[KaiserPro]

> My experience is that roundabouts help but don't solve. E.g. if there is a complete traffic jam

Agree, when at or near 100% utilisation, its slower than a normal junction.

> you may actually increase the risk of collision due to negotiations about right of way happening every time a car can move forward.

That shouldn't be the case. Ideally you should always have priority from one direction (like in the UK, germany and the netherlands.) The generally rule is that when you come to the round about, if you see someone on your right(in the UK, left everywhere else I imagine) you stop and wait for them to drive past.

> two or three lane roundabouts with complex exit decisions you need to make on a split second

The driving exam will test you for this in the EU. The lane you chose is directly related to where you need to exit. If you are going straight over, or less, then its the outer most lane. Anything more than 180 degrees you take the inner lane. Exceptions will be clearly marked in both floor markings and signs well before entry.