WASHINGTON — Electric cars, which have soundless engines, would need to make noise to let pedestrians know they are near under a proposed federal rule released Monday.
Sounds would need to be audible when vehicles are traveling slower than 18 miles per hour so that electric and hybrid-electric cars could be heard by bicyclists and pedestrians, particularly the visually impaired.
The National Highway Traffic Safety Administration proposed the so-called quiet-car rule. It says the measure would save 35 lives over each model year of hybrid vehicles and prevent about 2,800 injuries.
‘‘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,’’ the agency’s administrator, David Strickland, said in a statement.
Adding external speakers to quiet vehicles would cost about $25 million a year, or about $35 per light vehicle, the agency said. About $1.48 million of the annual costs would be to equip large trucks and buses and motorcycles with sound.
A study says quiet cars are twice as likely as vehicles with internal-combustion engines to crash into pedestrians.
That cost compares with $2.7 billion a year for a rule the group failed to issue by its deadline last week to require backup cameras in all new cars. Both rules are required by laws passed by Congress.
The National Federation of the Blind has pushed for the rule, saying an increasing number of cars that don’t make noise at low speeds put blind people at risk.
Above 18 miles per hour, cars make enough noise, the agency said. Hybrid-electric cars use electric engines at low speeds and can switch to internal-combustion engines. Fully electric cars such as the Nissan Leaf use only battery power.
Cars that are not using internal-combustion engines don’t make noise while they accelerate or idle like vehicles that are powered by gasoline or diesel fuel. The Pedestrian Safety Enhancement Act of 2010 requires a rule addressing this issue by Jan. 4, 2014.
Quiet cars are twice as likely as vehicles with internal-combustion engines to be involved in pedestrian crashes when backing up, slowing or stopping, starting in traffic, or entering or leaving a parking space, a 2011 study said.