Bus controlled traffic lights

brynpoeth
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Re: Bus controlled traffic lights

Postby brynpoeth » 17 Mar 2019, 8:23am

Many French towns have built new tram systems in recent years, even Paris
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wjhall
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Re: Bus controlled traffic lights

Postby wjhall » 18 Mar 2019, 11:14am

'We' are not letting go of bus lanes, but taking them over, remember, this is a cycling group, I think.

The point is that the signals would be optimised to blow the whole half mile congestion plug through with the bus. On a 20 mph road this would take 90 s after which some other optimisation would resume, probably weighted for a while against the bus route, until the next bus bearing plug appeared. Eventually, with frequent enough buses, this would completely close side roads, but since in many places we are talking about 5 minute intervals as suitable for trams, this will be some way in the future.

Closing side roads seems to be the basis of the current Bristol proposals for the A4018, but by repainting road markings rather than traffic light sequencing. Being well beyond what would be needed for any plausible bus frequency suggests that the real purpose is to accommodate a much increased flow of general traffic from new developments to the north of the city, bus lanes being used as a cover for this.

Bus lanes have the effect of speeding buses from one congestion point to another, after which, without bus control, they could get stuck for up to a light cycle.


The railway analogy is useful. Consider the way in which regulation and control are used to allocate priorities and trains between loops, fast/main and slow/relief lines.

The situation described in Leeds seems to be a good example of creating something that is apparently designed to favour buses and cyclists, but not sufficiently actually to have much effect.

I am currently reading a paper about systems in Melbourne (3) drawn to my attention on another forum. Interestingly it is dated 2018, suggesting that these systems are fairly novel, despite the technology being well established. I had expected to be deluged with comments on the lines of 'surely you know this has been done everywhere for ages'.

(3) Bus & tram priority in Melbourne – conference paper
http://www.jctconsultancy.co.uk/Symposi ... tralia.pdf

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Re: Bus controlled traffic lights

Postby Bmblbzzz » 18 Mar 2019, 12:23pm

wjhall wrote:'The point is that the signals would be optimised to blow the whole half mile congestion plug through with the bus.

That would require half a mile (more in fact, if the cars are to be moving) of uncongested road beyond the signals. That's not going to happen with current vehicle usage.

Closing side roads seems to be the basis of the current Bristol proposals for the A4018, but by repainting road markings rather than traffic light sequencing. Being well beyond what would be needed for any plausible bus frequency suggests that the real purpose is to accommodate a much increased flow of general traffic from new developments to the north of the city, bus lanes being used as a cover for this.

Interesting and highly plausible idea.

Bus lanes have the effect of speeding buses from one congestion point to another, after which, without bus control, they could get stuck for up to a light cycle.

Yes. As a start we could at least make bus lanes continuous. Signal optimisation would help too, but without dedicated bus lanes it just means the lights are optimised for one set of congestion over another.

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Re: Bus controlled traffic lights

Postby Pete Owens » 18 Mar 2019, 5:40pm

wjhall wrote:'We' are not letting go of bus lanes, but taking them over, remember, this is a cycling group, I think.


Not only do we already use bus lanes – but these are the ideal cycling environment (even from a segregationist perspective). They present a virtually motor traffic free environment – Not only are buses relatively infrequent, they also make progress at approximately cycling speed; even if you were to ride the entire length of a bus lane on a busy bus route you are unlikely to encounter a single bus.

Unlike a cycle path you will not find your passage obstructed by trees, bollards, fences, bins, or other objects – and if the route is following a bus route then you can guarantee that you will find bus stops en-route. Unlike a cycle path you will not have to give way at every side road or private drive. Unlike a cycle path, a bus lane is guaranteed to be of adequate width. And when you reach a set of traffic lights you will get a stage in the lights that will enable you to clear the whole junction, rather than hop from cattle pen to cattle pen at times to suit the convenience of motorists.

So yes, what you are advocating is giving up the best cycle facility there is and replacing it with something that will almost certainly be vastly inferior. And that is without considering the loss of utility to bus passengers. People have very little incentive as it is to take the bus. If you cause them delays then some will switch to cars.

