"Ernest Christley" wrote

I've seen SUV's with what looks like reverse scoops that could have to catch
the air passing over the top of the vehicle and blow it down the back.
Counterintuitive until you realize that attached flow offers less drag.

That scoop helps drag, but more importantly, it prevents carbon monoxide from
entering in the back window when it is open and driving at highway speeds.

When a chopped off SUV has the window open, that low pressure area in the back
gathers up the exhaust, and the swirling motion of the vortex allows some to
enter in though the open window. Not good. The scoop supplies fresh air
flowing down from the top, and keeps the bad air down lower than the open
window.

They have been doing that since the 60's, on old station wagons, before they
cared about mileage and aerodynamics.
--
Jim in NC