Traffic lights giving cyclists a head start - Bristol

thirdcrank
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Traffic lights giving cyclists a head start - Bristol

Post by thirdcrank »

Interesting clip here which I don't think has been discussed. Traffic lights in Bristol with an extra phase to give cyclists four seconds start.

https://www.bbc.co.uk/news/uk-england-b ... type=share
prestavalve
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Re: Traffic lights giving cyclists a head start - Bristol

Post by prestavalve »

The only reason there is a perceived need for this is because people aren't taking the lane at junctions.
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mjr
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Re: Traffic lights giving cyclists a head start - Bristol

Post by mjr »

I think that's near Broadmead and, if it's where I think it is, some arms have lanes so wide (due to being on a corner and large rigid lorries using it a lot) that it's very difficult to take the lane. Similarly, one in Cambridge I know is on a wide open crossroads where cyclists can take whatever lane position you like and bad motorists will still pass one side or the other.

It also reduces the risk of trying to reach an advanced stop box, as the green bike gives a few seconds warning that motorists are about to get a green light.
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PT1029
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Re: Traffic lights giving cyclists a head start - Bristol

Post by PT1029 »

We have some in Oxford.
The 1st went in at the High St/Longwall St junction. Often in term time 10 or more bikes in the ASL, and often still sorting (not finished) themselves back ino single file when the road narrows (central traffic island - EDIT no island, but waiting oncoming right turn traffic has the same effect) and cars trying to overtake (and buses need to encroach the cycle lane). When installed, cycles had a 10 sec head start, which enabled every one to get back into single file by the time the motors caught up. A post Covid tweek was to increase the head start to 15secs.
In a way, at these locations, there is no need to take the lane (so is a great benefit to slower and/or less confident cycle users - not every one has the confidence or speed required to take the lane), as you have got away before the car behind starts. The main reason for taking the lane (well, the ASL) is because often the RHS is the only space left clear of bikes.
They are now gradually putting these in at some other locations as junctions get their periodic overhaul.
The newest set at (the infamous) George St/Hythebidge St/Worcester St junction are more clever. The advance cycle green only works if a bike is present (I tested this). If no bike is present, the advance green does not operate. I observed one of these, the bike's front wheel was barely in the ASL, but it was enough to activate the advance green.
The sensors used are quite sophisticated, they detect/report back (for data analysis) the number and junction movement of each mode type, so cycle/car/bus.
Originally they needed DfT special permisison, I don't think that is the case now.
Last edited by PT1029 on 14 Apr 2021, 8:02am, edited 1 time in total.
thirdcrank
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Re: Traffic lights giving cyclists a head start - Bristol

Post by thirdcrank »

... The sensors used are quite sophisticated, ...
What system is used?
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Redvee
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Re: Traffic lights giving cyclists a head start - Bristol

Post by Redvee »

mjr wrote: 13 Apr 2021, 3:47pm I think that's near Broadmead and, if it's where I think it is, some arms have lanes so wide (due to being on a corner and large rigid lorries using it a lot) that it's very difficult to take the lane. Similarly, one in Cambridge I know is on a wide open crossroads where cyclists can take whatever lane position you like and bad motorists will still pass one side or the other.

It also reduces the risk of trying to reach an advanced stop box, as the green bike gives a few seconds warning that motorists are about to get a green light.
On the triangle as you come from Jacobs Wells Road going towards Victoria Rooms.
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mjr
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Re: Traffic lights giving cyclists a head start - Bristol

Post by mjr »

Redvee wrote: 13 Apr 2021, 11:32pm
mjr wrote: 13 Apr 2021, 3:47pm I think that's near Broadmead [...]
On the triangle as you come from Jacobs Wells Road going towards Victoria Rooms.
Completely wrong then! What are the lane widths like up there? Is it possible for a lone rider to take the lane easily? I only pedalled up there if I had to!
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Pete Owens
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Re: Traffic lights giving cyclists a head start - Bristol

Post by Pete Owens »

