The construction of the 11½ mile Lancaster By-pass section of the M6, the County Council's second priority, had followed a year after the work on Preston By-pass had started. In many respects, it was similar, for example, it would also have dual two-lane carriageways with a wide central reservation for the future addition of third lanes.
Following extensive public consultation the statutory procedures had been completed without difficulty. It had been considered to be necessary, however, to move a section of the line at the southern end from that originally proposed in order to avoid a major objection, as it passed through land designated for the building of the future University of Lancaster. The effect was to take it through a wooded area which, no doubt in later years would have brought vociferous protests from environmentalists.
By-passing the City of Lancaster on its eastern side, with connection to the A6 at each end, it was not the intention to provide an intermediate interchange as part of the project. However, the Road Plan for Lancashire had included a future proposal for a motorway link road to Morecambe and the port of Heysham, to connect with the By-pass by means of a two-level interchange at Halton, on the north side of the River Lune. It was accepted that this was unlikely to be constructed for many years and, therefore, serious concern was expressed at the difficulties likely to be experienced by the emergency services in gaining access to the By-pass.
The only road of any importance crossed by the By-pass is the A683, leading from Lancaster north-east-wards along the south side of the River Lune. The emergency services were based in the City and it was decided that a connection should be provided for their sole use, with the County Council agreeing to pay 25% of the cost. The design standards of this junction were lower than those of a normal interchange, with the carriageways of the slip roads separated only by double white lines. Subsequently, however, local representations were made for the junction to be opened for general use and this was eventually agreed. The result is a unique sub-standard interchange on a British motorway (see later).
A total of 27 bridges was required. The major obstacle along the line of the By-pass was, however, the River Lune. The design chosen for the 400 foot long bridge at Halton incorporated a reinforced concrete open spandrel fixed arch with a clear span of 230 feet and a rise of 44 feet. Because of their width, bridges carrying motorways are normally designed as two structures separated by a narrow gap. In casting such a large arch, massive support is necessary and the Contractor built a temporary timber gantry across the river to carry the scaffold and shuttering for the first half. On completion, this was lowered slightly, winched sideways as a complete unit on to a second gantry, raised to the correct level and used to form the second arch. Users of the motorway are, unfortunately, unaware of this impressive bridge in such an attractive setting.
Work on the construction of the By-pass was well advanced before the problems experienced on Preston By-pass became apparent. In view of the close proximity of major limestone quarries in the Carnforth area at the northern end of the By-pass a sub-base of this material had already been specified, but it was only possible, at that late stage, to introduce a few of the other desirable design changes.
A 'positive' drainage system was installed and the carriageway construction included the laying of a 4½ inch thickness of hot rolled asphalt, as the permanent surface. Hard shoulders were provided shortly after the by-pass had opened, even though they were not continuous at bridges. In about 1968, a third lane was constructed in each direction taking advantage of the extra width provided in the central reserve.
With difficult ground conditions similar to those experienced at Preston, and the bad weather during the same period, delays and disruption were inevitable, but the By-pass was opened to traffic in April 1960. The extension to Carnforth was not opened until 1961/1962 and traffic left the Lancaster by-pass on substandard link roads onto the A683 until the extension was opened.
At the northern end of the By-pass, at Carnforth, a one mile long link road provided the connection to the A6, and was subject to the motorway traffic regulations.
In due course, when the M6 was extended northwards a grade-separated roundabout interchange was constructed but the link road was not designated as A601(M) until the Quarry Link Road (described below) was opened.
On the east side of the M6, large quarries had been worked for many years. The main access was via the B6254 which ran from the centre of Carnforth and crossed the M6 immediately south of the interchange. In the mid 1980's, a short single carriageway link road was built to connect the B6254 to the interchange roundabout, and this was (quite illogically) designated A601(M). Quarry traffic was, therefore, provided with direct access to the M6, thus giving considerable relief to the town.
Pressure for a full "proper" interchange, and the link road to Morecambe grew from both the Highways Agency and the County Council and the Statutory processes for a scheme that met both of these requirements were commenced. The final objection was overturned in 2013 and work on the £124.5m scheme commenced in December of that year.