A21 road

The A21 is a trunk road in Southern England, one of several which connect London and various commuter towns to the south coast. It provides a link to Hastings, East Sussex and parts of Kent. Half of the distance covered is over gently undulating terrain, with some hills and bends. Often traffic is slow-moving, particularly on weekdays on the short single carriageway stretches; and in summer with holiday traffic.
Because of this, people have described the A21 as "a joke" and businesspeople have been reported to "hate coming down the A21". There have been many proposals to upgrade parts of the A21 in response to this.

Parts of the A21 follow the historic turnpike roads: for example the section from Sevenoaks to Tunbridge Wells, opened in 1710; other sections of the road were similarly dealt with later in the century. It is also the location of the first wildlife overbridge in the United Kingdom, near Lamberhurst.
The road between the M25 and Hastings is designated a trunk road, and is maintained and managed by Highways England .

Wikipedia