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mjr
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Re: Bus controlled traffic lights

Postby mjr » 18 Mar 2019, 6:23pm

Not only do we already use bus lanes – but these are the ideal cycling environment (even from a segregationist perspective). They present a virtually motor traffic free environment – Not only are buses relatively infrequent, they also make progress at approximately cycling speed; even if you were to ride the entire length of a bus lane on a busy bus route you are unlikely to encounter a single bus.

Anybody tempted to believe that should go ride Euston Road or the bits of CS7 that are still only bus lanes. Then compare with the bits of CS6 or CS3 which are built to recent standards (so no obstructions by trees and so on, priority over side roads and adequate width).

There's simply no comparison between enjoying a proper cycleway and riding along trying to sprint to keep ahead of the following bus, wondering whether the next motorist to put your life in danger will be a bus, a black cab, a chancing-it minicab or simply a regular motorist not looking before pulling into the bus lane.

And when you reach a set of traffic lights you will get a stage in the lights that will enable you to clear the whole junction, rather than hop from cattle pen to cattle pen at times to suit the convenience of motorists.

Aren't bus advance start phases still really really rare? Most of Norfolk's bus lanes evaporate before the lights, dumping you in amongst a load of turning motorists with at best and Advanced Stop Line if you're lucky to get a half-second start on the motorists behind. The one I can think of which goes all the way up to the lights, outside King's Lynn Rail Station, is not available for cycling (and it's not particularly needed, with a 3.5m cycleway next to it).

So yes, what you are advocating is giving up the best cycle facility there is and replacing it with something that will almost certainly be vastly inferior. And that is without considering the loss of utility to bus passengers. People have very little incentive as it is to take the bus. If you cause them delays then some will switch to cars.

I think there should be bus lanes - but they're very poor cycle lanes and should be as well as, not instead of. They might be OK on low-priority routes, which seems to be how most of central London is going, with the cycle route network slowly developing to avoid bus lanes on bus roads. They're available if you like the extreme sport and big roads, but you're not often directed to use them any more.
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Bmblbzzz
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Re: Bus controlled traffic lights

Postby Bmblbzzz » 18 Mar 2019, 7:11pm

mjr wrote:
And when you reach a set of traffic lights you will get a stage in the lights that will enable you to clear the whole junction, rather than hop from cattle pen to cattle pen at times to suit the convenience of motorists.

Aren't bus advance start phases still really really rare? Most of Norfolk's bus lanes evaporate before the lights, dumping you in amongst a load of turning motorists with at best and Advanced Stop Line if you're lucky to get a half-second start on the motorists behind. The one I can think of which goes all the way up to the lights, outside King's Lynn Rail Station, is not available for cycling (and it's not particularly needed, with a 3.5m cycleway next to it).

Pete Owens will be along sooner or later to explain, but where do you get this idea of bus advance start phases from? They are, as you say, really rare and he certainly didn't mention them. I presume he was just referring to the normal traffic light phase, which gives enough time to clear the whole junction. I'd note that, at least outside London, cycle advance start phases are also really rare, as are cycleways which maintain priority over side roads -- hence being forced to jump from pen to pen.

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Re: Bus controlled traffic lights

Postby Bmblbzzz » 18 Mar 2019, 7:18pm

Pete Owens wrote:
wjhall wrote:'We' are not letting go of bus lanes, but taking them over, remember, this is a cycling group, I think.


Not only do we already use bus lanes – but these are the ideal cycling environment (even from a segregationist perspective). They present a virtually motor traffic free environment – Not only are buses relatively infrequent, they also make progress at approximately cycling speed; even if you were to ride the entire length of a bus lane on a busy bus route you are unlikely to encounter a single bus.

It's a car type of cycling speed though. The average speed from origin to destination may be similar but the peaks are significantly higher and there's far more standing time. Cycling in a bus lane means being continually overtaken by one or two buses and passing them when they're at stops; probably preferable to the same with a multitude of cars though.

Unlike a cycle path you will not find your passage obstructed by trees, bollards, fences, bins, or other objects – and if the route is following a bus route then you can guarantee that you will find bus stops en-route. Unlike a cycle path you will not have to give way at every side road or private drive. Unlike a cycle path, a bus lane is guaranteed to be of adequate width. And when you reach a set of traffic lights you will get a stage in the lights that will enable you to clear the whole junction, rather than hop from cattle pen to cattle pen at times to suit the convenience of motorists.

