It is 12 miles (19.3 km) long and provides a link between the M6 motorway and the Metropolitan Borough of Sefton and hence on, via the A5036, to the Mersey docks in Liverpool and Birkenhead.

It starts at Switch Island in Merseyside and passes directly underneath the Merseyrail Northern Line.

Since 1949 an upgrade of the Wigan to Ormskirk route had been proposed to improve traffic flows, yet with the decision in 1961 to develop Skelmersdale as a new town, the proposals were revised to provide a link to the M6 at one end and Liverpool at the other.

[1] The next stage was to connect this road to the M6 and construction on this part began in 1968 and it was opened to traffic in October 1970 as all purpose dual carriageway.

[3] Construction on Switch Island to junction 4 section began in 1978 with the road opening between April and September 1980.