Single carriageway
A single carriageway (
Countries
![](http://upload.wikimedia.org/wikipedia/commons/e/e1/Uk_carriageway_guide.png)
Ireland
The term single carriageway is used for roads in
United Kingdom
The maximum
United States
No equivalent term exists in American English. A single carriage motorway in the U.S. would be termed an "undivided highway"; this is likely to mean a multi-lane road with only striping (paint) (but no median) between the two directions of traffic flow. A road with two lanes of traffic moving in opposite directions would be called a two-lane road.
In keeping with the
Multilane roads use broken white lines between lanes moving in the same direction; at least one solid yellow line lies to the left of the lane which borders traffic moving in the opposite direction, and the right sideline is solid white. Drivers can always tell the direction of the traffic flow by looking at the striping coloration.
Undivided highways with central turn lanes
Since successful experiments in the late 1960s,[citation needed] some urban undivided highways in the U.S. have had a central left-turn lane used by both directions of flow. Essentially, this configuration puts a turning lane in the position of where a median would be if the road were divided.
These roads almost always have an odd number of lanes overall, usually five (two lanes in each direction with a central turning lane), but three-lane and seven-lane versions are not uncommon. Central turn lanes are most frequently built in suburban commercial areas where there are a large number of closely spaced driveways (or minor streets).