They are designed to simplify the driving experience: Push a button rather than turn a key.
But recent fatalities, including this past weekend in Boca Raton, Fla., in which drivers left the car running and died of carbon monoxide poisoning, have highlighted whether keyless-ignition cars are safe.
Adele and Mort Victor were found dead in their bedroom. Their keyless-ignition car has now been impounded by police.
Mary Rivera of Long Island, N.Y., escaped with her life after leaving her Toyota running in her garage in 2009 but her husband died of carbon monoxide poisoning.
"The ignition didn't turn off," Rivera said. "I was very familiar with the car. I drove it every day. I don't know. I thought I turned it off but apparently I didn't."
She was saved by her brother, John, who was worried when he didn't hear from her. "I thought she was dead. I rushed to her and was yelling at her and shaking her to have some response," John Rivera said.
More than 160 car models now offer keyless start.
Toyota said its cars sound a warning when the driver leaves without shutting down the car.
Still, the Center for Auto Safety said it tracked six fatalities involving push-button starters and wants car manufacturers to return to keys.
When asked whether drivers are partly to blame for walking out of the car without turning off the ignition, Clarence Ditlow, executive director with the Center for Auto Safety, said it's part of the problem.
"Sure, it's our fault," Ditlow said. "But this is a device that makes it easy to forget, and the cost of forgetfulness should not be death by carbon monoxide."
The National Highway Traffic Safety Administration wants manufacturers to standardize all the push-button starters to avoid confusion.
In the meantime, Mary Rivera and several other push-button start users are suing the manufacturers for alleged losses.
Rivera said manufacturers are "a 100 percent at blame because they designed something that could be left on without a person knowing. So we have to blame them 100 percent."