Choosing what type of doors you want on your new model - regular-opening or sliding - could be part of the car-buying experience within three years.
Engineers in the US have unveiled a system on a Smart ForFour that gets rid of the rail on the side of a vehicle, as seen on the Peugeot 1007 and Citroen C8. The track is hidden inside the cabin, so door type has no impact on exterior design.
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