The Influence of Vertical Illuminance on Pedestrian Visibility in Crosswalk
Source: 18th Biennial Transportation Research Board Visibility Symposium
"Twenty-six participants evaluated a series of crosswalk lighting designs by visually detecting objects within each crosswalk location. The research was performed on a closed test track under nighttime conditions while driving a Sport Utility Vehicle (SUV) with regular halogen headlamps. The conditions presented to each participant included varying illuminance levels (6, 10, 20, and 30 lux), varied luminaires (High Pressure Sodium [HPS], Metal Halide [MH]) and different object types (pedestrian and surrogate objects). The participant was asked to detect objects within each crosswalk location when they were confident there was an object present. The presentation of objects was varied to diminish expectation effects. The results indicated that object detection distances varied based on illuminance level, luminaire type, and object type. Object detection distance for the HPS was greatest at 30 lux and for MH at 20 lux. However, these results were moderated based on clothing color of the object. When object color was taken into consideration, pedestrians in white clothing were identified earlier under the HPS lighting condition at 20 lux. Under the MH configuration, denim-clothed objects were detected earlier compared to black-clothed objects, especially at a 20 lux lighting level. The results indicate crosswalk lighting levels provide adequate object lighting at 20 lux. Furthermore, pedestrians dressed in white clothing have superior detection distances compared to other object types."
