Although bicyclists riding during dark conditions are generally required to have appropriate lighting on their vehicles or persons, requirements vary from state to state and many bicyclists do not comply with the requirements. Good illumination also helps nighttime bicyclists see surface conditions and obstacles or people in the path of travel. Data from five years of North Carolina bicycle-motor vehicle crashes indicate that about one quarter of reported collisions and more than half of bicyclist fatalities occurred during non-daylight conditions, probably far exceeding the proportion of riding that occurs under these conditions.⁶ Similarly, estimates referred to by Florida State University⁷ indicate that "nearly 60 percent of all adult fatal bicycle accidents in Florida occur during twilight and night hours even though less than 3 percent of bicycle riding takes place during that time period." Bicyclists, particularly commuters, may have to ride during early dawn hours or be caught by twilight, particularly in the winter months.

Improved roadway lighting may help to reduce crashes that occur under less than optimal light conditions. Intersections may warrant higher lighting levels than roadway segments. Good lighting on roadways, bridges, tunnels and shared-use paths is also important for personal security. Lighting improvements are typically thought of as an urban and suburban treatment, but there may be situations where lighting improvements are appropriate in rural locations. Examples of such locations might include rural roadways that serve as bicycling connectors between outlying or neighboring population areas and urban centers, and intersections or shared-use trail crossings used by significant numbers of cyclists. More research is needed on the safety and mobility benefits of lighting improvements to bicyclists and pedestrians. The American Association of State Highway and Transportation Officials³ guide recommends using average maintained illumination levels of between 5 and 22 lux, and the Florida DOT recommends 25 as the average initial lux for shared-use paths, 16 for bike facilities on arterial roads, and 11 for all other roadways.⁸ The Wisconsin Bicycle Facility Design Handbook also provides guidance for path illumination (p. 4–35 to 4–37).⁹ Other roadway lighting resources include American National Standard Practice for Roadway Lighting ANSI IESNA (RP-8-00) and other publications (available from the Illuminating Engineering Society) and AASHTO’s 1984 An Informational Guide for Roadway Lighting (update anticipated). A forthcoming NCHRP project will develop guidelines for roadway lighting based on safety benefits and costs.

Lighting is a complex treatment requiring thoughtful analysis. Not only are there safety and security issues for bicyclists, pedestrians and motorists, but potential light pollution, long-term energy costs, and aesthetics also are factors. With good design, lighting can enhance safety of the bicycling (as well as pedestrian) environment and improve the ambience of areas of nighttime activity.