Keyless ignition allows drivers to start their cars with the press of a button while an electronic key fob remains in their pocket or purse.
Keyless ignition systems - widely used in cars around the world - consist of a device that is carried by the driver, allowing them to start the vehicle with the press of a button linked to the fob.
Keyless cars have a unsafe downside.
The New York Times reported Sunday that at least 20 deaths have been linked to carbon monoxide poisoning caused by cars left idling in garages when their drivers thought their engines were off. Sometimes, drivers mistakenly believe their cars are off after parking them, which can result in carbon monoxide filling their garages and homes.
In 2011, the National Traffic Safety Administration (NHTSA) proposed regulation for warning systems in keyless vehicles.
While automakers have installed warning systems into their keyless-ignition vehicles voluntarily, there is no universal standard among the systems.
The New York Times arrived at its number from news reports, lawsuits, and police and fire records tracked by advocacy groups.
Some auto manufacturers are incorporating measures like alarms to warn drivers or have the vehicle turn off automatically if it's standing idle for a while, but not all cars have these features.