Question of the week: Are white matrix speed limits on motorways advisory?
Mon, 27 Jul 2026
Dear Honest John,
"The M4 at Newport is limited to 50mph to reduce pollution. During heavy traffic, the overhead white matrix signs might indicate other, lower speeds, but they are not circled in red.
Are these lower speed limits advisory when the fixed road signs along the same stretch say 50mph within a red circle?"
- RB
Dear RB,
Mandatory speed limits are indicated by a figure surrounded by a red circle, which applies to both matrix signs and permanent physical signs.
The exact wording of the Department for Transport guidance is as follows: "Where variable speed limit signs are mounted over individual lanes or at the side of the motorway and the speed limit is shown in a red circle, the limit is mandatory. Speed limits that are not shown in a red circle are the maximum speeds advised for the prevailing conditions."
You can read more about this in detail on the government website.
Even if a speed limit is advisory, excessive speed beyond this limit that is deemed inappropriate for the conditions could still result in a charge of driving without due care and attention or dangerous driving if witnessed by the police.
