It was something that had never occurred to Jane Flannigan, until she got the call Sunday that her eight-year-old son had been hit by a car while biking with a friend.

Owen Erickson was not badly hurt, though he did end up on the hood of the car.

But when the car’s driver moved his Toyota Prius from the street to the curb, Flannigan noticed something.

“I saw the car, but I could not hear anything,” she recalled about the hybrid vehicle which was operating on battery power at the time. “It is totally silent,” she said.

That’s when it dawned on Flannigan, Owen never heard the Prius before he cut in front of it. “Bikers, runners, anybody out on the street, I think it’s a huge safety issue,” she said.

She’s not the only one.

Last month legislation was introduced in the U.S. House of Representative that could eventually require hybrids to emit a minimum amount of noise.

It’s a priority piece of legislation for the National Federation of the Blind, which believes Hybrids pose a real threat to those who rely on noise from cars to keep themselves safe.

“These quiet cars that are very difficult to hear in the normal flow of everyday outdoor activity play a safety hazard,” says Jennifer Dunnam, president of the NFB’s Minnesota affiliate. “Blind people depend on their hearing to know what the traffic is doing.”

Toyota has not taken a position on the legislation, but is aware of the concerns behind it.

“We do have to step back and take a look,” said John Hanson, Toyota’s national manager of environmental, safety and quality communications.

The Prius ranks third among Toyota models in sales, behind Camry and Corolla, according the Hanson.

Flannigan doesn’t blame the driver of the Prius for running into her son, since Owen biked out in front of his car but she does cut her son some slack.

“We’re conditioned to hear car noises,” she says. “This is a big safety issue.”