It passes Coventry, Birmingham, Wolverhampton, Stoke-on-Trent, Preston, Lancaster and Carlisle before terminating at Junction 45 near Gretna.

[7] In January 1959 the Preston by-pass was closed because of rapid surface deterioration over a stretch of 100 yards (91 m) "due to water freezing and then thawing".

By 1971 the full route was completed between the junction with the M1 motorway at Rugby and the A38 road several miles north-east of Birmingham city centre,[9] including Bromford Viaduct between Castle Bromwich (J5) and Gravelly Hill (J6), which at 3.5 miles (5.6 km) is the longest viaduct in Great Britain.

The motorway engineers here chose to follow the route of the Lancaster and Carlisle Railway engineered by Joseph Locke (now part of the West Coast Main Line) where the motorway runs in a split-level cutting above the railway in the descent from Shap Fell through the Lune Gorge into southern Cumbria.

[15] The northbound entry slip road at Lancaster (Junction 34) was unusually short, presenting problems for traffic joining the motorway.

The M6 crosses the River Lune at this point and unless the bridge had been made wider, there was no space to build a longer slip road.

Across the Pennines, the old road remains the main local through-route, and long-distance fast traffic between Derby and Manchester must instead take either the A50 and M6, or M1 and M62.

[19][20][21] In July 1972, the Minister for Transport Industries, John Peyton, announced that 86 miles (138 km) of UK motorway particularly prone to fog would benefit from lighting in a project which "should be" completed by 1973.

[22] In March 2006, after 15 years of debate,[23] the government authorised the construction of a 6-mile (9.7 km) extension of the M6 from its then northern terminus near Carlisle to the Anglo-Scottish border at Gretna (the so-called "Cumberland Gap"), where it links into the existing A74(M).

[25] The project, which was a mixture of new road and upgrade of the existing A74, crosses the West Coast Main Line and had an estimated costs of £174 million.

The high toll prices, which were set by the operating company and over which the UK Government has no influence until 2054, were blamed for the low usage.

In October 2007, following a successful trial on the M42 in the West Midlands, the government announced that two stretches of the M6 would be upgraded to allow the hard shoulder to be used as a normal running lane during busy conditions under a scheme called active traffic management.

[32] It was then proposed that the system could be extended onto other stretches of the M6 while the government undertook a feasibility study to determine other likely locations for this technology to be used.

[37][38] In July 2006, the government announced its decision to abandon the Expressway proposal, and favoured widening accompanied by demand-management measures,[30] and launched a study to consider options for providing additional capacity.

[51] Download coordinates as: Data from driver location signs are used to provide distance and carriageway identifier information.

[52][53] Each motorway in England requires that a statutory instrument be published, detailing the route of the road, before it can be built.