PT1029 wrote: 13 Apr 2021, 7:59pm We have some in Oxford.
The 1st went in at the High St/Longwall St junction. Often in term time 10 or more bikes in the ASL, and often still sorting (not finished) themselves back ino single file when the road narrows (central traffic island) and cars trying to overtake (and buses need to encroach the cycle lane).
In which case it is advisable to not single out and if you are on your own to keep occupying the lane to deter close passes.
When installed, cycles had a 10 sec head start, which enabled every one to get back into single file by the time the motors caught up. A post Covid tweek was to increase the head start to 15secs.
If it is that long then you start to get unintended and undesirable consequences. If you add 15 seconds to each stage of the sequence than that increases the overall length of the cycle by 30 seconds (more if they increase the length of the stage to compensate for the reduced capacity). This means that any cyclist arriving at the junction during the red phase will be delayed for longer. (note that, unlike motors, for cyclists using an ASL the key feature is how frequently a green light comes round rather than what proportion of time it is green)
In a way, at these locations, there is no need to take the lane (so is a great benefit to slower and/or less confident cycle users - not every one has the confidence or speed required to take the lane),
You don't need speed of confidence to occupy the lane - just a sense of self preservation and valuing your life over the wish of motorist to overtake. Of course if you are brave and consider that people driving cars to be more important than you than by all means ride in Oxford's gutter lanes to enable the motors to squeeze past in places where there isn't room to do so safely.

I can see the merits of an advanced green for cyclists - particularly for turning right at larger junctions - to allow cyclists to clear the junction before oncoming traffic gets started - but allowing time for cyclists to scuttle back into the gutter isn't one of them.
as you have got away before the car behind starts. The main reason for taking the lane (well, the ASL) is because often the RHS is the only space left clear of bikes.
The main reason is that other traffic using that lane may be heading in a different direction to you. If you approach side by side within the lane then you could be on crossing paths when the lights change. This isn't so much of an issue if you are sitting in the advanced box in full view of a driver at the motor stop lane before the lights change. It is a problem if you are still approaching the junction to the left of a left turning vehicle when they get a green light. If you see the cycle light turn green that gives you a bit more advanced warning of the need to merge into the main traffic lane.
They are now gradually putting these in at some other locations as junctions get their periodic overhaul.
The newest set at (the infamous) George St/Hythebidge St/Worcester St junction are more clever. The advance cycle green only works if a bike is present (I tested this). If no bike is present, the advance green does not operate.
Which then means you lose the advantage of the advanced notice of tyhe signnal change.
Originally they needed DfT special permisison, I don't think that is the case now.
I think the main concern of the DfT was the ambiguity of the meaning of the green cycle light. In other cases where there are filter lights a green arrow doesn't just mean you are permitted to go, but also that any conflicting traffic is held at red (relevant for right hand turns). I'm not sure whether the same applies with cycle head-start lights.
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Re: Traffic lights giving cyclists a head start - Bristol

Post by Pete Owens »

thirdcrank wrote: 13 Apr 2021, 11:38am Interesting clip here which I don't think has been discussed. Traffic lights in Bristol with an extra phase to give cyclists four seconds start.

https://www.bbc.co.uk/news/uk-england-b ... type=share
The cyclist at 1:11 demonstrates how not to perform a right turn - approaching from the extreme left and swerving in front of a van driver demonstating how not to stop at a red light.
PT1029
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Re: Traffic lights giving cyclists a head start - Bristol

Post by PT1029 »

