Variable speed limits are used to manage traffic flow and improve safety, particularly on busy motorways. The speed limit can be changed according to current conditions, helping to reduce congestion, sudden braking and stop-start traffic. Lower limits may also be displayed when there is an incident, roadworks, congestion or another hazard ahead.
When a variable speed limit is displayed inside a red circle, it is a mandatory speed limit and must not be exceeded. Always watch the overhead gantries and roadside signs because the limit can change as you travel along the motorway.
Speed-Limit Example
You are travelling on a motorway where the normal limit is 70 mph, but an overhead sign displays 50 mph inside a red circle. You must reduce your speed and not exceed 50 mph, even if the road immediately ahead appears clear.
Quick Self-Test
Why might a variable speed limit be reduced on a motorway?
A) To make every journey take longer
B) To manage traffic flow or respond to hazards and changing conditions
C) To allow drivers to use the hard shoulder
D) To increase the national speed limit