Firefighters tackling a fire after a tanker carrying propane gas burst into flames, have now got the blaze under control.
But the M56 motorway in Cheshire remains closed in both directions between junctions 12 and 15, Runcorn and Ellesmere Port.
Many of the road closures have now been lifted and the initial 1,600-metre cordon has been reduced.
Cheshire police said it had also helped motorists trapped between the incident and road closures to leave the motorway.
The Manchester to Chester railway line has now re-opened, but the Helsby to Hooton line remains shut. Flights to John Lennon Airport are no longer being diverted.
The incident began just before 3pm on the M56 motorway, westbound, but both sides of the motorway were soon closed.
Cheshire Fire and Rescue Service confirmed there had been a risk of explosion but said motorists were evacuated to safety and a cordon put in place.
The tanker is understood to have pulled over to the hard shoulder as the incident began and there were no reports of anyone being injured.
Previous safety advice issued to residents and motorists has now been lifted.
Stretches of the motorway blocked by the incident became gridlocked, with traffic backing up on the motorway and roads network as far as Liverpool and Chester.
Motorists caught in the tailbacks are being asked to remain patient as it may take some time for the congestion to clear.
At the height of the incident, photos posted on Twitter showed motorists on the M56 leaving their sweltering cars to sunbathe outside their vehicles, including pictures of motorists kicking a ball around on the opposite side of the carriageway empty of traffic.