I am a mere road user and do not claim any expertise in road planning or traffic flow control, but the thinking behind roundabouts where each entrance/exit is controlled by a separate set of traffic lights does puzzle me. Perhaps someone can enlighten me.
We have an example here in the city of roundabouts (Milton Keynes of course) that has recently been converted to such an arrangement (at some significant expense and disruption). It ?governs? a junction between a number of dual track carriageways. I use this roundabout a lot, but have not noticed any significant improvement in traffic flow at peak times. However, it does now scare the s*** out of me on occasions. This is when traffic is stopped on the roundabout by one set of lights and tails back to partially block the previous exit, causing traffic for this two lane exit to converge into one lane. I don?t know if there have been any serious incidents here, but I have witnessed quite a few near misses. This is perhaps exacerbated by the perceived need for MK citizenry to negotiate all roundabouts at as a high a speed as possible, merging with crossing traffic as if training for a motorcycle display team.
Cheers
Robin
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We have exactly the same problem on the Tollbar island to the SE of Coventry. If you're coming from the airport or business park, nothing short of a Ferrari is required to get out into the traffic. the pause between the different sets of lights is virtually nil and so there is no gap created for the non-light controlled exits. You also end up with impatient drivers simply pulling out in front of you - very dangerous.
I'm convinced most road planners cannot drive and have no clue about how traffic behaves.
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I know the tollbar end roundabout, imo its much improved if your only using the entrances with lights but you've not got a chance to get off the business park at rush hour.
Also trying to stick to a lane when its busy is almost impossible as rather than curving they follow straight lines then suddenly angle to the right, an example is going towards london on you drive straight towards the A46 exit then suddenly turn to get back onto the A45 its okay when its quiet but when its busy...
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Robin,
I think I know the roundabout you are talking about - by the Hockey stadium?
My problem with it is that if you are first in line at the lights on red then the lights that fall naturally into view are the ones on he next exit. A number of times I have found myself staring at the wrong set of lights. As for traffic backing up as you describe, I always use the middle and outside lanes going round the roundabout. I do agree it is a pretty poor design especially the bus lane leading to it.
Chris
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Yeah, that?s the one, Chris.
I agree it all gets very confusing.
An example - If I come from the Hockey stadium direction intending to take second exit, I can either take a line to exit on outside lane and can then find stationary traffic not visible on entry to the roundabout blocking my way, or I can take a line to exit on the inside lane and find traffic diving across in front of me to avoid said stationary traffic. Of course, I am aware of this and anticipate, but I have observed others who don?t?
Robin
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I've had the misfortune to use both the MK roundabout AND the Tollbar one in the last 12 hours! Tollbar pretty deserted at 10 on a saturday night, but the lane markings do seem to defy conventional logic.
The one in MK though, is only the 2nd roundabout I hit after collecting (usually VIP) customers from MK rail station during the morning rush to bring them to Bedford for important meetings. They're not often impressed by the lively avoiding action needed to turn right at said roundabout in one piece at that time of day!
There's another one - A1(M) junction 8, Stevenage North. Traffic light control, spiral lane markings and a motorway running over the top so you can never see more than 1/4 of the way round the roundabout! My brother-in-law wrote his Maestro van off there when a lost lorry driver stayed at the same distance from the kerb whilst the lanes moved outward one notch between sets of lights. And you think you only need a Ferrari in Coventry...
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Us lucky folk in Essex have had these idiotic arrangements for many years now.
It still beats me how anyone can imagine that mixing something designed to facilitate a smoot steady flow with something designed to produce intermittent bursts is in any way desirable or useful.
Only on the odd occasions when the traffic lights fail do these junctions work properly.
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Traffic lights on islands do work sometimes....well situated they stop that irritating practice of clogging the island exits so that traffic wanting to cross your line of travel cannot do so due to standing traffic wanting to go straight on but unable to move off the island (remember the do not enter the hatched area until your exit road is clear campaign)- then it becomes a case of "I can't move mate but hah! I'm blocking your exit"
Lights at least give everyone an equal chance as anyone that travels to the 'spitfire island' will testify (named after the steel sculpture of three spitfires outside what is now Jaguar at Castle Bromwich, Birmingham - but used to be the Supermarine 'shadow' factory).
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There are a couple of instances where traffic light on roundabouts DO help. These are where the roundabout is too small to provide a decent separation between the entrance/exit roads, and where there is a preponderence of traffic on one axis which does not leave enough gaps for the traffic on another axis to enter the roundabout.
The Essex example which I am most familiar with is the Army and Navy at Chelmsford, a small roundabout where traffic on one road joining (Baddow Road, could not do so for lack of gaps in the traffic already on the roundabout.
Traffic lights have been added and exit from Baddow Road is now easier, but the lights are on all five roads joining, whereas a better result could have ben obtained with lights on only the two entrances before Baddow Road, thus avoiding the roundabout clogging at the multiple lights.
The gaps between the lights, due to the small size of the roundabout, are too short to move safely across to the appropriate lane, too!
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