WASHINGTON -- Mirrors have been a fixture of the automobile since the first Indianapolis 500, in 1911, when the engineer Ray Harroun outfitted his single-seat Marmon Wasp race car with a rearview mirror.
Rivals complained. They called Harroun reckless, saying he would put them in danger if he didn't use the same visibility aid as the rest of the field: a mechanic who rode shotgun and watched the rear.
Harroun ultimately won permission to use the mirror. Then he won the race. Soon, the riding mechanic was obsolete.
A century later, the auto industry is starting to look again at how drivers should look back. As federal regulators finalized a long-awaited mandate for rearview cameras last week, Tesla Motors and the Alliance of Automobile Manufacturers, automakers' main Washington lobbying group, filed a petition with the National Highway Traffic Safety Administration seeking permission to replace side mirrors with cameras.
The switch has promise on paper. Cameras are smaller than side mirror assemblies, so they could help aerodynamics and fuel economy. They also can be placed just about anywhere on the vehicle, whereas mirrors have to be installed in the driver's line of sight.
Letting automakers use cameras would help them "innovate and address field of view, fuel economy and aerodynamics challenges for specific segments of vehicles," Tesla and the alliance wrote in their petition.
But just as Harroun had to fight for his mirror, the age of mirrorless cars will not come easy. Despite the appetite for technology, regulators and safety experts worry that replacing mirrors will put people at greater risk.
"With safety as our highest priority, NHTSA will consider the new rulemaking petition and make a decision based on its merits," the agency wrote in an e-mail to Automotive News last week when asked about the petition.
Tesla has been pushing to use cameras in lieu of side mirrors since at least 2012, when the company unveiled a concept version of its Model X crossover that would allow drivers to look at display screens to check their blind spots. (A more production-ready concept shown in 2013 had mirrors.)
Aerodynamics and weight reduction are critical to maximizing the range of Tesla's all-electric cars. And under CEO Elon Musk, the company has prided itself on adopting new technology and never looking back.
But safety experts worry that drivers reliant on cameras and screens won't look back either. Checking mirrors and turning to look at a blind spot have been part of Driving 101 for generations. Those who educate and license drivers recognize that the introduction of backup cameras -- and someday, mirrorless cars -- could lull drivers into complacency, if not done right.
"These technologies are being introduced with the best of intentions," Peter Kissinger, president of the AAA Foundation for Traffic Safety, said in an interview. "But we have to be sure we don't have unintended consequences."
Because automakers put their latest technology into their most expensive cars, it tends to end up in the hands of older buyers. And research suggests that older buyers may be prone to misunderstanding the new technology.
For example, in a 2008 survey by the foundation, about 43 percent of older drivers who owned cars with adaptive cruise control incorrectly thought the technology would bring their car to a halt if it detected a stopped vehicle ahead.
The next generation of drivers, however, will be more comfortable relying on cameras for their bearings. Backup cameras are increasingly common in mainstream vehicles, and the final regulations issued by NHTSA last week will require all new cars to have a backup camera by mid-2018.
The regulations phase in starting in May 2016. Because automakers generally have a product cycle of five to seven years with a freshening halfway through, they should be able to wait for the next scheduled overhaul to add cameras. Mazda, for instance, will add backup cameras to the Mazda2 subcompact and MX-5 Miata convertible when they are redesigned.
"If we have a product that doesn't have a camera, then we're going to do that when we do a midcycle or launch the new model," said Dan Ryan, Mazda's director of government and public affairs. "But a lot of the products have one already."