There was a freewheel, engaged or disengaged from the dashboard (you can see the control in one of the pics) which meant that when you lifted your foot, going downhill, say, the revs dropped and the car, quite literally, freewheeled just as though you'd engaged neutral..
If I recollect, it was a centrifugal clutch arrangement, and when you accelerated again it drive was restored.
2-stroke Saabs had freewheels, too.