Night-time driving visibility associated with LED streetlight dimming

Area of Science:

• Road safety
• Human factors in transportation
• Lighting engineering

Background:

• LED streetlighting and dimming are increasingly adopted globally for cost savings.
• The impact of streetlight dimming on driver performance and safety remains under-investigated.
• Existing research primarily focuses on the economic benefits of LED dimming.

Purpose of the Study:

• To investigate the effects of LED streetlight dimming on night-time driving performance.
• To quantify the impact of varying dimming levels on driver reaction times and object recognition.
• To provide data for establishing safe dimming levels for road networks.

Main Methods:

• 14 licensed drivers participated in a night-time driving study on a closed circuit.
• An instrumented vehicle was used to record driving performance under different streetlight dimming levels (25%, 50%, 75%, 100%).
• Tasks included measuring reaction times and recognition distances for a moving target and a pedestrian.

Main Results:

• Streetlight dimming significantly delayed driver reaction times to a moving target (0.4s delay at 25% light).
• Pedestrian recognition distances were significantly shorter under dimmed conditions (15m shorter at 25% light).
• Reduced light output led to an estimated 6m reduction in recognition distance for moving targets.

Conclusions:

• Streetlight dimming negatively impacts driver visibility and reaction times during night driving.
• The observed reductions in recognition distances and increased reaction times suggest potential safety concerns.
• Further research is needed to determine safe dimming levels for streetlighting to ensure road safety.