There was a question on this a couple days ago, but by the time I tried to post on it it was closed, so here goes again.
The question concerned priority to the right in South Africa, even though they drive on the left. I guess the first thing to note, is that for ordinary intersections, it makes little difference where the priority is so long as everyone follows the same rule. But on circles (rotaries, roundabouts, whatever) it makes an enormous difference.
When I lived in a small Swiss city (Fribourg) in 1970-71, there was–and is–a circle adjacent to the Place de la Gare that became chaotic every day around 5. In fact, it turned to total gridlock and one or two traffic cops had to be there every day to let anything move. The reason was obvious. Blind adherence to the priority to the right rule meant that cars coming on to the circle had right of way over cars already there. So in the rare instance that a car did manage to exit from the circle, the result was not that all the other cars could move up one place; instead one more car came onto the circle. The solution was equally obvious, at least to anyone who had ever seen a circle in England. There circles operated as what electronics engineers call an unstable multivibrator. Since circles go clockwise there, while they still give priority to the right, the result is that cars on the circle have right of way over cars that are trying to get on.
Now you might think that once traffic in one direction took over, the perpendicular direction would never get a chance. This would be a bistable multivibrator. Just as leakage of electrongs causes an unstable multivibrator to suddenly reverse directions, so here cars going 3/4 of the way around (so, in England, turning right) cause the circle to suddenly switch. Imagine that two reads meet at right angles, say a NS road and an EW road. And you put in a large circle (you do want a large one for reasons that will become clear). Suppose that all the traffic is now entering from the NS road. If all the cars were going just 180 degrees then that would continue and the EW people would be screwed. But of course, that is not what happens. Some percentage of the cars going north will want to go 3/4 of the way around and exit going E. Any such car will be on thecircle and have the right of way over cars entering going S. This will create an opening that cars going W will exploit to get on the circle. In most instances, most of these will now block the cars heading N from entering the circle and the prevailing direction will suddenly flip and there will be a flow in the EW directions.
Of course, it gets more complicated especially when more than 4 directions come in, but it still works infinitely better than the alternative. The last time I drove in Switzerland, I was warned that their law has changed and that cars on circles nw have priority over those trying to get on. The result is that circles there now operate smoothly. I don’t know if the rest of Europe has also switched, but I assume so. It makes so much sense.
North Americans are basically unaware of any of this since traffic engineers have never relied on priority much (except at 4-way stop signs) and essentially all intersections are controlled by lights or stop signs. I can’t recall the last time I saw a yield sign here, while they are ubiquitous in Europe.
So whatever you think of the logic of priority to the right in South Africa, for heaven’s sake do not try to change it on circles
