Single carriageway

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.

Two-way undivided roads have a yellow center line (and, if there are baseline shoulder stripes, they are solid white on both sides).

This center line may be solid, broken, or a combination of the two, with the different styles, denoting whether passing (which requires a driver to move into the lane used by oncoming traffic) is permitted at a given location.

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.

Central turn lanes are most frequently built in suburban commercial areas where there are a large number of closely spaced driveways (or minor streets).