>>4474 Potentially a good idea if drivers understand it.
The biggest worry I have is that people in cars will assume they have the right of way exiting a roundabout, where cyclists will be going straight around without stopping. There's going to be at least a fair amount of near misses where cars slam their brakes on right before the crossing.
The other problem would be cars waiting to enter the roundabout blocking the cycle lanes, especially lorries.