Plans for a new motorway by-passing the south and east of Birmingham, reaching Tamworth and connecting the M5 and M6 motorways, were announced in 1972. The first section opened in November 1976 linking Birmingham International Airport with the M6 motorway. The curve around the south-eastern side of Solihull opened in September 1985 followed by the section from the M6 motorway with the A5 at Tamworth in December 1985. The southern section of the motorway to Alvechurch just north of Redditch to form a junction with the A441 and from A5 at Tamworth with the A444 at Measham opened in 1986. In 1987 the section to the A38 at Bromsgrove, some south of Birmingham was completed. and then in December 1989 the motorway was completed with the opening of the link from the M5. A planned section north of the M6 running to the M1 near Nottingham was never constructed as planned being replaced by the A42 link, a trunk road which was completed in August 1989 to link with the M1 motorway near Nottingham.
Operational history
Junction 3a was remodeled to give priority to traffic operating between the now westbound section of the M42 and the extended M40 motorway, which opened in stages between December 1989 and January 1991. The section of M42 between the M40 and the M5 was scheduled to be re-designated as an extension of the M40 at the same time, but this re-designation never took place. The section of the M42 between Junctions 7A and 9 was re-built as part of the M6 Toll works and now forms the link between the M6 and the southern end of the toll road. The M6 Toll opened in 2003. Active Traffic Management with hard shoulder running and variable speed limits were introduced in 2006. Since the 1980s, there have been constant plans to build a new service station on the motorway south of Birmingham Airport and the NEC, but this has yet to be built.
Along with sections of the M5 and M6, the southern sections of the M42 form the Birmingham Outer Ring Road motorway around Birmingham. Much like the M25 around London, and the M60 around Manchester, there are areas where this orbital system does not work well. One such point is junction 3A, the link between the M42 and the M40, where traffic is often heavy in the rush hour. The intersection between the M42 and M6 is often very busy too, especially when travelling along the M6.
was launched as a pilot scheme on the M42 operating between junction 3a and 7 with mandatory variable speed limits, hard shoulder running, better driver information signs and a new incident management system. This system allows operators to open and close any lane to traffic in order to help manage congestion or an incident. Since it started in 2006 journey times have decreased by 26% northbound and 9% southbound and journey time variability has decreased by 27%. Due to the success of the trial this system was later extended northbound to junction 9 of the M42 and southbound along the M40 to Junction 15 as part of the first phase of a nationwide roll out of the rebranded 'Managed motorways; concept.
Data from driver location signs are used to provide distance and carriageway identifier information. If a junction extends over several hundred metres and both start and end points are known, both are shown.
