It was envisaged that the construction of the Extension of Eccles By-pass through the City of Salford would be carried out shortly after the By-pass was completed in November 1971. Statutory Orders had been published in 1970 by the City Council, as the local highway authority, but little further progress was made prior to the 1 April 1974 when Local Government Reorganisation took place. The Greater Manchester Metropolitan County Council was then created and became the highway authority.

The decision was taken to proceed with the scheme and the firm of G Maunsell & Partners, Consulting Engineers, was appointed to undertake the design and supervision of construction of the dual two-lane carriageway section of motorway.

Originally, it was intended that the motorway would extend as far as the proposed Manchester and Salford Inner Ring Road. However, when this was deleted from the SELNEC Highway Plan, which had been prepared in 1962, it was decided that the M602 should be terminated at a roundabout at Cross Lane, Salford. Subsequently, Regent Road running eastwards from the roundabout was improved to a dual carriageway standard, thereby providing an improved route through to connect with the Mancunian Way.

The 2¼ mile long route runs for almost its entire length on the north side of the World's first passenger railway line, which was opened for business in 1830 between Manchester and Liverpool. Its westbound carriageway was to utilise land occupied by the former 'slow lines' of the railway. At its western end, the route was separated from the railway by the goods lines leading in-and-out of land owned by the Manchester Docks Company.

The scheme required the construction of four bridges carrying side roads over the motorway and the adjacent railway. It was necessary to demolish a footbridge over the railway, and to replace another with a new bridge spanning both the railway and the motorway.

At the Cross Lane interchange the roundabout was to be built over the railway, requiring two bridges. An existing 150 year old bridge over the railway had to be refurbished to provide, along with four subways, pedestrian routes 'through' the terminal roundabout.

The vertical alignment of the side road crossings was severely restricted by adjacent property and the need to provide the maximum possible clearance over the railway, for possible future electrification. In general, precast prestressed concrete beams were used in the superstructures.

The most significant bridge is Cross Lane West with a length of some 550 feet of which 400 feet is fully enclosed, thereby producing a tunnel effect. Consequently, British Rail insisted on lighting being provided for inspection and maintenance purposes. The lower part of each column was to be surrounded by a large diameter concrete pipe set in mass concrete to provide an impact barrier.

As the motorway was to be approximately at the level of the railway for the greater part of its length, an insitu reinforced concrete retaining wall/sound barrier was to be built along the north side of the motorway. It would be provided with a 6 feet 6 inches high parapet to screen the properties. Over one mile long, the wall was to be sloped back at an angle of 1 in 5 to reduce the reflection of traffic noise to properties on the south side of the railway. Noise 'deadening' was to be achieved by means of a regular pattern of deep vertical grooves in the battered face. In addition, retaining walls were required to support the motorway, as it rose above rail level towards Cross Lane.

It had been stipulated that there should be a minimum clearance of 14 feet between the northernmost rail and the boundary fence of the motorway. No open excavation was to be closer to the railway track than a line drawn from the sleeper ends at 45° to the horizontal. Thus abutments and piers adjacent to the railway were supported on bored piles which also had the advantage of avoiding disturbance by upheaval or vibration.

Although designed for the construction of dual two-lane carriageways initially, provision was made for future widening to provide dual three-lane carriageways.

The motorway drainage was designed on the basis of three outfalls, using existing culverted watercourses. However, considerable difficulties were experienced with several old Victorian brick sewers, due to their positions not being accurately recorded.

Although the Greater Manchester Metropolitan County Council was the client, the project was to be financed by a 100% grant from the Department of Transport as a potential Trunk Road.

Before construction of the Main Works, and in order to minimise traffic disruption on local roads, it was decided to build bridges to carry Stott Lane, Weaste Road, Derby Road and Langworthy Road over the line of the motorway. The existing railway bridges on these roads were reconstructed at the same time. In addition, it was decided to construct a new drainage outfall to the Manchester Ship Canal in order to upgrade the surface water outlet from the western section of the motorway. The design of the Canal outlet had to be such as to limit the velocity of the discharge to a level that would not affect the steerage of passing ships. Designs were prepared by 'Maunsell' and Advance Works Contracts were awarded, on which work began in 1980, the 150^th Anniversary of the opening of the passenger railway line.

Tenders for the Main Contract were invited with alternatives of flexible and rigid carriageway construction. In the event, the accepted tender provided for flexible construction, and work began in January 1981.

Property demolition had already been carried out under separate contracts let by Salford City Council. However, it was found that most properties had cellars in which demolition material, eg brick, timber, and plaster, had been dumped. It was, however, necessary to remove it, as an acceptable standard of compaction could not be achieved.

There was more 'unsuitable' excavation than expected, because of extensive soft areas above and below formation, particularly under the westbound carriageway, which was to be built over the former 'slow lines' of the railway. When in use, the 'slow lines' had been provided with 'railway' drainage, but when British Rail decided to remove the two tracks, maintenance of the drainage ceased. The original site investigation had been undertaken in 1970, not long after British Rail had discontinued use of its 'slow lines', and in the intervening eleven years, the drainage had 'clogged' and the clay strata below the original railway trackbed became saturated. The soft areas above and below formation of the eastbound carriageway probably occurred as a result of earlier property demolition which left the ground exposed for several years, resulting in water table changes.

The Contractor programmed to carry out earthworks to formation level for the western third of the Contract, in the first season. A major delaying factor arose due to difficulties met, at the outset, when attempting to locate the existing main sewers crossing the site, to the east of Gilda Brook. A similar but less delaying problem occurred in the eastern third of the Works where the Pendleton Interceptor sewer had to be relocated before major earthworks could begin in that section.

To the east of Stott Lane, a watercourse had been culverted, both to the north and the south of the line of the motorway. It was necessary to establish its condition downstream, as far as the outfall into the Ship Canal. It was found that at one point a partial roof collapse of the brick culvert had occurred, which restricted flow. Remedial action had to be taken before the culverted sections were required to provide the surface water outlet from the western half of the motorway.

In view of the proximity of the motorway to the railway, and the limited verge width, a continuous tensioned corrugated beam safety barrier was provided, where the distance between the back of the hard shoulder and the nearest rail is less than 30 feet. Should the motorway be widened in order to provide the third lanes to the carriageways it would be replaced by a concrete barrier.

Clearly the use of an existing 'corridor' for the M602, by building alongside the railway, had considerable merit, in eliminating the severance of the community, which would have otherwise occurred. However, it had the effect of creating many difficult engineering problems, in such an intensively developed urban area.

The motorway was completed and opened to traffic in December 1982. From Cross Lane roundabout, Regent Road, A57, was upgraded to a dual carriageway standard to connect with Mancunian Way, and Trafford Road, A5603, was widened through to White City.

The effect was a general renewal and upgrading of this part of Salford with the Council selling most of its blocks of flats to housing developers who refurbished them for private sale. The redevelopment of the former Manchester Docks into Salford Quays, and the success of the Trafford Park Development Corporation in revitalising the Trafford Park Industrial Estate; led to an influx of 'new money', and work opportunities.