Light controlled roundabouts...another stupid idea
Discussion
They've been putting lights on the roundabouts on Bristol ring road recently and one has finally gone live. During rush hour it almost makes sense, but off peak I have regularly sat there watching an empty r-b until the lights change and let me go.
On friday night however I realised why they do it. All the lights were green, so I could have straight lined the roundabout without backing off. Had there been anyone trying to cross the pedestrian crossing (against their red man) I'd have hit them at at least twice the speed compared to a light free roundabout
Another victory for the road planners
On friday night however I realised why they do it. All the lights were green, so I could have straight lined the roundabout without backing off. Had there been anyone trying to cross the pedestrian crossing (against their red man) I'd have hit them at at least twice the speed compared to a light free roundabout
Another victory for the road planners
To me, the very concept of traffic lights on roundabouts simply highlights the fact that the roundabout was probably not the appropriate choice of junction at that particular spot. If it needs lights in rush hour but ont off-peak, then presumably a light-controlled crossroads with priority to the main road and sensors on the side roads would have done the job far more efficiently and much more cheaply?
Our council must have bought a job lot the way they are putting them in. 2am and I am sat at a red for a few minutes. Bugger all traffic around.
The other night the Culverhouse roundabout in Cardiff, and the new Tesco's junction lights were out. I sailed through, no hold ups. On me way back they were working again. Stuck in traffic and lights again.
The other night the Culverhouse roundabout in Cardiff, and the new Tesco's junction lights were out. I sailed through, no hold ups. On me way back they were working again. Stuck in traffic and lights again.
jmorgan said:
Our council must have bought a job lot the way they are putting them in. 2am and I am sat at a red for a few minutes. Bugger all traffic around.
The other night the Culverhouse roundabout in Cardiff, and the new Tesco's junction lights were out. I sailed through, no hold ups. On me way back they were working again. Stuck in traffic and lights again.
Exactly. I wonder if I can invoice the council for time wasted (and pollution created) on my way home
jmorgan said:....another step towards congestion charging!
Our council must have bought a job lot the way they are putting them in. 2am and I am sat at a red for a few minutes. Bugger all traffic around.
The other night the Culverhouse roundabout in Cardiff, and the new Tesco's junction lights were out. I sailed through, no hold ups. On me way back they were working again. Stuck in traffic and lights again.
They stuck up some "peak time" traffic lights on the Cathedral roundabout in Guildford several months ago. This is a big roundabout with a few lanes and not a lot of traffic - well, not until the lights were put there. I frequently arrive there outside the "peak time" to find it deserted, save for a red light hindering progress and traffic flow. I guess peak time is now a 24 hour affair.
On a separate note: This morning, as happens about once every fortnight, one of the traffic lights was lying on the road about 30 metres from where it should be. The offending car was nowhere to be seen, but I expect they'll increase or council tax again to erect equally badly positioned replacements.
On a separate note: This morning, as happens about once every fortnight, one of the traffic lights was lying on the road about 30 metres from where it should be. The offending car was nowhere to be seen, but I expect they'll increase or council tax again to erect equally badly positioned replacements.
These are something that, done badly, causes chaos. Done well, they actually seem to work.
There are several roundabouts in Milton Keynes with traffic lights, where the timing is effective and they allow everyone entering the roundabout at busy times to get to their destination.
They seem to cause much smaller delays than would otherwise result where the traffic flows solidly from one or two directions, meaning that cars trying to enter the roundabout from other directions simply cant.
There are several roundabouts in Milton Keynes with traffic lights, where the timing is effective and they allow everyone entering the roundabout at busy times to get to their destination.
They seem to cause much smaller delays than would otherwise result where the traffic flows solidly from one or two directions, meaning that cars trying to enter the roundabout from other directions simply cant.
I agree that lights can be frustrating, but sometimes they are very necessary or traffic from some roads wouldn't get a chance to enter the roundabout.
Of course it helps if people obey the signals during the daytime; Handy Cross roundabout, M40 J4. Yesterday lunchtime, bright, dry, no sunshine in anyone's eyes. Our lights go green and we start forward, girl in saxo next to me in hurry zooms off ... and just misses being taken out by a coach running his red light at least 4 seconds after it turned red. She just got past him and we in the other lanes stopped just in time.
(For the locals we were in lane 3 coming from of the A4010 (cinema) direction and the coach was trying to kill everyone while heading for the Cressex exit on the RB.
I see people running reds on this roundabout just about every time I use it. Bl00dy dangerous.
Of course it helps if people obey the signals during the daytime; Handy Cross roundabout, M40 J4. Yesterday lunchtime, bright, dry, no sunshine in anyone's eyes. Our lights go green and we start forward, girl in saxo next to me in hurry zooms off ... and just misses being taken out by a coach running his red light at least 4 seconds after it turned red. She just got past him and we in the other lanes stopped just in time.
(For the locals we were in lane 3 coming from of the A4010 (cinema) direction and the coach was trying to kill everyone while heading for the Cressex exit on the RB.
I see people running reds on this roundabout just about every time I use it. Bl00dy dangerous.