"If it is that long then you start to get unintended and undesirable consequences. If you add 15 seconds to each stage of the sequence than that increases the overall length of the cycle by 30 seconds"
Because of the traffic flows, the advanced green is only at 1 stop light at the junction, so it is 15 sec per cycle. Like all traffic lights, it is a balance between how often the green light come around, vs short light cycles which results in more time wasted in between green periods..
"You don't need speed of confidence to occupy the lane "
I see where you are coming from, I am happy to take a lane. Being told you should ride out in the road to keep safe/hold up the traffic (depends on your view) is exactly the reason why people don't cycle - they think the roads are just too dangerous/drivers aggressive to cycle safely on..
Being a confident cyclist is fine, but if you want to increase the number of people cycling, you need to understand the view point of thise who do not cycle and offer a solution.
"I can see the merits of an advanced green for cyclists - particularly for turning right at larger junctions - to allow cyclists to clear the junction before oncoming traffic gets started - but allowing time for cyclists to scuttle back into the gutter isn't one of them"
It is a busy urban street with a marked cycle lane (you can see it on streetview if you want). Skuttling back into the gutter is not the intention, just giving cycle users the time to single out having started as a crowd in an ASL box
A wider road would be useful, trying to get land purchase plus a 200 year old stone wall moved in a historic city isn't going to happen. Like a lot of roads, it was designed to a now historic standard (so it is too narrow). LTN 1-20 is very useful, except for old narrow busy/main roads where there is no magic offering. Well, there is, but that is traffic reduction, which while good in itself is rather more long term and complex, and usually has huge opposition - often as much determined by the politics of the local Highway Authority
"What system is used?"
They are some small white box halfway up a lamp post. They were originally introduced not for traffic lights, but to monitor traffic mode movements at busy junctions in order to provide data for future traffic/junction layout planning. After that their use morfed into traffic light management. I don't have the details of how it works, only that there are no data implications as the system does not record faces (which was one of the concerns).
thirdcrank
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Re: Traffic lights giving cyclists a head start - Bristol

Post by thirdcrank »

"What system is used?"
They are some small white box halfway up a lamp post. They were originally introduced not for traffic lights, but to monitor traffic mode movements at busy junctions in order to provide data for future traffic/junction layout planning. After that their use morfed into traffic light management. I don't have the details of how it works, only that there are no data implications as the system does not record faces (which was one of the concerns).
Thanks for that. I used to be something of a traffic light sensor connoisseur because of the problems they can cause for cyclists and some of the garbage trotted out by highwaymen trying to fob off complaints. Technology continues to advance: the days of jumping on the rubber strips are long-gone.
PT1029
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Re: Traffic lights giving cyclists a head start - Bristol

Post by PT1029 »

I'd say the only down side of these sensors is the positioning is crucial, to prevent cyclists (and pedestrians?) from being obscured (and so not recorded) by high sided vehicles.
Our traffic light man is rather more forth coming. The steel cap in his shoe should trigger the lights (wire in road sensors), so there is no reason for bikes not to be detected (chain/cogs/axles should be enough, so don't worry about carbon fiber/aluminium bikes being undetected). If they don't detect you bike, phone the office and most lights sensors could be adjusted from the office.
We know this because we had the head traffic light man give us a talk. Years later it is still deemed the best and most entertaining speaker we have ever had!
thirdcrank
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Re: Traffic lights giving cyclists a head start - Bristol

Post by thirdcrank »

BITD I had the direct dial in number for the head honcho at the Leeds traffic liights.

Anyway, my instinct is that this head start system will only work as intended with universal compliance which IMO would mean camera enforcement. Otherwise, the red+amber is widely interpreted as the signal to go and I fancy this might be just one more scheme to give cyclists a bit of priority which motor cyclists would latch onto. This is IMO just one more example where the traffic authority should be able to do their own enforcement without reference/ deference to the police.
Bmblbzzz
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Re: Traffic lights giving cyclists a head start - Bristol

Post by Bmblbzzz »

Yep, it seems to be 4s from cycle green to car green, only about 3s from cycle green to car red+amber. On the other side they've got a completely separate set of mini lights so cyclists get their own red+amber as well as their own green.
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Re: Traffic lights giving cyclists a head start - Bristol

Post by Bmblbzzz »

prestavalve wrote: 13 Apr 2021, 12:28pm The only reason there is a perceived need for this is because people aren't taking the lane at junctions.
It's not so much a junction as a small gyratory.
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