Video images from three cameras are stitched together for display in the rearview mirror. The composite image eliminates blind spots caused by the C-pillars. And the side mirrors are half the size of conventional mirrors -- thus lighter and more aerodynamic than full-size mirrors.
It's unclear whether automakers will opt for a hybrid side mirror. The Cadillac CT6 and XT5 and Chevrolet Bolt feature Gentex rearview mirrors. Motorists can use them in conventional fashion, or they can see a video feed from a single rear-mounted camera.
But those models sport conventional side mirrors. Getting rid of side mirrors would significantly reduce weight, drag and cost.
In 2014, the Alliance of Automobile Manufacturers and Tesla petitioned the National Highway Traffic Safety Administration to allow the substitution of cameras for side mirrors.
The agency hasn't ruled yet, so automakers have been tinkering with hybrid mirrors.
Honda Motor Co. introduced a hybrid mirror dubbed LaneWatch in its 2013 Accord. When the motorist signals a right turn, a camera mounted on the right side mirror feeds a video image to the console screen.
But some motorists apparently found it distracting, and Honda has introduced a conventional blind-spot detection system on some models.
Downing argues that motorists find it intuitive to see a video display in the rearview mirror, Cadillac-style. But suppliers are trying other approaches.
Continental AG, for example, has developed side cameras that feed video images to display screens mounted just inside the A-pillar. In theory, that would allow automakers to eliminate the mirrors without jarring motorists.
Gentex has no production contracts for its hybrid side mirror, but Downing believes the product will cater to car buyers' innate conservatism.
Said Downing: "Consumers appreciate evolution rather than revolution."