In answer to McNoodle, originally the m62 was meant to link up with a Liverpool inner motorway such as the one in Leeds. The M62 would have continued along Edge Lane with junctions at Rathbone Road and Durning Road. Junction 1 would have been around Islington. This would have provided a link to the docks and tunnels.
At the time it was built in the early 1970's the country was in a major financial downward spiral and money was tight. To get from Bowring Park Road to the docks would mean a major demolition job of many houses and buildings along the route. The Govt thought that the money could be better used elsewhere and decided to leave the last leg of the motorway until later. Nearly 40 years on and they are just beginning to to the job of improving the Edge Lane route into the city centre (although it won't be as a motorway )