The concern that very quiet hybrid and electric cars may pose a danger to unaware pedestrians has been around for a decade or more now.
Back in 2010, Congress required the National Highway Traffic Safety Administration to develop rules for adding alert noises to cars running on silent electric power.
The law was adopted at the urging of the National Federation for the Blind, among other groups.
But those rules, due back in January, aren't ready. So automakers have stepped forward to urge a delay in the schedule that requires them to start phasing in the devices for 2016.
According to The Detroit News, a pair of auto-industry lobbying groups – the Alliance of Automobile Manufacturers and Association of Global Automakers – jointly issued a letter urging NHTSA to postpone full compliance until September 1, 2018.
That's because not only are the rules due on January 4 lagging, but "it is apparent that there remains a great deal of uncertainty as to the content of the final requirements," according to the groups.
The NHTSA had proposed rules in January 2013 that the groups said then would "result in alert sounds that are louder than necessary, create driver and occupant annoyance and cost more than necessary.”
The agency suggested that hybrid and electric cars running only on electricity should produce a sound at speeds up to 18.6 mph. It even published a list of possible sounds at different volumes.
As usual, automakers claim that the costs of compliance estimated by the Federal agency – $35 per car to add a noise generator and a speaker system – are far too low. The real figure could be five times that number, say the lobbying groups.
Various electric cars already on the market – including the Nissan Leaf, the highest-selling battery electric vehicle in the US – already have an alert noise built in. In the Leaf's case, it's a sort of chirping sound.
The Chevrolet Volt range-extended electric car has a driver-actuated alert noise, triggered by pulling back on the indicator stalk.
It's not clear that there's substantial data supporting the need for such noise-making devices, although a preliminary study in 2009 appeared to indicate that hybrids had a higher rate of pedestrian and cyclist collisions than non-hybrids.