Are hybrid cars too quiet for their own good?

Jana Littrell certainly thinks so. Littrell, who is blind, was walking through a bank parking lot in the East Bay town of Albany a year ago when her foot was run over by a Toyota Prius backing out of a parking space. She wasn’t injured and the driver apologized effusively, she recalled. But the experience shook her up.

“It has definitely put me more on my guard,” said Littrell, who teaches Braille to newly blind adults. “But I don’t know how much good that’s going to do me if I can’t hear the car coming.”

Concerns are growing that quiet-running hybrids such as the Prius pose a hazard to pedestrians, especially the 1.3 million Americans who are legally blind. The problem occurs when the cars are running at very low speeds on electric power, making about as much noise as a golf cart.

“There’s this silent-but-deadly zone where we cannot hear these cars,” said Bryan Bashin, a Sacramento management consultant. “We’re not just worried about blind people. It’s a hazard to pets, joggers, young children, cyclists, people who have their back turned. . . .”

Federal traffic safety regulators report that no deaths or serious injuries have been attributed to quiet-running hybrids. But an ongoing study at UC Riverside has produced some of the first scientific evidence that hybrids may pose a hazard to pedestrians, according to preliminary results to be released today.

Meanwhile, the issue is drawing attention from the auto industry, state lawmakers and federal regulators. It even spawned at least one Silicon Valley start-up that’s trying to develop an audible pedestrian warning system for hybrids.

Bashin, who is sightless, is working with the National Federation of the Blind to push legislation that could eventually require installation of “noise emitting” devices on hybrids and other vehicles that run at least part of the time on electric power.

That prospect doesn’t sit well with some car owners. The message board at greenhybrid.com, a website for hybrid enthusiasts, has seen lively debates over the issue. In one recent post, a Toyota Camry hybrid owner wrote that “the world around us is getting louder and along come hybrids and WHAM! They get blasted by a group claiming they are too quiet.”

The debate comes as hybrids are becoming increasingly common. More than 350,000 were sold in the U.S. last year, according to marketing information firm J.D. Power and Associates.

Prius owner Sarah Forth of Silver Lake knows the issue from both sides.

“I noticed the cars creeping up on me when I was walking around,” Forth recalled. “After I got one, I put two and two together and realized, ‘I’m a road hazard in this car.’ ”

The vehicles are powered by a combination of gasoline and electricity and are prized for their fuel economy. They’re particularly popular in California, which buys almost half the hybrids sold in the U.S. by Toyota Motor Corp., the leading hybrid maker.

And coming soon: cars powered only by electricity that produce very little engine noise at any speed (although, as with hybrids, air flow and tire noise would become noticeable above 20 or 25 miles per hour).

Currently, most of the concern is directed at the top-selling Prius and vehicles such as the Camry that use similar gasoline-electric engines. The Honda Civic, the No. 4-selling hybrid in America, is noisier because it employs a system that almost never switches into electric-only mode.

The UC Riverside study has found that test subjects had to be 40% closer to silent-running hybrids than to cars with traditional gasoline engines before they could hear them.

“Our preliminary findings could mean that there is an added danger with hybrid cars, particularly at intersections and parking lots,” said Lawrence Rosenblum, a psychology professor doing the study.

Toyota engineers are looking for a solution, but have yet to come up with one.

“Vehicle safety and pedestrian safety are at the top of our list,” spokesman Bill Kwong said. “At this point, we’re trying to balance the needs of sight-impaired people with other sociological concerns such as noise pollution.”

One problem has been in isolating exactly what sounds most people associate with an approaching vehicle, such as the engine revving, the fan belt, tire noise or other sounds. Artificial warning cues “like chirping or chimes are not identified by test subjects as a vehicle at all,” the automaker said.

Interim solutions include training guide dogs for the blind to detect cars by sight as well as sound. Training schools such as Guide Dogs for the Blind in San Rafael and Guide Dogs of the Desert near Palm Springs have added Priuses to their training regimens partly in response to concerns about hybrid cars.

Longer term, the National Highway Traffic Safety Administration has promised to launch a wide-ranging investigation into the issue and several states are considering legislation. A bill soon to be headed to the governor of Maryland would create a task force to conduct a study and recommend solutions.

A group of Stanford University students has formed a company -- Santa Clara-based Enhanced Vehicle Acoustics -- that is developing an after-market product for Toyota hybrids that goes beyond simply making a noise to alert nearby pedestrians. For example, by linking to the vehicle’s computer, the system would be able to direct its sounds to the right or left to warn pedestrians that the car is about to make a turn.

Bashin and other advocates for the blind are sympathetic to complaints from hybrid fans. But, he asked, “what am I supposed to do, stay home?”

martin.zimmerman@ latimes.com