What does the national speed limit sign mean?
The round white sign with a black diagonal stripe means the national speed limit applies. It has no number on it, so the sign doesn't tell you the speed. You have to know it, and it depends on the type of road you're on and the vehicle you're driving. Everything below is for cars (and car-derived vans) that aren't towing, in Great Britain.
1. It means the national limit for that road
The national speed limit isn't one number. For a car it's 60mph on a single carriageway and 70mph on a dual carriageway or motorway. Lorries, buses, vans and cars towing a caravan or trailer have lower limits.
2. Street lights usually mean 30mph (20mph in Wales)
On a road with street lights, the limit is usually 30mph in England and Scotland unless signs show otherwise. In Wales, the default on these roads is 20mph. If you see street lights and no speed limit signs, don't assume the national limit applies.
3. Single carriageway: 60mph
A single carriageway has no central reservation between the two directions of traffic. For cars, the national speed limit on a single carriageway is 60mph. That's the most you can do, not a target: on narrow, bendy country roads you'll often need to go much slower.
4. Dual carriageway: 70mph
For cars, the national speed limit on a dual carriageway is 70mph. What makes a road a dual carriageway is the central reservation separating the two directions, not the number of lanes. A road with two lanes each way and no central reservation is still a single carriageway, so the limit is 60mph.
5. Motorway: 70mph too
Motorways are 70mph for cars, unless signs show a lower limit, such as variable limits on smart motorways or through roadworks. Learner drivers can have motorway lessons in Great Britain, but only with an approved driving instructor in a car with dual controls.
Is it the same in Northern Ireland?
The limits for cars are the same, but learner drivers in Northern Ireland have their own limit of 45mph, even where the national limit is higher. This guide covers Great Britain.
Does this come up in the theory test?
Speed limits are part of the theory test, and the answers come from the Highway Code. Learn the table for cars first: 30 on street-lit roads (20 in Wales), 60 on a single carriageway, 70 on a dual carriageway and 70 on a motorway. Then remember that signs always win.
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