Why do they deliberately obscure vision at roundabouts?

[TurboHatchback]

On many roundabouts with dual carriageway approaches there seems to be fences or other visual obstructions put in place for no other purpose I can see but to block peoples view of the traffic until they are right on the roundabout.

Case in point: Google map link

What on earth is the point of these? If one has a good early view of the roundabout it allows one to plan the approach, minimise unnecessary braking or stopping and maximise traffic flow. Obscuring the approach just creates the opposite of the above, it increases unnecessary braking and stopping, reduces traffic flow, wastes fuel etc etc. As far as I can see they are up there with traffic calming measures in the category of truly stupid ideas that somehow seem to have made it to completion.

Does anyone know of any good reason for these features?

[73mark]

To make you slow right down,instead of speeding up to beat the cars coming around the roundabout.

[Tuvra]

I noticed this the other day, stupid and annoying.

[CrutyRammers]

^^^ Yes, it's been confirmed several times on here. It's a deliberate policy to make people slow right down.
Remember kids: Visibility kills.

[Mastodon2]

The most annoying for me is when they build the big banked sides and put bushes and trees on top, so you can't get a view of the road ahead on the other side to help plan ahead. It's probably done to stop people racing over the roundabout and off down the road, but it just causes more problems than it solves.

[DMN]

Is it still only installed on the one entry to the roundabout?

If so, I would guess its there to help break up the flow from that entry a little more, and give drivers waiting at the other entries more of a chance.

[anonymous-user]

Paragraph 8.8

http://www.dft.gov.uk/ha/standards/dmrb/vol6/secti...

"Excessive visibility to the right can result in high entry speeds, potentially leading to accidents. On dual carriageway approaches where the speed limit is greater than 40mph, limiting visibility to the right by screening until the vehicle is within 15 metres of the give way line can be helpful in reducing excessive approach speeds. The screening should be at least 2m high, in order to block the view of all road users. Screening can also be used on flared approaches on high speed single carriageway roads where there is a long splitter island."

[Dr Interceptor]

Same here in Farnborough...

https://www.google.co.uk/maps/@51.289975,-0.753369...

[oyster]

Those are there to stop rear end collisions, which are very common at roundabouts.

[Motorrad]

fk em, the solution to this is just keep up the speed and hope for the best.

Their fault if I can't see until the last minute and T-bone some poor fker in my white diesel van (which is even more overweight than me and with tyres balder than my shiny pate).

[TurboHatchback]

OpulentBob said:

Paragraph 8.8

http://www.dft.gov.uk/ha/standards/dmrb/vol6/secti...

"Excessive visibility to the right can result in high entry speeds, potentially leading to accidents. On dual carriageway approaches where the speed limit is greater than 40mph, limiting visibility to the right by screening until the vehicle is within 15 metres of the give way line can be helpful in reducing excessive approach speeds. The screening should be at least 2m high, in order to block the view of all road users. Screening can also be used on flared approaches on high speed single carriageway roads where there is a long splitter island."

Well that would explain their presence but I'm afraid I retain my opinion that they're a bloody stupid idea. The very concept of "excessive visibility" is an oxymoron with respect to driving, yet more pandering to the lowest common denominator of competence .

Maybe one day someone will be able to foist them with their own petard by explaining that by pointlessly forcing everyone to brake and accelerate constantly they are adding to pollution and CO2 emissions and to save the planet we should remove all 'traffic calming measures', speedbumps and stupid visual obstructions .

[robinessex]

Aw come on guys. Stop complaining. We all know speed kills, so slowing everyone down is obviously going to help.

[anonymous-user]

TurboHatchback said:

...more pandering to the lowest common denominator of competence ....

That's it in a nutshell.

Ever wondered why you're not meant to have "right turn" arrows on roundabout approaches? Because they're worried some fking idiot will turn right on to the roundabout, and go round it anti-clockwise. You have to assume there are some very dumb (or easily confused) drivers out there. More than once I've had to stand in front of an old lady to stop her driving the wrong way down a slip road.

TurboHatchback said:

Maybe one day someone will be able to foist them with their own petard by explaining that by pointlessly forcing everyone to brake and accelerate constantly they are adding to pollution and CO2 emissions and to save the planet we should remove all 'traffic calming measures', speedbumps and stupid visual obstructions .

Oi! I design roads for a living. Trust me, for every person wanting restrictions removed, there are 5 people wanting them installed. We PHers are a minority, just a very vocal one. And once the politicos and elected types get involved, you find your (our) options reduce dramatically. We don't fk up the roads for fun - we get ordered to by democratically elected suits.

[cptsideways]

I'm sure some clever sod can work out how fast one could make the entry into a roundabout based on the 15m of visibility & average speed on a roundabout. So say if its clear at 100mph at 70m go for it etc etc


This is purely a mathematics exercise you understand


Otherwise I think they are a stupid idea, along with the white lines making numpties go round the outside of the lane before they are existing

[kambites]

Whilst it's a bit sad people's driving is poor enough that they're necessary, I can't say I've ever really had a problem with them.

[Hangcheck]

Purity14 said:

If everyone decided not to look to the right until they are the lead car at the entrance to the roundabout, there wouldn't be as many rear end shunts at roundabouts.

And traffic would build up as people would drive up to clear roundabouts and have to stop rather than measuring their speed and gearing to enter without stopping.

[williamp]

Is this the same reason why so many new roundabouts have such silly camber to them, and often involve a shatp tuen just before the roundabout??

[Bennet]

If they are spending money doing it, it will have been shown to work. They don't spend money just because someone once had a hunch that it might help.

Too many people: "This doesn't imediately make sense to me, therefore it's stupid."

[rallycross]

its completely stupid - based on having to dumb everything down to cope with the dumbest people on the road.

[heebeegeetee]

TurboHatchback said:

On many roundabouts with dual carriageway approaches there seems to be fences or other visual obstructions put in place for no other purpose I can see but to block peoples view of the traffic until they are right on the roundabout.

Case in point: Google map link

What on earth is the point of these? If one has a good early view of the roundabout it allows one to plan the approach, minimise unnecessary braking or stopping and maximise traffic flow. Obscuring the approach just creates the opposite of the above, it increases unnecessary braking and stopping, reduces traffic flow, wastes fuel etc etc. As far as I can see they are up there with traffic calming measures in the category of truly stupid ideas that somehow seem to have made it to completion.

Does anyone know of any good reason for these features?

Faster traffic on roundabouts actually impedes traffic flow. By slowing the traffic down gaps are created which allows more traffic onto the roundabout. I guess it's the last resort before putting traffic lights on the roundabout.