M55 motorway meet junction 4, where the motorway ends and becomes the A5230. The western part of the M55, and the first few hundred metres of the A5230, occupy the route of the old Blackpool Branch railway line. The first motorway constructed in Great Britain was the M6 Preston Bypass, opened in 1958. This ran from the current M6 junction 29 to the M55 junction 1. It was built as a two-lane route. In 1965 the M6 was extended north from what is the current day junction 32 to meet the Lancaster Bypass, and the M6 junction was rebuilt to its current
M6 motorway (Ireland) and the N6 Concessions Limited will be responsible for collection of tolls for a period of approximately 27 years. This scheme was a matter of some controversy at its planning stage. The environmental agency An Taisce claimed that the National Roads Authority's planned route would be "particularly destructive" in passing the site of the 17th-century Battle of Aughrim The decision to toll the route is also controversial, as the M4 motorway to/from Dublin, which connects with the N6/M6 route, is also tolled. This is effect meant that motorists would have to pay two tolls when driving between Dublin and Galway.