When should cyclists use their bike headlights most effectively?

Cyclists should use their bike headlights most effectively from twilight to dawn because this is when visibility is significantly reduced, making it harder for both cyclists and motorists to see one another. During these times, light is dim or absent, which increases the risk of accidents. By using headlights during twilight and dawn, cyclists can enhance their visibility to drivers and make their presence known on the road.

Additionally, this timeframe follows legal requirements in many places, which typically mandate the use of headlights during low-light conditions. While it is also important for cyclists to use headlights during poor weather, daylight hours, and when riding in groups, the critical nature of low-light conditions makes the period from twilight to dawn the most essential time for utilizing bike headlights effectively.