Illuminance required to detect a pavement obstacle of critical size

Abstract

This paper investigates the illuminance needed to detect trip hazards for pedestrians walking after dark. In previous work, it was assumed that the critical obstacle height is 25 mm: further review of accident data and foot clearance data suggests instead that 10 mm is the critical height. Eye tracking records suggest a tendency for obstacles to be detected approximately 3.4 m ahead. Interpretation of obstacle detection data suggests horizontal photopic illuminances of up to 0.9 lux are required for peripheral detection of a 10 mm obstacle 3.4 m ahead, according to the scotopic/photopic ratio of the lighting and the age of the observer.

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

“…157 Further work sought to identify the critical height obstacle that pedestrians ought to be able to detect, rejecting the widely cited (and apparently unsubstantiated) rule of 25 mm, and instead suggesting 10 mm to be the critical height. 158 In all, 10 mm is the approximate lower quartile of the range of minimum foot clearance when walking along a flat surface and the lower limit of the range of heights associated with the most frequent number of tripping accident compensation claims.…”

Hazard Detection: Testing the Caveats of Previous Studies

“…Further increase in illuminance brings negligible improvement in detection performance. The critical hazard was defined as a 10 mm variation in vertical height, much smaller than the previously assumed 25 mm threshold, and this was determined using data regarding foot clearance and injuries (Fotios and Uttley, 2018). However, the experiments were conducted using simplified situations which raise questions of the extent to which the results can be safely generalised to wider situations.…”

Assessing Public Perceptions about Road Lighting in Five Neighborhoods of Tirana, Albania

“…There were fifteen road (exterior) lighting assessment questionnaires in total. A road lighting assessment questionnaire was composed of sixteen questions that was prepared (by the author) to assess the perceived safety [11], pavement obstacle detection [3], visibility and road lighting related perceived satisfaction by public. Road lighting assessment questionnaires were filled in immediately after the sunset following the day-dark approach [12], [13].…”

“…The distance (2 m, 5 m, 10 m) also related to the luminance and distance effects for a familiar face detection and a face expression detection and a pavement obstacle detection. For example, eye tracking records proposed 'a tendency for obstacles to be detected approximately 3.4 m ahead' with a horizontal (photopic) illuminances of 0.90 lux[3]. Yang and Fotios[2] suggested the luminance from above 1.0 cd/m 2 for a facial identification at a distance of 10 m, and the luminance of 1.0 cd/m 2 for a facial expression with a probability of 50 percent of a correct identification at a distance of 15 m.…”