All true, sadly.

So yes, what you are advocating is giving up the best cycle facility there is and replacing it with something that will almost certainly be vastly inferior. And that is without considering the loss of utility to bus passengers. People have very little incentive as it is to take the bus. If you cause them delays then some will switch to cars.

Yep, bus lanes are for buses and their passengers (and indirectly therefore beneficial to everyone who eg breathes).

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Re: Bus controlled traffic lights

Postby mjr » 18 Mar 2019, 7:25pm

Bmblbzzz wrote:
mjr wrote:
And when you reach a set of traffic lights you will get a stage in the lights that will enable you to clear the whole junction, rather than hop from cattle pen to cattle pen at times to suit the convenience of motorists.

Aren't bus advance start phases still really really rare? Most of Norfolk's bus lanes evaporate before the lights, dumping you in amongst a load of turning motorists with at best and Advanced Stop Line if you're lucky to get a half-second start on the motorists behind. The one I can think of which goes all the way up to the lights, outside King's Lynn Rail Station, is not available for cycling (and it's not particularly needed, with a 3.5m cycleway next to it).

Pete Owens will be along sooner or later to explain, but where do you get this idea of bus advance start phases from? They are, as you say, really rare and he certainly didn't mention them. I presume he was just referring to the normal traffic light phase, which gives enough time to clear the whole junction.

"you will get a stage in the lights that will enable you to clear the whole junction" - if it's just the normal stage (phase means something different in traffic light jargon) then you're getting no time to clear the junction before conflicting turning vehicles are present, plus they are currently timed for motorists and often don't give sufficient time for cycling across a large junction from a stop, so cyclists can easily be caught out mid-junction when cross-traffic is released.

If that's what was meant, it's another disconnection of the bus lane fantasists from the reality on our roads.
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Re: Bus controlled traffic lights

Postby Bmblbzzz » 18 Mar 2019, 8:15pm

So what's the difference between stage and phase in this context?

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Re: Bus controlled traffic lights

Postby mjr » 18 Mar 2019, 10:05pm

Bmblbzzz wrote:So what's the difference between stage and phase in this context?

If I remember correctly, a phase is a movement controlled by a signal IIRC so if there are independent left turn, right turn and straight ahead arrows from a direction, for example, that's three phases, but they might all be lit green together and that's a stage. A different combination of greens would be another stage. And so on.

There are better explanations online, even in the traffic signal manuals, but they're longer as well as more precise.
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Pete Owens
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Re: Bus controlled traffic lights

Postby Pete Owens » 19 Mar 2019, 12:06pm

Bmblbzzz wrote:
Pete Owens wrote:
wjhall wrote:'We' are not letting go of bus lanes, but taking them over, remember, this is a cycling group, I think.


Not only do we already use bus lanes – but these are the ideal cycling environment (even from a segregationist perspective). They present a virtually motor traffic free environment – Not only are buses relatively infrequent, they also make progress at approximately cycling speed; even if you were to ride the entire length of a bus lane on a busy bus route you are unlikely to encounter a single bus.

It's a car type of cycling speed though. The average speed from origin to destination may be similar but the peaks are significantly higher and there's far more standing time. Cycling in a bus lane means being continually overtaken by one or two buses and passing them when they're at stops; probably preferable to the same with a multitude of cars though.

No it doesn't because buses are a couple of orders of magnitude less frequent than cars and bus stops are regular - every few hundred metres.
If you set off along a bus lane you will only be overtaken by a bus if it is so close behind you that it catches you up before you reach the first bus stop (ie within a few hundred metres). If you pass the bus stop first then you will stay ahead of the bus for the entire route. The bus may be progressing in bursts of speed interspaced by stationary periods, but it is not going to catch you unless it is travelling at a higher average speed than you are.

Similarly, if the bus arrives at the first stop before you then it will stay ahead. The only way that you will repeatedly interact with it is if you choose to overtake a bus while it is at a stop. Now if you are a faster cyclist and can make faster average progress than the bus then this would be worth your while, but if you are slower or dislike being overtaken then simply wait behind it - and let it disappear up the road. By the time the next bus arrives on the scene you will be a mile away.

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Re: Bus controlled traffic lights

Postby Pete Owens » 19 Mar 2019, 2:54pm

Bmblbzzz wrote:So what's the difference between stage and phase in this context?


