Increasingly, concept cars are popping up without mirrors. For example, Kia is expected to roll out a sleek station wagon with no side mirrors. Similarly, Tesla earlier this year provided a glimpse of its Model Y crossover concept, which featured no rear-view mirrors. And BMW unveiled a mirrorless design on an i8 concept car in 2016.

Engineers recently studied automotive mirrors using computational fluid dynamics software and concluded that mirrorless designs would improve the average vehicle’s aerodynamics by about 6%. If spread across all US vehicles, that improvement would save a stunning 145 million gallons of fuel every year.

In 2016 BMW showed off its i8 Mirrorless concept, which uses two small cameras in aerodynamic holders, and a third mounted on the rear windshield. Images from the cameras are projected on a high-res display suspended from the front windshield. In a press release, BMW declared, “Dangerous blindspots have been consigned to the past.”

Still, government approval is needed in order for automakers to take the concepts to production. In 2016, the US National Highway Traffic Safety Administration (NHTSA) approved the Cadillac CT6’s “hybrid” display, which combines a mirror and camera, but it has yet to bless a complete mirrorless design. Some engineers hope the agency will follow the lead of Japan, which last year approved rules to allow automakers to replace vehicle mirrors with cameras. Government approval, however, is just one of the hurdles facing the technology.

One problem with electronic displays is that they present a two-dimensional image. More important, however, is the human eye’s need to readjust to an electronic display. That constant re-focusing becomes a problem for many drivers. Software glitches also present a potential dilemma. If an electronic display fails on a mirrorless car, drivers could potentially be left without rearward vision. Moreover, display cost is an issue, too, especially in entry-level cars.

If replacement happens, many believe the side mirrors will be the first to go. The protuberances are ugly, create aerodynamic drag, and their associated blind spots are the bane of parking-challenged drivers everywhere and for those reasons, mirrors are increasingly being considered for extinction.