https://www.gov.uk/using-the-road-159-to-203/roundabouts-184-to-190
Of course this is the Highway code in the UK, but if the game followed a few of those rules then roundabouts would make much more sense. The roundabouts are almost treated like junctions with vehicles stopping to let other vehicles on. This shouldn't happen unless traffic is backed up to the roundabout making it impossible to leave the roundabout.
Vehicles waiting to join Roundabouts in the game should be giving way to those already on the roundabout. This doesn't happen.
Regardless of this I'm having fun though, but a few tweaks to how traffic works and flows would be great. Another example brought up on this page would be allowing Emergency Vehicles to use empty lanes etc, even the opposite side of the road if possible would be great.