Rotaries work by having traffic enter a circular roadway which has some sort of barrier in the center. The barrier can often be a large landscaped island but can sometimes be as small as a disk in the road. Instead of traffic approaching the rotary needing to rely on its turn to determine how it enters the intersection, all cars enter the rotary the same way. The advantages to this are numerous:
- Cars will only enter the rotary when there is a gap in the traffic.
- Cars will not need to signal, and lack of signaling will not cause accidents.
- Cars will not need to ever anticipate the moves of oncoming traffic to turn left.
- Cars will never pause if unsure.
- Cars will always have to slow down when approaching the rotary.
Similarly, exiting the rotary is benefits in the same way. The safety and timeliness of exiting the rotary is always the same, never relying on running a turning signal or crossing a stream of traffic. Backups which often occur at lights where traffic is blocked by a car waiting to turn left, are avoided and the flow of traffic is continuous as long as exiting roadways are not blocked (and this speaks to good rotary design).