One just angled and in many cases held their breath for cleanliness was limited and odor was not.
BUT when ya gotta go, ya gotta go.
Over the years they were replaced with normal toilets. Along the highways stops were normal toilets housed in little buildings usually surrounded by trees and pretty views.
One doesn't forget how to angle, so angle I did.
I must have taken too long (it had been a long time between stops) and suddenly the floor of the toilet, my feet and the bottom of my slacks received a thorough an automatic washing process. I was grateful that my aim was such that only water touched me.
Vive la France.