The smart motorways, between junctions 23 and 27 in Hertfordshire/Essex and between junctions 5 and 6/7 in Kent/Surrey, mark the first use of the hard shoulder as a permanent traffic lane, enforced by new technology and road layout changes, which has led to concerns from road safety organisations about the effects on drivers breaking down.

As part of the traffic management, signals show a red X when a lane is closed. This means drivers must not proceed any further in the lane indicated. This is also true of other sections of motorway, on the M25 and elsewhere, where although there may be a traditional hard shoulder, red Xs are displayed.

John Martin, Highways Agency senior project manager, said: ‘Safety is our top priority. Although our roads are some of the safest in the world we are not complacent and want to remind drivers it is essential they understand the importance of the red X and comply with it.

‘A red X will be displayed because a lane is closed due to an incident or some other obstruction. Driving in a red X lane is dangerous and could lead to prosecution. Remember to follow the red X code.’

Watch the video here.