In normal everyday language they mean the same thing.

Traffic engineers refer to a stage to mean a particular combination of signals which allow particular user movements through the junction. They will draw a diagram to show the movements that are permitted during each stage - and which stages are permitted to follow it in the sequence. So in a simple cross roads you will get a stage for E-W traffic followed by a stage for N-S traffic followed (if you are lucky) by a stage for pedestrian traffic.
As junctions become bigger more stages may be added for particular turning movements and islands put in to break up pedestrian movements (the shorter each pedestrian crossing is the less time is allocated for the crossing thus maximising the time allocated to vehicles - indeed also most pedestrian crossing can be slotted into stages where the motor traffic is held on red in-any case. While this optimises junction performance for vehicles, it is a pain in the neck for pedestrians who have to wait for a complete cycle of the lights to make each short hop from one cattle-pen to the next.

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Re: Bus controlled traffic lights

Postby Bmblbzzz » 19 Mar 2019, 3:27pm

Pete Owens wrote:
Bmblbzzz wrote:So what's the difference between stage and phase in this context?


In normal everyday language they mean the same thing.

Traffic engineers refer to a stage to mean a particular combination of signals which allow particular user movements through the junction. They will draw a diagram to show the movements that are permitted during each stage - and which stages are permitted to follow it in the sequence. So in a simple cross roads you will get a stage for E-W traffic followed by a stage for N-S traffic followed (if you are lucky) by a stage for pedestrian traffic.
As junctions become bigger more stages may be added for particular turning movements and islands put in to break up pedestrian movements (the shorter each pedestrian crossing is the less time is allocated for the crossing thus maximising the time allocated to vehicles - indeed also most pedestrian crossing can be slotted into stages where the motor traffic is held on red in-any case. While this optimises junction performance for vehicles, it is a pain in the neck for pedestrians who have to wait for a complete cycle of the lights to make each short hop from one cattle-pen to the next.

I can't remember now without checking back which word you used, but what I understood you to mean was that you arrive at the lights and if they're green you just ride across the junction in one movement; as opposed to having to stop and start again midway. I think that was pretty clear and the technical terminology is useful in other circumstances but a distractor here.

As for being overtaken by buses though, my experience is different to your description. Many bus routes have buses every minute or two (not all the same service but often many services follow one road for part of their route), bus speeds and loadings vary from place to place, as do stop intervals and of course cyclist speeds. If you can maintain a constant 20mph+ including uphill, you might very rarely get overtaken by buses, I guess. \OTOH I used to have a commute where uphill was the part on which I could pull away from the bus, as it was overloaded and struggled (more than me!) up the hill. Perhaps the stops were closer together on that part as well, I can't remember now.

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Re: Bus controlled traffic lights

Postby mjr » 19 Mar 2019, 4:39pm

Pete Owens wrote:As junctions become bigger more stages may be added for particular turning movements and islands put in to break up pedestrian movements (the shorter each pedestrian crossing is the less time is allocated for the crossing thus maximising the time allocated to vehicles - indeed also most pedestrian crossing can be slotted into stages where the motor traffic is held on red in-any case. While this optimises junction performance for vehicles, it is a pain in the neck for pedestrians who have to wait for a complete cycle of the lights to make each short hop from one cattle-pen to the next.

Yes, that's a pain and this is another way that having distinct high-quality cycleways is helpful for pedestrians because where junctions are getting rebuilt to allow cycleways to cross in single stages, the necessary extra lamp heads are often installed to stop left turners and enable the pedestrian crossings to become single-stage parallel with the cycleway, such as at https://mapstreetview.com/#uo154_-1q43_3l.a_-8i43

(Although a slow handclap for NCC for installing signal heads to hold left turners at https://mapstreetview.com/#vehwi_8lyu_7f.j_1e43 but then bizarrely still making the crossing multi-stage.)

At the moment, the main problem seems to be that highways departments often chicken out of reinstating the pedestrian crossing across the last arm of the junction where it was previously removed to give more % of the time to motorists.
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Re: Bus controlled traffic lights

Postby StephenW » 19 Mar 2019, 10:41pm

This may be of interest, especially the eighth paragraph:

https://bicycledutch.wordpress.com/2016 ... interview/