It runs east to west from junction 4 of the M60 at Gatley, south of Manchester, to Dunkirk, approximately four miles (six kilometres) north of Chester.

With a length of 33.3 miles (53.6 km), it connects North Wales and the Wirral peninsula with much of the rest of North West England, serves business and commuter traffic heading towards Manchester, particularly that from the wider Cheshire area, and provides the main road access to Manchester Airport from the national motorway network.

where it leaves the M60 motorway at its junction 4 (clockwise exit and anticlockwise entry), adjacent to where the slip roads for the A34 to and from Manchester merge and diverge.

Traffic levels on the mainline drop significantly as the motorway begins to assume a more traditional feel (three lanes and a hard shoulder per direction) whilst passing between Broomedge and High Legh.

[2] The concrete multi-span Weaver Viaduct (crossing both the river and its navigation course) immediately follows junction 12 and offers views of the town of Frodsham and its railway viaduct, along with the INEOS chemical plant and Rocksavage Power Station on the opposite side.

Between junctions 12 and 14, it runs parallel to the River Mersey, Manchester Ship Canal, a 400 kV overhead power line and the Chester-Warrington railway.

After meeting the M53 motorway, the road finally returns to two lanes, it proceeds between Chester to the south and Ellesmere Port to its termination at Dunkirk, Cheshire, where it becomes the A494.

[4] The first section, announced in November 1963 by the transport minister Ernest Marples, was a southwards extension of the Princess Parkway from Wythenshawe in Manchester to the A56 and A556 at Bowdon which entered the Trunk Road Programme for 1967/1968.

Work began in 2006 to grade-separate[clarification needed] this junction (and others) to allow free-flowing traffic between the motorway and the A550 at Deeside in North Wales, meaning that the mainline motorway no longer connects to the roundabout (it meets the extended A494 head-on 235 m (771 ft) east),[10] with the former eastbound carriageway retained as an on-slip.

The one-mile section of the two-lane M531 from the A5117 south to the M56 Stoak Interchange, was also opened on 18 March 1981, being built by Leonard Fairclough & Son.

The M531 was originally planned to be extended to cross the Chester bypass, and terminate on the A41 at Upton-by-Chester, west of Hoole.

Where it crosses the floodplain of the River Gowy, the carriageway sits on an embankment made of sandstone from a special-purpose quarry, which was constructed to replace existing peat deposits.

[42] The M53 Mid Wirral Motorway was mostly built in 1971; it was originally planned to terminate on the A41 at Great Sutton, with a continuation of the Chester bypass to cross an east-west trunk dual carriageway, east of the present western terminus of the M56.

[43] A34 – Manchester city centre, Didsbury A5103 – Manchester city centre, Liverpool, Bolton A556 – Northwich, M6 – Birmingham A50 – Warrington, Appleton, Knutsford A559 – Northwich A540 – Chester A5117 – Ellesmere Port Lymm A56 Data from driver location signs is used to provide distance information.

[44] At junction 7 in July 2009, the slip road letting traffic come in southbound along the M56 and turn onto the A556 southbound was closed while the bridge where it crosses the M56 (the Bowdon View Bridge), which for many years had had a weight restriction, was worked on; traffic intending to use it had to carry on to junction 10 and there turn round, or go through the centre of Altrincham; traffic for the nearby Tatton Park Flower Show, and the resulting closure to through traffic of the minor road along the southwest edge of Tatton Park from Ashley, Cheshire to Mere, Cheshire (which would otherwise have acted as a bypass for people living in the area), added to the resulting congestion.

[45][46][47][48] On Saturday 28 February and Sunday 1 March 2015, the new concrete girders of the Thorley Lane bridge a little north of Manchester Airport were put in.

[52][53] "The M56 corridor" is a term used by estate agents and social geographers to describe what is considered to be a relatively affluent area of North West England, within easy reach of the M56.

The area includes the cities of Manchester and Chester, and commuter towns and villages in rural Cheshire.