S. Department of Transportation’s Transportation Systems Center evaluates the effectiveness of flashing xenon strobe lights mounted on locomotives to alert motorists at railroad-highway grade crossings. The study was motivated by the fact that, as of 1972, only 22% of public grade crossings had active protection, leaving nearly 175,000 public and 140,000 private crossings reliant on passive signs or no warning. Instrumenting trains rather than crossings was identified as a cost-effective alternative, given the disparity in numbers between locomotives and crossings. The research aimed to determine if strobe lights could enhance train conspicuity without causing adverse side effects for drivers or railroad crews. The methodology combined a comprehensive literature review with field evaluations and controlled experiments. Three locomotives from the Bangor and Aroostook Railroad were equipped with xenon strobe lights and operated in regular revenue service. Researchers conducted programmed observations of the lights under various conditions (daylight, sunset, night) from distances up to one-half mile and interviewed fourteen train crew members. Additionally, a laboratory experiment assessed whether the strobes interfered with the perception of adjacent trackside signals, while a field experiment recorded the reactions of automobile drivers who unexpectedly encountered the strobes while approaching grade crossings. The literature review established design criteria for eight parameters, including light type, flash frequency, duration, arrangement, usage, beam size, brightness, and color, balancing attention-getting capability against potential distraction or physiological harm. The findings confirmed that flashing xenon strobe lights effectively attract motorist attention to approaching locomotives. Crucially, the study found that these lights produced no uncontrollable adverse side effects. Specifically, the strobes did not interfere with the perception of trackside signals, nor did they disrupt normal operations for motorists or locomotive crews. The short duration of the xenon flashes (approximately 1 millisecond) was determined to have minimal impact on dark adaptation, avoiding the severe disruption caused by longer-duration lights. Subjective ratings from previous studies cited in the review also favored strobes for night-time visibility. Based on these results, the report recommends the use of high-intensity, short-duration flash tubes to increase locomotive conspicuity. Specific operational guidelines include engineer-controlled activation, with intensity set at 800 candelas at night and 4,000 candelas during the day. The authors recommend masking the rear thirty degrees of the strobe beam to prevent distraction and suggest further studies to evaluate crew exposure to backscatter in fog or snow and to compare strobes with alternative lighting systems. The report supports the technical recommendation for more extensive research tests of strobe lights in railroad operational service.

Key finding

Flashing xenon strobe lights mounted on locomotives attract attention to the locomotive and produce no uncontrollable adverse side effects.

Methodology

mixed_methods

Sample size: 14

Provenance

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Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.

Topics

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• emergency work zone conspicuity
• vehicle conspicuity
• motorcycle conspicuity
• rail grade crossings
• visibility analysis litigation
• roadway lighting effects