Dual Carriageway vs Highway

[Vinc]

Since you can do 70 mph on both type of road, what is the difference between the two? Is it a matter of whether it's the state or the borough that pays for maintenance, or is there another more logical difference?

Maybe it's because the speed limit on carriage ways can be reduced and it can not on highways?

Before you say highways can be 3-4-5 lanes; let me remind you that 3 lane carriage ways are not uncommon.

[yorkie_chris]

I presume you mean motorway?

If so there's loads of differences, certain vehicles aren't allowed on the motorway, the speed limit can be reduced on both, the road design tends to be very different in terms of the joining/exit ramp construction, assigned junction numbers etc etc.

[Vinc]

Yes motorway - sry, I get the names wrong all the time. Im not native :)

I think what I don't get is if you can drive equally fast on both, why would the layout not be completely the same, and hence they should be the same thing?

[yorkie_chris]

You can't drive equally fast on both, depending on your vehicle.

For example, look at an A road dual carriageway, there may be T junctions where vehicles can cross the carriageway rather than smooth, safe on/off ramps. Would you want a 7.5 tonner going down there at 70?


Maybe the layout should be the same but if you look at the A1 as an example, there's literally farm entrances onto a dual carriageway. Really not worth making a proper junction for!

[DarrenSV650S]

Motorways don't have junctions. Dual carriageways do

[Messie]

I always understood that the National Spped limit was 70 on motorways, and dual carriageways which have a fixed central reservation.
Therefore on all other roads on which the National Speed limit was 60, even on a dual carriageway if there was no fixed central reservation

[Bibio]

easy way to tell. motorway sings are blue and dual carriageways ones are green.

if your not native to the UK and you plan on staying for a good while then it might be a good idea to read our highway code book.

[Vinc]

Biblo, I appreciate your concern but I was mostly interested in the reason why a dual carriage way can allow the same speeds as a motorway.

I have a full British license which I got here, and a recent copy of the highway code.

Thank you for all your answers

[Spank86]

Yes motorway - sry, I get the names wrong all the time. Im not native :)

I think what I don't get is if you can drive equally fast on both, why would the layout not be completely the same, and hence they should be the same thing?

You can't always drive equally fast on both. Vans and larger vehicles face more restrictions on dual carriage ways due to their inferior construction (mostly entrance and exit roads and occasional u turn spots)


Also 3 lane dual carriageways are pretty uncommon and the motorway speed limit can be, and often is, lowered same as any other road.
.
Therefore on all other roads on which the National Speed limit was 60, even on a dual carriageway if there was no fixed central reservation

How do you get a dual carriageway without a reservation?

[Messie]

A 'fixed' central reservation, ie, when it's NOT a bit of grass or some such.
It was told that a fixed central reservation can be summed up pretty much as crash barriers, although there may be one or two exceptions to this

[Spank86]

I'm pretty sure a pure grass median is still national speed limit unless otherwise signed (not that there are many left these days) as long as the two carriageways are still separated by something.

(When you said fixed I read it as immovable, so not cones)

[Owenski]

How do you get a dual carriageway without a reservation?

I think that's a loose term/misunderstanding, you're right a dc must have a divide otherwise its a single carriageway. What I think Sally means is a solid barrier makes it 70mph limit under nsl which is correct, a soft divide (grass verge for example) restricts the nsl to 60mph.

As for the op a significant difference between motorway and other highway in development and modernisation. Is that the highways agency, own maintain and regulate the motorways nationally where as all other roadways are maintained by the local authority within which they're located.

[Spank86]

Yeah, cheers owenski, I got that now but I still maintain that ANY unsigned dual carriageway is 70 (in a car) regardless of barrier status. As long as its not a single carriageway (no central reservation including grass strip).

[orose]

One of the things that separates the two is the restrictions for vehicles which use them - dual carriageways are general access, except where they prohibit vehicles, while motorways are closed except for the allowed vehicles. One example of this is that the Dartford crossing isn't part of the M25, so that can be used by all sorts of vehicles.

http://pathetic.org.uk/features/special_roads/ is an interesting read, as there are other weird quirks in the special roads (a superset of motorways).

[Fordward]

a soft divide (grass verge for example) restricts the nsl to 60mph

according to a speed awareness course i did last weekend this is incorrect

if there is physical separation of the carriageways ie: more than just paint, then it's a 70 if nsl, ditch grass etc all qualifies as a central reservation

it also doesn't even need to be a two lane carriageway a single lane in both directions on physically separate carriageways is a 70, i never knew that one

[Spank86]

Yup, the dual refers to the carriageways in different directions, not two lanes in one.

I always thought that too when I was a new driver.