This idea is fairly simple, but not one which I've seen on
any car, not even a concept. The doors are split
horizontally, with the top half opening upward and the
bottom half opening either outward, like a standard car
door, or downward, like some types of airplane doors.
If the top and bottom
operate independently, then this
could be thought of as a poor man's convertible car.
If there's a mechanical problem, and one half of the door
becomes inoperable, it might be easier to climb over or
duck under half a door, than a standard full door which is
A spring or pneumatic support for half a door would need
to hold less weight than one for a gull-wing style door.
If the top opens up, and the bottom opens down, they
could be connected via chain, effectively counterbalancing
each other, further reducing the need for a spring or other
Making operable windows might be tricky.