Do I follow roadworks speed limits or smart motorway speed limits when both appear?

Smart motorways are very ambiguous and I genuinely don't know what speed to drive. I drive regularly on the M3 and between junction 4a and 2 is 'smart'. Currently there are roadworks with 50mph speed limit board between junctions 3 and 2. Obviously, I reduce to below 50mph. Then I see an overhead electronic sign with 40, so I slow to 40mph. Next, I pass another speed limit board saying 50. Can I increase to 50mph if the road is clear? Then the overhead electronic sign says national speed limit applies, so can I increase to 70mph? Hard to follow, right? I could presume the lowest limit applies, but whilst in the roadworks, why have a national speed limit sign on the electronic signs when the 50mph limit still applies? I'd be grateful for clarification (with references to the appropriate statutes). Thank you.

Asked on 29 October 2020 by ds797

Answered by Georgia Petrie
Smart motorways are notoriously confusing and unsafe in places. In fact, a study that came out this week revealed that less than half of the drivers surveyed knew how to use smart motorways:

[On a smart motorway] "a speed limit displayed inside a red circle is legally enforceable. If you go over the speed limit, you’re breaking the law and could receive a fine. We’ll let you know when it no longer applies by setting the national speed limit sign. If no speed limits are displayed then the national speed limit applies. When speed limits are displayed, they remain in place until notified that they have ended, or a different speed limit is displayed." Source:

Here is the legislation for variable speed limits specifically for the M3 Motorway (Junctions 2 to 4a):

It says: "A section of a road is subject to a variable speed limit in relation to a vehicle being driven along it if: the vehicle has not subsequently passed—
(i)another speed limit sign indicating a different speed limit; or
(ii)a traffic sign which indicates that the national speed limit is in force."

It's also worth noting that the speed limit when passing roadworks has increased to 60mph in some areas of England:
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