The route was originally intended to replace the old A6, which it does along the northern section starting with the Preston Bypass. However, a much closer approximation to the overall actual route of the M6 (heading north from its southern terminus) is provided by following the A45, A34, A50, A49, then the A6. South of Preston, the A6 route is instead supplemented by the M61 as far as Manchester, with the M60 acting as a bypass around the city. South of Manchester, there is no true motorway replacement for the old road. The M1 acts as a bypass for long-distance traffic in the south, from the Kegworth junction near Nottingham, to Luton and St. Albans near London; but, it is not an alternative for local traffic as the routes diverge by more than 15 miles while passing through Northamptonshire. Across the Pennines, the old road remains the main local through-route, and long-distance fast traffic between Derby and Manchester must instead take either the A50 and M6, or M1 and M62.