The Wall Street Journal reported in February 2007 on concerns that quiet cars like the Prius may pose a safety risk to those who rely on engine noise to sense the presence or location of moving vehicles.[79] Blind pedestrians are a primary concern, and the National Federation of the Blind advocates audio emitters on hybrid vehicles,[80] but increased risks may also affect sighted pedestrians or bicyclists who are accustomed to aural cues from vehicles. In July 2007, a spokesperson for Toyota said the company is aware of the issue and is studying options[81].

The UK engineering group Lotus is developing a device for fitment to hybrid and electric cars, designed to eliminate the problem caused to pedestrians and cyclists when are running silently. The device will emit a simulated engine-like noise, controlled by the vehicle speed, from a front-mounted speaker. The device has been installed on a Prius, and is triggered only when the car is running in electric-only mode.[82]

The National Highway Traffic Safety Administration (NHTSA) held a hearing June 23, 2008 on this issue and the submitted materials are available www.regulations.gov - search NHTSA-2008-0108-0020 for opposition research and report. This includes the Dr. Christopher Hogan analysis of the available NHTSA pedestrian accident data showing: (1) the Prius has the same rate as ordinary cars; (2) no blind has been killed by a Prius, yet, and; (3) an average of 5 blind are part of the annual 4,700 pedestrian deaths each year. This hearing relates to pending Federal legislation HR 5734 and applies to the nearly identical California legislation SB 1174.