In the UK we have sections of road that are 3 lanes with the middle lane shared for overtaking as needed.

Example: http://goo.gl/maps/KI48d

One direction (eastbound in this example) has priority as dictated by road markings, and those traveling westbound can use the lane for passing if and only if it is safe to do so. The onus is on them to ensure a safe maneuver.

With a fairly high standard for the driving test in the UK this is totally normal and as far as I'm aware has a similar low rate of accidents to normal 2 lane traffic.