Acoustic traffic signal for blind pedestrians

Abstract The development of an acoustic traffic signal for blind pedestrians is described. The WALK and WAIT signals used represent a compromise between many contradictory demands, e.g. easy localisation and detection in a background of traffic noise, minimum annoyance, maximum attenuation into dwellings and simple and reliable construction. The WALK sound consists of 200 ms pulses at a repetition rate of 2·5 Hz. The WAIT sound consists of 400 ms pulses at a repetition rate of 0·5 Hz. Both WALK and WAIT pulses are formed from an 880 Hz sawtooth or square wave signal. A weak attention signal is audible (automatic level control) within a distance of 2–3 m from the traffic light pole. The system has been in use for more than 2 years. Twenty-six blind pedestrians tested the system and found it very useful. A questionnaire investigation showed no adverse reactions from neighbours to the system. The attention system is being standardised in Denmark. The system is prepared for extension with a louder guiding signal which guides the blind across the crossing.