A highway configuration featuring two lanes in one direction and a single lane in the other, with the dual-lane side alternating every few miles. This design provides safe passing opportunities on rural routes without the expense of building a full four-lane divided highway. The opposing traffic flows are often separated by a steel cable barrier to prevent head-on collisions.
Heard on the job
We're upgrading the corridor to a 2+1 road to cut down on fatal passing crashes.
Related terms
Climbing lane
An extra lane on an uphill highway grade designated for slow-moving heavy vehicles.
Dualize
To upgrade a single-carriageway road by adding a central reservation and a second roadway.
Head-on collision
A crash in which the front ends of two vehicles traveling in opposite directions strike each other.