There is a roundabout near me that gets quite low traffic volume. I probably only have to even slow below 20mph about 10% of the time. The bigger risk is that the car in front of me is going to come to a complete stop at the yield sign despite the fact that you can see any potential conflicts at least 100 feet before the roundabout.

American drivers don’t know that a yield doesn’t require a stop and can’t think more than one or two seconds ahead of any possible conflict in traffic.