Evaluation of audible traffic signals for pedestrians with visual impairment

Abstract

Audible signals are used at several road intersections across Canada to enable pedestrians with visual impairment to cross safely. The acoustic parameters can be quite different among the different signals used and this can be the source of particular difficulties for the users. A study was conducted to identify which signal is the easiest to localize, among 6 signals proposed, and which one is judged the safest. Two of the signals (cuckoo and peep-peep) are standardized by the Transportation Association of Canada, and the remaining signals are four variations of the melody signal proposed by the Institut Nazareth et Louis-Braille (Longueuil, QC). A group of 10 subjects with normal vision and 10 subjects with visual impairment participated. Objective sound localization measurements were made outside on a quiet street using a rotating chair as angular pointer. A questionnaire was also administered to obtain an individual appraisal of the 6 signals, and a rating system allowed judging the signals relative to each other. The results for the melody signals varied substantially with the fundamental frequency and harmonic richness of the musical sequence. Two of the melodies, with the lowest fundamental frequency and richest harmonic content, emerged as the best signals overall. Among the standardised signals, the cuckoo provided acceptable performance, but the peep-peep should be abandoned because of very poor subjective assessment.