Quote Originally Posted by SadieKate View Post
Priority to the right: the "Priorite a droite"
This strange rule only applies when driving in France, so it causes much confusion for forign drivers. This rule basically states that when driving along a road, anyone joining from your right hand side has priority over the main road on which you are driving, regardless of the size of the adjoining road. The joining car does not have to stop - you do! This law is thankfully not widely used any more, but in certain roundabouts (like some main roundabouts in Paris for example) you will still see cars stop as the traffic from the right joins. On the expressways this rule doesn't apply anymore.
http://www.driving-in.com/france/

In Oregon (as I think all of the US) merging traffic must match speed or yield. The vehicle in the roundabout has right of way.

Germany has a similar rule... The driver farthest to the right has the right-of-way unless there is a traffic sign to the contrary. Here we have a "first-come, first-served" rule, and the on-the-right rule typically applies only when two drivers arrive at an uncontrolled intersection at the same time.

"First-come, first-served" also means that a driver already in a lane has the right-of-way in that lane over somebody who wants to merge into it. That's why you need to check behind you for overtaking traffic and yield to that traffic before shifting lanes or moving laterally on the roadway. In most places in Europe, if you get rear-ended in such a situation, you get ticketed for "failure to clear to the rear" under this same rule.