The electric motor systems and direct-drive systems in EVs simply don't generate much of an audible sound at low speeds—other than a whine that varies by model from very subtle to almost.
Thanks to new legislation, and some agreements among automakers, the typical EV might not be making the sound of a vuvuzela or a Tie-Fighter, but you're going to hear it coming—perhaps with just a little more whine, wow and flutter.
Today President Obama signed the Pedestrian Safety Act (S. 841), which aims to help protect the blind and other pedestrians from "silent vehicle technology," as it was worded in a press release from the National Federation of the Blind.
The bill was introduced to the Senate last April but wasn't passed through Congress until last month.It might still be a while before the particulars of the bill are determined, as the bill calls for a study to be completed first, but it will almost certainly include stipulations that EVs make a particular noise when they're traveling at less than 20 mph. The new standard will apply to vehicles made or sold beginning two years after the issuance of the new standard.
So far, General Motors, early on in the development of its Chevrolet Volt, started working directly with the National Federation of the Blind, while Nissan has come up with several potential solutions and told GreenCarReports that such a sound is only needed up to about 12 mph; above that point tire noise is enough. Nissan presented its solution to NHTSA back in September 2009.
Not everyone is convinced that the 'Bell Bill' is useful, though, and some have pointed out that it unfairly singles out EVs, while high-end luxury cars that are especially quiet might be more dangerous—considering the distinctive high-pitched whine many EVs make when approaching.
There's also controversy over whether hybrids or electrics actually have a higher chance of hitting pedestrians. Several hybrid vehicles—like the Toyota Prius—run in a near-silent EV mode when coasting or cruising at low speeds, but with hundreds of thousands of hybrids on U.S. streets, there's no data set that conclusively shows an issue with hybrids, more than other types of vehicles, hitting pedestrians. That's even considering that hybrids are driven more in cities, and on low-speed streets congested with pedestrians.