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Quiet (Hybrid) Vehicles – The Requirements of Sound Added to Quiet Vehicles

October 8, 2013


People who are blind, deafblind, or partially sighted rely on the sound produced by running vehicles to interpret traffic patterns and travel safely throughout their communities. Vehicles that do not produce a sufficient amount of sound can be significantly harder to detect and thus pose a safety concern for pedestrians who are blind, deafblind, or partially sighted. The United Nations is involved in the development of a global technical standard concerning the addition of sound to quiet vehicles. This position statement expresses recommendations regarding the requirements of adding sound to quiet vehicles. These recommendations echo those put forward in a position statement produced by the World Blind Union in February 2013.


Over the last decade, quiet vehicles – including hybrid and electric cars – have become more commonplace as a result of their reduced impact on the environment and their increased mileage. This has led to a growing concern among organizations representing people who are blind, deafblind, or partially sighted. For those who rely heavily on the sound produced by vehicles in order to travel safely, as do people with vision loss, quiet vehicles present a serious risk of injury or death. Children, cyclists, and inattentive walkers are also at risk.

Research has demonstrated that quiet vehicles are harder to detect by people who are blind, deafblind, or partially sighted.[1] In order to ensure that pedestrians who use vehicle noise to travel safely are not put at unnecessary risk, quiet vehicles must meet a minimum sound standard. A working group of the United Nations has been tasked with developing a global technical regulation that will set out the criteria for meeting a minimum sound standard.

The organizations listed below have endorsed the following recommendations that are aimed at expressing a consumer perspective on the questions being considered by the UN working group.


  1. A minimum standard that attempts to strike a balance between a low noise that is dangerous for pedestrians and a loud sound that disturbs people must make safety the highest priority.
  2. Any sound added to a quiet vehicle must be similar in character to the sound emitted by an internal combustion engine.
  3. A sound added to a quiet vehicle must be emitted whenever the vehicle is in operation, including when stopped.
  4. A minimum sound standard must apply to any quiet vehicle including electric, hybrid electric and quiet internal combustion engines.
  5. A minimum sound standard must prohibit the inclusion of a driver controlled on/off switch.

Supporting Organizations


[1] See, for example, Pliskow, J., Naghshineh, K., Wall Emerson, R., Kim, D. et al. (2011). Detection of Hybrid and Quiet Vehicles by Blind and Visually Impaired Pedestrians. SAE Technical Paper.