CD Lanes

CD stands for Collector/Distributor Lane, which despite the name, is a separate carriageway alongside the main route intended to separate traffic wishing to continue along a route from traffic wishing to enter or exit, preventing a phenomenon known as weaving. Typically these are used on congested lengths of road with multiple interchanges in quick succession.

Where an additional lane is used as part of the main carriageway between two junctions, this is known as an auxiliary lane. These are typically divided from the through lanes by different road markings, for instance on the M4 between Junctions 42 and 43.

The first example in the UK was at Almondsbury Interchange on the M5. Later, and larger, configurations were built on the M1, M20, and M60 as part of their respective widening schemes.