My running club used to compete in the famous Manchester to Blackpool relay which has now been cancelled due to the increase in traffic en-route in recent years. It was a fairly quiet route for the most part heading out from Heaton Park, through Salford, Bolton, Chorley (there's an area there now which has grown out of all proportion), Leyland, then onto very quiet roads towards the rural and flat Lancashire coast and finally through Lytham into Blackpool. I'll try and dig up an old copy of the route.