Rules that will require plug-in electrified vehicles (PEVs) to emit certain sounds are being delayed.

The “quiet car” rules for hybrid and electric cars have been in the works since 2013 and aim to mandate audio alerts at low speeds for hybrids and electric vehicles, or any vehicle that operates at low speeds without an internal combustion engine running. According to a recent government filing, the quiet car rules will be delayed until at least mid-March with the National Highway Traffic Safety Administration (NHTSA) saying that “additional coordination is necessary.”

The rules were originally supposed to be finalized by January 2014 under a 2010 law passed by Congress, and gave automakers a minimum 18 months to comply once the rules were finalized.

NHTSA estimates that a hybrid vehicle is 19 percent more likely to be involved in a pedestrian crash compared with a traditional, gasoline-powered vehicle. The regulator believes if the proposal is implemented, there would be 2,800 fewer pedestrian and bicyclist injuries annually. Currently, around 125,000 pedestrians and bicyclists are injured annually.

Automakers have raised concerns about the sound alerts, noting that they are too loud and too complicated. The proposed rules would require automatic audio alerts for hybrid and electric vehicles traveling 18 miles per hour or slower.

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