ADUK Archive

Happy New Year all!

Not particularly a bike or car question so thought I'd post it in the car section for a change.

Am keen for others views on what they think the speed limit would be (for a car or motorcycle) on a roundabout where NSL is the posted limit?

An example close to me can be found HERE. Notwithstanding that it appears to lack NSL repeaters in the presence of a streetlight system (I assume repeaters are still necessary on roundabouts??), my assumption is that a roundabout would be treated as a one-way single carriageway road (albeit a circular one) and therefore the limit would be 60 mph.

Others agree/disagree?

Agree!

Technically correct methinks, but irrespecitive of radius to try and get round even the largest roundabout at the NSL is asking for trouble ...

I would assume that any roundabout, unless specifically signed, would just have a speed limit corresponding to the speed limits of the more major approach roads.

I have seen a few roundabouts on NSL roads, where as you approach them, they have a speed limit of 30, then you exit the roundabout following the road, and the speed limit goes back up to NSL.

I've always assumed that this was done because of safety issues with nutters in the past attempting to get around at NSL and being unsuccessful.

Andy, why single carriageway NSL? Its rare for roundabouts to have just one lane (although there's one half a mile from me now!).

Through nothing more than guessing and assumption I'd say 'as per the limit either side'.

Horse wrote:why single carriageway NSL?

Because it is a single- or multi-lane single carriageway.

Gareth wrote:

Horse wrote:why single carriageway NSL?

Because it is a single- or multi-lane single carriageway.

Is it?

What about a sliproad off a DC or motorway?

Gareth wrote:

Horse wrote:why single carriageway NSL?

Because it is a single- or multi-lane single carriageway.

Sorry, don't understand what you mean. I was responding to this:
Am keen for others views on what they think the speed limit would be (for a car or motorcycle) on a roundabout where NSL is the posted limit?

So given that the NSL onto and exit from the junction could be either single or dual carriageway, then I wondered why Andy had plumped for 'single'?

Of course, to add some complication, a single carriageway way can have more than one lane each way, and a dual might hsve just one lane each way . . .

trashbat wrote:What about a sliproad off a DC or motorway?

A on- or off-slip is not a roundabout, and vice versa. Just because they can be connected doesn't make them one and the same.

Horse wrote:given that the NSL onto and exit from the junction could be either single or dual carriageway, then I wondered why Andy had plumped for 'single'?

A dual-carriageway has traffic traveling in opposing directions. Roundabouts generally don't have an anticlockwise traffic flow ... (although there are exceptions).

Gareth wrote:

Horse wrote:given that the NSL onto and exit from the junction could be either single or dual carriageway, then I wondered why Andy had plumped for 'single'?

A dual-carriageway has traffic traveling in opposing directions. Roundabouts generally don't have an anticlockwise traffic flow ... (although there are exceptions).

Hence why I ask about sliproads - they don't have an opposing flow, and yet we will probably all treat them as a continuation of the road they attach to. Well why not roundabouts?

And presumably a motorway roundabout (yes, they exist) is 70mph regardless.

no idea - other than that speeds above 60 might be fun in places!
roundabouts seem to have no standard in how the speed is signposted - I have driven round some where your speed limit would be different depending which road you used to join...
mind you there was a road in Swindon for a while which was 30 in one direction and 40 in the other!

I did though find this website:
http://www.standardsforhighways.co.uk/h ... /index.htm
with instructions on building roundabouts:
http://www.standardsforhighways.co.uk/d ... td1607.pdf
In the absence of knowing the speed you can now build one to standard - sadly quite interesting reading!

Alasdair

I don't think it's sufficient (or correct) to rely on the speed limits of contributory roads as the roundabout in my example has a mixture of NSL DC and SC roads.

My thinking is that it's quite normal that the physical speed limit will increase or reduce within a NSL area depending on road type (SC or DC) so presume this would also be true when negotiating a roundabout too. I struggled to imagine that you could class a roundabout as a DC, although it might be argued that the other side of a largish/squarish roundabout is an opposing carriageway... This sort of begs the question: when is a DC not a DC???

I agree that a roundabout where Motorway Regulations apply will still be 70 mph (unless marked otherwise).

Not suggesting that anyone would attempt to drive at the speed limit on any roundabout, but figured it's useful to know what the actual limit is.

trashbat - good point about slip roads on /off DCs and MWs! I also questioned whether they do definitively inherit the speed limit of the road they join or leave???

Nice find Alasdair - will have to have a read. Another fully subscribed member of the sad club...

I agree this is deep into annorak territory, but you've got to do something to wile away the long winter months.

I do wonder what the speed limit would be on this particular roundabout, as if you're in a speedy enough car, you can get a decent number on the speedometer!

https://www.google.co.uk/maps/@51.4126209,-0.971048,868m/data=!3m1!1e3

TheInsanity1234 wrote:I do wonder what the speed limit would be on this particular roundabout, as if you're in a speedy enough car, you can get a decent number on the speedometer!

https://www.google.co.uk/maps/@51.4126209,-0.971048,868m/data=!3m1!1e3

40MPH signs when you come off the motorway...

Alasdair

akirk wrote:

TheInsanity1234 wrote:I do wonder what the speed limit would be on this particular roundabout, as if you're in a speedy enough car, you can get a decent number on the speedometer!

https://www.google.co.uk/maps/@51.4126209,-0.971048,868m/data=!3m1!1e3

40MPH signs when you come off the motorway...

Alasdair

Ah...

Never noticed them, but I guess that's because we've always been in the second lane whenever we come off the M4 going east.