Relationship of Vertical Illuminance to Pedestrian Visibility in Crosswalks

Abstract

Twenty-six participants evaluated a series of crosswalk lighting designs by visually detecting objects at each crosswalk location while traveling in a moving vehicle. The research was performed on a closed test track under nighttime conditions while the participants were driving an SUV with regular halogen headlamps. The conditions included several vertical illuminance levels (6, 10, 20, and 30 lux), varied luminaire types [high-pressure sodium (HPS) and metal halide (MH)], and various target object types (pedestrian and surrogate objects). Only one age group of participants (66 years and older) was used for the study, with equal representation of males and females. The participants were asked to detect objects at each crosswalk location when they were confident an object was present. The results indicated that object detection distances changed on the basis of vertical illuminance level, luminaire type, and object type. Object detection distance for HPS was greatest at 30 vertical lux and for MH at 20 vertical lux. However, these results were moderated by the clothing color of the target object. When object color was considered, 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 than black-clothed objects, especially at the 20-lux lighting level. The results suggest that a vertical illuminance level of 20 lux at crosswalk locations provides adequate levels for target object detection. In addition to benefiting from vertical illuminance, target objects that wore white clothing had detection distances superior to other object types of different clothing colors. Recommendations for crosswalk lighting configurations are further discussed.

Role of Expectancy, Motion and Overhead Lighting on Nighttime Visibility

“…From the results of this study motion seems to draw more attention than expectancy when it comes to detecting new objects at nighttime on roadways. The results of this study reinforce the safety benefits of overhead lighting (Edwards & Gibbons, 2008;Polus & Katz, 1978;Wanvik, 2009) and decrease in visual performance of older drivers (Owens, Wood, & Owens, 2007;Wood, Tyrrell, & Carberry, 2005). Finally, the results also confirm existing research that drivers tend to detect human form (static or moving) with relative ease when compared to other inanimate objects (Balk, et al, 2008;Johansson, 1973;Owens, et al, 1994).…”

“…Overhead lighting also increases the distance at which pedestrians are detected (Bhagavathula, et al, 2012;Edwards & Gibbons, 2008). Presence of overhead lighting not only decreases the risk of pedestrian accidents (Wanvik, 2009), but also reduces the number of nighttime pedestrian crashes (Pegrum, 1972;Polus & Katz, 1978).…”

Road Lighting

“…By analysing the number of missed and incorrect detections and the response time to correct detections, it was found that 20 lx additional vertical illuminance was required for satisfactory results. This value was confirmed in a dynamic test with a similar group of elderly persons (Edwards and Gibbons 2008). Of course, the additional vertical illuminance is more effective if the installation supplying it is such that an increase of horizontal lighting level is limited as much as possible.…”

Road lighting research for drivers and pedestrians: The basis of luminance and illuminance recommendations

“…186 US guidance 4 suggests instead to use vertical illuminances (at 1.5 m height), these being 10 lux and 2 lux for areas of high and medium pedestrian conflict, these data as determined from test track studies. 187 A limitation of specifying a single value of illuminance is that it does not account for local conditions: it may be too low if visual adaptation is raised by extraneous local lighting or by a generally high level of road lighting. In the UK, TR12 of the Institution of Lighting Professionals overcomes this by recommending an illuminance relative to that of the road in which the crossing is placed, which is itself chosen partly with consideration to the surrounding environment.…”

“…186 US guidance 4 suggests instead to use vertical illuminances (at 1.5 m height), these being 10 lux and 2 lux for areas of high and medium pedestrian conflict, these data as determined from test track studies. 187…”