The motorway that connects London to its most distant airport is also the main road to East Anglia, rolling across the hills of Essex and Cambridgeshire.
A gallery of images sent in by visitors to the site of original photos of motorways — including some impressive views of the M4 and M11 under construction.
Motorways used to be really simple. Now they have electronic signals, variable speed limits, emergency lay-bys, part-time hard shoulders... Just what is so smart about Smart Motorways?