Variable message sign
A gantry structure spanning the road with electronic signals over each lane and a large MS4 message sign on the left.
A 50mph speed limit is shown over all lanes, except the left lane which has a "move left" arrow. The message "stranded vehicle" is shown.
Not long to go until we reach the end of the line now, and the road is about to get narrower quite dramatically. Our fourth lane will vanish at the next exit, usually with a long queue of traffic thanks to the congested roundabout at the end of the sliproad.