Speed limits and maths

[Dryce]

that's a very good answer, but the road I referred to above is the A74(M), which occupies that murky place between motorways and A roads, but afaik, the M suffix grants it full motorway regulations, hence that road is a motorway. Thus I still don't see why it would be a 70 sign, instead of an NSL sign.

I don't think the suffix/prefix grants it anything. That's just a label for the road to call it something

The important bit is that it is designated a motorway, and that it has signage to tell you that it's a motorway.

There are other AXX(M) motorways. The history of motorway naming is a little bit convoluted as it appears that they didn't sort out the names until well after they started building - there were at least two different numbering schemes that were proposed. The (M) suffix was intended for small sections of motorway that connected routes or bypassed towns. There are other peculiar inconsistencies such as M90 which branches. Both branches are designated M90.

There is no M7 and there have been suggestions to name the M74 / A74(M) as M7.

 

[st4]

. There are other peculiar inconsistencies such as M90 which branches. Both branches are designated M90.

.

Does that happen @ perth by any chance.

The m9 does the same, m9 from dunblane to edinburgh easy enough, but there is an m9 from forth bridge that takes you to near edin airport. Dancy bybass's etc

 

[Dryce]

Does that happen @ perth by any chance.

The m9 does the same, m9 from dunblane to edinburgh easy enough, but there is an m9 from forth bridge that takes you to near edin airport. Dancy bybass's etc

The M90 forks up near Perth with the east branch connecting (well becoming) the A90 to Dundee and the west branch going round the south of Perth to the Broxden roundabout to connect with the A9.

One of those spurs should be called something other than M90.

The M9 doesn't go to the Forth Bridge. It connects with the M8 at Newbridge. It used to be both motorways connected to the roundabout there but then they connected them via the underpass.

The spur to the Forth Bridge is the A8000 and it's a dual carriageway connecting the M9 to the bridge.

 

[Dryce]

The M9 doesn't go to the Forth Bridge. It connects with the M8 at Newbridge. It used to be both motorways connected to the roundabout there but then they connected them via the underpass.

Brain fade on my part. I forgot. What they did was extend the M8 to the A720 Edinburgh bypass and the old bit of the M8 that connected to the Newbridge roundabout became the M9.

 

[fyonn]

I don't think the suffix/prefix grants it anything. That's just a label for the road to call it something

The important bit is that it is designated a motorway, and that it has signage to tell you that it's a motorway.

There are other AXX(M) motorways. The history of motorway naming is a little bit convoluted as it appears that they didn't sort out the names until well after they started building - there were at least two different numbering schemes that were proposed. The (M) suffix was intended for small sections of motorway that connected routes or bypassed towns. There are other peculiar inconsistencies such as M90 which branches. Both branches are designated M90.

There is no M7 and there have been suggestions to name the M74 / A74(M) as M7.

oh yes, there are lots of AXX(M) roads, there's one barely 200 yards from me as I type (the A57(M)).

my understanding is that all AXX(M) roads are classified as motorways and have motorway regulations, however they often do not have the full specification of a proper MXX road. also they may be roads for which motorway regulations are appropriate, ie an a road that only leads to a motorway and from which you cannot get off without going onto the motorway etc.

the (M) suffix is what indicates to road users who look at it on a map, that it is a motorway.

however, all of that is by the by, the A74(M) is still a motorway, so why does it have 70MPH signs instead of NSL, which would mean the same thing.

dave

 

[Dryce]

my understanding is that all AXX(M) roads are classified as motorways and have motorway regulations, however they often do not have the full specification of a proper MXX road.

AIUI there are various MXX motorways that don't meet specification.

M90 is one.

M6 is another.

however, all of that is by the by, the A74(M) is still a motorway, so why does it have 70MPH signs instead of NSL, which would mean the same thing.

I don't think this has anything specifically to do with the A74(M).

I don't recall seeing a NSL sign on a motorway. I would expect the sign to be a speed limit sign.

I don't think NSL signs are actually required on a motorway. The very fact that it is a motorway means that unless otherwise marked that the NSL applies. (i.e the sign is implicit).

 

[fyonn]

AIUI there are various MXX motorways that don't meet specification.

M90 is one.

M6 is another.

yeah, I think axx(m)'s are worse maybe I'm wrong..

I don't think this has anything specifically to do with the A74(M).

I don't recall seeing a NSL sign on a motorway. I would expect the sign to be a speed limit sign.

I don't think NSL signs are actually required on a motorway. The very fact that it is a motorway means that unless otherwise marked that the NSL applies. (i.e the sign is implicit).

you do see NSL signs on motorways, sometimes after sections of roadworks when they are resetting you back to 70 after a while at 50 or somesuch. you also see them on the matrix speed signs[1] on variable speed motorways such as the M25 or the M42[1].

dave


[1] I mean the mandatory matrix speed signs, with the red circle around them. this is, of cours,e on the few occasions when they are showing NSL, and not 40
[2] is it the M42? or the M40? the bit near birmingham anyways...

 

[Dryce]

you do see NSL signs on motorways, sometimes after sections of roadworks when they are resetting you back to 70 after a while at 50 or somesuch. you also see them on the matrix speed signs[1] on variable speed motorways such as the M25 or the M42[1].

You're right - you do find them after roadworks.

Up this side of Carlisle we don't have variable limits as yet but yes - I remember last time I was on the M25 they had a graphic NSL logo type thing above the carriageways when the limit ended.

But I don't recall seeing permanent NSL signs.

 

[fyonn]

You're right - you do find them after roadworks.

sometimes.. but I've already been through that bugbear...

Up this side of Carlisle we don't have variable limits as yet but yes - I remember last time I was on the M25 they had a graphic NSL logo type thing above the carriageways when the limit ended.

But I don't recall seeing permanent NSL signs.

well, not in general no. as you said, motorways are NSL as standard.

okay then, can we think of any AXX(M) roads where the speed limit is 70 where they either don't show signs, or show NSL?

are they showing a 70 sign because the aXX(M) designation doesn't imply NSL perhaps? the a57(m) near me is 50 for it's length so that doesn't count.

hmm.. is this a discussion for SABRE perhaps...

dave

 

[glojo]

I am not really following this but in a built up area with street lighting the speed limit is deemed to be 30mph unless otherwise stated. On Motorways which have blue signage etc then is it fair to suggest the National Speed Limit applies unless otherwise stated.

John