 The National Speed Limit, which is lower for built-up areas, only applies in places where a lower numeric speed limit is not in place.The UK has one major single-carriageway motorway, the A38(M), but a number of link roads at motorway interchanges are single-carriageway.In the U.S. the expression "undivided highway" is likely to mean a multi-lane road with only striping (paint) (but no median) between the two directions of traffic flow.