The motorway starts at junction 3 of the M20 and heads west, encountering almost immediately the single junction along its length where it has an interchange with the A20. This junction is numbered 2a to reflect its proximity to the M20's nearby junction 2 a short distance to the north-west. to the west the M26 merges with the M25 at junction 5. There is no exit from the M26 at junction 5 and all traffic must join the clockwise M25. The next M25 junction, number 6, is west at Godstone so traffic joining the M26 at Junction 2a cannot leave the motorway for, the longest distance between motorway exits in the UK. Anti-clockwise direction from the M25, the main carriageway continues directly on to the M26 at junction 5. To remain on the M25, traffic must turn on to the slip road which connects to the M25 spur coming north from Sevenoaks, which is multiplexed with the A21. The awkwardness of junction 5 is a result of the history of the two motorways' planning and construction.
History
Construction of the M26 began in 1977, although a route on a similar alignment was originally proposed in the Greater London Plan in 1944 as part of proposed post war improvements to London areatransport network. Those proposals were developed further in the 1960s as part of the London Ringways plan and the route of the M26 at that time formed part of Ringway 4 and would have been designated as part of the M25. Construction of the first part of the M25 began in 1972 but before it opened, plans for the London Orbital motorway were modified to combine the southern and western part of Ringway 4 with the northern and eastern part of Ringway 3. To connect the two separate routes, which together were numbered as the M25, an additional section of road needed to be planned and the M25 route was diverted northwards from junction 5 to meet Ringway 3 at Swanley. The remaining section of Ringway 4 became the M26. Until February 1986, the anticlockwise M25 simply became the M26 at Junction 5, as the M25 between Junction 5 and Junction 3 was not opened until then.
Proposed developments
New junction
has been in talks with the Highways Agency over a possible new junction with the A225, allowing direct access to Sevenoaks – or access to the A21 at the M25 junction.
