Scottish speed limit puzzle

[mtbc]

Driving in England, I often see national speed limit signs which implicitly specify a speed limit that depends on the road one's on and the vehicle one's driving on it. There are also speed limit signs stating a specific number, often 30 or 40, which I believe limit all vehicles identically, at least the Highway Code doesn't seem to add any obvious caveats suggesting otherwise. These signs seem agreeably easy to interpret: one is ordered to apply either the defaults or the given number.

Driving the moving van, I became more aware of those defaults because the limits for such vans are different. It was but a modestly sized van but still limited to 60mph on dual carriageways. I got to thinking of the larger lorries that even on motorways are limited to 60mph and wondered about signing I had seen on Scottish sections of motorway that bear a 70mph sign instead of a national speed limit sign.

What on Earth do those mean? Are there any 70mph signs in England too? Can a large articulated lorry really travel at 70mph on these roads? If not, where is the section of the Highway Code that tells me that?

Comments

[fred_mouse]

Oh, that's interesting. I don't remember seeing the 'national limit' signs, but friend and I were only driving for little bits in the time we were in the UK.

The Australian equivalent is that the speed limit signs are the car speed limits (and used to be that people with learners or provisional licences had different limits), and the minimum of that and the limit for the vehicle you are driving applies. So, 110 km/h zones are exactly the place one gets stuck behind a large car towing a caravan, because their speed limit is 100 km/h.

[mtbc]

The national limit signs here are a round white sign with a diagonal black stripe across, very intuitive indeed. I think what you describe for Australia is what I encountered in at least some US states though now I forget which. I wonder if what actually applies here is some minimum of national limit and posted limit but, if so, the Highway Code certainly ought to say.

[fred_mouse]

The sign you describe used to be the 'no limits' sign here. Once upon a time that literally meant that the section of road you were on had no required limit; it now means whatever the state maximum limit for your vehicle type. They are pretty rare to find though, because over time they have been replaced with explicit rather than implicit limit signs. I have a vague memory of encountering one somewhere in recent years, but couldn't say where.