The Assessment of New Roadway Lighting in Rain and Fog


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National Surface Transportation Safety Center for Excellence


This study sought to determine if different types of roadway lighting performed differently in rain or fog. The performance of the lighting was determined by participants’ ability to detect different objects along the shoulder of the road as they drove an experimental vehicle through simulated rain and fog at night on the Virginia Smart Roads Highway. Twenty-seven participants took part in this study, which consisted of three sessions: one for consenting and screening, one for performing the study in clear weather, and one for performing the study in rain and fog conditions.. As participants drove along the Smart Roads Highway, they looked for and verbally identified two types of objects that appeared on the right shoulder of the road. These included pedestrians wearing red, blue, or gray clothing, or small 7-inch square wooden targets painted red, blue, or gray. Participants also identified the color of the object. Participants performed these tasks under three different types of roadway lighting: traditional high-pressure sodium (HPS) lamps and two types of light-emitting diode (LED) lamps with different color temperatures (3500K and 6000K). Presentation orders of the lights and objects were counter-balanced to reduce learning effects. The performance of each light was determined by the distance at which participants could identify objects (detection distance) and the distance at which they could recognize the color of the objects (recognition distance). For each object and weather condition, a 2 (age) × 3 (lighting) × 3 (color) analysis of variance (ANOVA) was conducted with an alpha of 0.05. No significant difference was found among light types on participants’ ability to detect pedestrians in any weather condition. Results showed that all three light types performed equally for the detection of pedestrians in all weather conditions and for the detection of targets in clear and fog conditions. A significant difference was only found for the detection of targets in rain. However, there was no clear best performer as each light type performed well for the detection of some colors of targets and poorly for others. On average, detection distances for targets in the rain were approximately 10 m longer under the LED lights compared to the HPS.



transportation safety, Lighting