By Keith Laing - 01/07/13 09:21 PM EST
The engines of cars traveling faster than that are typically loud enough to be heard, the DOT said.
Congress directed the transportation department to make the change in 2010 when it passed the Pedestrian Safety Enhancement Act.
National Highway and Traffic Safety Administrator (NHTSA) David Strickland said his agency took into consideration the cost to hybrid and electric automakers of implementing the new rules.
"Our proposal would allow manufacturers the flexibility to design different sounds for different makes and models while still providing an opportunity for pedestrians, bicyclists and the visually impaired to detect and recognize a vehicle and make a decision about whether it is safe to cross the street," Strickland said it statement.
NHTSA said the minimum sound requirements would prevent 2,800 pedestrian and bicycle injuries each year.