Targarama said:
I agree that lights can be frustrating, but sometimes they are very necessary or traffic from some roads wouldn't get a chance to enter the roundabout.
That's exactly my point.
If the local traffic conditions are such that minor roads don't get a look-in on a roundabout, then its simply the case that a roundabout wasn't approriate in the first place. May as well have a light-controlled crossroads with priority to the main road, with sensors for the minor roads, i.e. main road stays on green "permanently" until there's a queue on the sideroad.
pdV6 said:
I agree that lights can be frustrating, but sometimes they are very necessary or traffic from some roads wouldn't get a chance to enter the roundabout.
That's exactly my point.
If the local traffic conditions are such that minor roads don't get a look-in on a roundabout, then its simply the case that a roundabout wasn't approriate in the first place. May as well have a light-controlled crossroads with priority to the main road, with sensors for the minor roads, i.e. main road stays on green "permanently" until there's a queue on the sideroad.
Depends how many many roads are joining. The junction I talk about above has the A404 (in/out), M40 (in/out), A4010 in/out and two local roads. Who gets the priority. Without the roundabout this would be even more of a mess. They're planning some sliproads/flyovers soon though.
Targarama said:
Depends how many many roads are joining.
Fair enough - I wasn't really thinking of motorway junctions, though; the original post is the Bristol ring road. IIRC most of the roundabouts on it are 4 exit jobs.
Weirdly enough (being a dual carriageway ring road) there tends to be a very defined "main" road at most of the junctions that any idiot could see would block traffic from the side roads. Would have been better to have flyovers & slips, but I guess that would (shock, horror) cost money! I still think a prioritised cross roads would be the best (i.e. cheap) default solution in this scenario.
Just to clarify - as far as I understand it, roundabouts are designed to cater for junctions without the need for any intervention (i.e. lights) and that would be one of the only valid reasons for using one. Others might include situations where there are 5+ roads being linked together at a single junction (due to lazy road engineering or lack of space) or motorway-style junctions where the main road simply has to keep moving no matter what.
Therefore, they should only be used where there is a fairly equal demand from all 4 roads at the junction so that right of way doesn't get dominated by one or two traffic streams. If this isn't the case, either the junction needs to be redesigned or sensibly timed lights need to be installed ("sensible" meaning that the light phasing should be tweaked to cater for expected/actual traffic flow).
Simply sticking a r/b in and then deciding to add lights in order to stifle the natural priority smells of lazy planning to me.
Therefore, they should only be used where there is a fairly equal demand from all 4 roads at the junction so that right of way doesn't get dominated by one or two traffic streams. If this isn't the case, either the junction needs to be redesigned or sensibly timed lights need to be installed ("sensible" meaning that the light phasing should be tweaked to cater for expected/actual traffic flow).
Simply sticking a r/b in and then deciding to add lights in order to stifle the natural priority smells of lazy planning to me.
would anyone prefer the french system, where priority can depend on the town, so you never know if you have right of way, or should stop?
its not too bad over here in comparison
lights that only come on in busy times are preferable to non. There are many motorway junctions that intersect a primary road, where getting onto the island can cause a stationary cars on the motorway slow lane..
Personally I use common sense at night/quiet times. Treat it like a normal roundabout, if its safe to go, I just go. Comes from riding a bike, where you never presume a green light is safe to go, you look anyway, something the above clio driver might benefit from.
its not too bad over here in comparison
lights that only come on in busy times are preferable to non. There are many motorway junctions that intersect a primary road, where getting onto the island can cause a stationary cars on the motorway slow lane..
Personally I use common sense at night/quiet times. Treat it like a normal roundabout, if its safe to go, I just go. Comes from riding a bike, where you never presume a green light is safe to go, you look anyway, something the above clio driver might benefit from.
I guess that the cost of ripping a roundabout out and replacing it is huge compared to sticking lights on.
I agree many lights should be timed, a bit like in Europe where they flash orange at night. The French all think this means they have right of way ...
They put lights on the M4 J6 Southbound junction with the A355. Didn't need them at all. En-route to LHR for those really early flights so driving along at 4:30AM I used to slow right down and use it as a giveway anyway ... nobody about ... just the guy in the CCTV conrol room noting my registration down.
On another topic, I see they've removed the 20mph speed limits along the A355 Farnham Road Slough now too ... another waste of council money.
I agree many lights should be timed, a bit like in Europe where they flash orange at night. The French all think this means they have right of way ...
They put lights on the M4 J6 Southbound junction with the A355. Didn't need them at all. En-route to LHR for those really early flights so driving along at 4:30AM I used to slow right down and use it as a giveway anyway ... nobody about ... just the guy in the CCTV conrol room noting my registration down.
On another topic, I see they've removed the 20mph speed limits along the A355 Farnham Road Slough now too ... another waste of council money.
As pdV6 says it's a dual carriageway with side roads. It should have had flyovers/slips from the start as there are queues at almost every entrance of every r-b throughout the day. Having commuted from 3 out of 4 exits on this particular r-b I would say that all routes have equal priority as plenty of people are turning right (and hence allowing other cars onto the r-b).
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