[1] It is also part of two other roads: the A57 to the west, which runs east–west through Greater Manchester linking the M602 and M67 motorways, and a short section of non-motorway A635 to the east.

It then runs for around 3⁄4 mile (1.2 km) before reaching its junction with the A6 which it crosses on a bridge before dropping down to ground level.

It would be the first elevated main road to be built outside London, and the UK's second aerial motorway after the Hammersmith flyover.

The spans are made out of precast concrete, with hollow box-units post-tensioned to form a spine beam.

Testing of the design was carried on a 1/12th model at the Research Station of the Cement and Concrete Association at Wexham Springs in South Bucks.

The second stage was the construction, from December 1964, of a 0.6 mi (0.97 km) long elevated highway of a motorway standard which ran between the A6 and A56 roads.

The previous day it was opened to pedestrians, who were allowed to walk the whole of the high-level route as a sight-seeing publicity exercise.

Leonard Fairclough & Son were the contractors, and the prestressed concrete sections were made at its operations in Adlington, Lancashire.

The piling was completed by Pigott Foundations of Ormskirk with auger (screw) boring with reinforcement cages.

In 1992, the westbound junction was rebuilt to replace a temporary flyover, whereby the A56 passed over a roundabout where the A57(M) originally ended.