Influence of Vertical Illuminance on Pedestrian Visibility in Crosswalks

This project investigated the lighting levels required for crosswalk illumination. The current European methods for lighting suggest a crosswalk lighting level of 40 vertical lux for ensured safety. Two major questions were studied: the required vertical illuminance level for adequate pedestrian visibility and the selection of an object that could act as a surrogate for the pedestrian. The vertical illuminance was determined from an experiment that measured the visibility of pedestrians at lighting levels of 5, 20, 40, and 60 vertical lux. During the experiment, a crosswalk scene was presented to the participants and the time taken for identification of an object was measured. In addition to the lighting level, the conditions used in the experiment were lamp type (metal halide versus high-pressure sodium), the presence of glare, the use of overhead lighting, and the type of pedestrian clothing (white, black, and denim). The study found that a lighting design level of 20 vertical lux is likely adequate for proper pedestrian visibility. Except in selected cases, the lamp type was not significant. The impact of glare was not influenced by the lighting design. Three surrogate objects were developed for the experiment and were tested in the same manner as the pedestrians. The surrogates used were an extruded octagon, a cylinder, and a cylinder with a ball on top. These surrogates were selected to allow easy lighting design calculations while best representing a pedestrian. The experiment found that all surrogates performed equally well and that the surrogate can be chosen on the basis of the ease of calculation. It is recommended that a cylinder be used as a pedestrian surrogate.