The M6 motorway in United Kingdom is the longest motorway in that country. Part of it (from M1 to Manchester) is featured in the original Euro Truck Simulator, while the full length of it is featured in UK Truck Simulator and Euro Truck Simulator 2.
The M6 motorway runs from junction of the M1 near Birmingham then heads north, passing Liverpool, Manchester and terminating at Carlisle. Just short of the Scottish border it becomes the M74 which continues to Glasgow.
While in the game a tunnel exists near Cumbria, in real-life the motorway doesn't feature any tunnel.