In 2008, NCHRP Report 624: Selection and Application of Warning Lights on Roadway Operations Equipment presented guidelines for selection and application of warning lights to improve the conspicuity and recognizability of roadway operations equipment used for construction, maintenance, utility work, and other similar activities. To accomplish this objective, the researchers conducted a review of current practices for use of warning lights on maintenance vehicles and an investigation to evaluate several aspects of the warning light system. This investigation included photometric characterization, screening, and performance experiments to evaluate lighting parameters that influence system performance as defined in terms of glare and vehicle detectability.
This research project enhances NCHRP Report 624 and does not replace it. Since NCHRP Report 624 was completed, significant technology changes and pressure from increased speeds, traffic volumes, and distracted drivers necessitate additional guidelines to include: (1) the significant improvements made to light emitting diodes (LED) electronics and optics, which are replacing previous lighting technology; (2) on-road vehicle and off-road equipment configurations; (3) an evaluation and recommendation(s) for vehicle base color or combination of color; (4) minimum and maximum lighting configurations, using Class 1 lights (lighting; color and combination of colors, lens color; flash pattern, flash rate, and light synchronization; light synchronization between multiple vehicles; light placement; and light size and type); (5) combination of lighting systems with dissimilar characteristics; (6) minimum and maximum conspicuity configurations (pattern, colors, retro reflectivity sheeting type, and location and size); (7) urban and rural environments; (8) day, night, dusk, dawn, snow, rain, fog and other weather effects on lighting and marking recommendations; (9) rear, side, and front approaches to vehicles taking into consideration horizontal and vertical curves and oblique approaches; (10) interrelated effects of vehicle color, light color, combination of lighting systems, flash rate, and markings; and (11) effects of warning lights on traffic signs and message boards (in particular portable message boards), especially with older drivers.
The objective of this research is to update and enhance previous guidelines addressed in NCHRP Report 624. The research project will include on-road vehicle and off-road equipment configurations. This research will identify configurations and provide a tool that describes the interrelated effects of vehicle color, light color, combination of lighting systems, flash rate, and markings, with maximum and minimum limits, to make highway vehicles and equipment quickly and easily recognizable. This research project will build on the existing research done on warning lights, reflective sheeting, and base color with the intention to provide an all-embracing guideline for DOT vehicles. Results of this project will allow motorists the opportunity to better perceive hazards with highway maintenance and construction operations, reducing crash rates, and increasing safety.