Crossing 'waiting' time

seank
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Crossing 'waiting' time

Postby seank » 2 Dec 2011, 3:55pm

we've been having a discussion re: the 'waiting' time forced on users of road crossing - the time from pressing the button to the crossing cycle starting. Questions;

- why do authourities set this at all, why not have immediate response to the button being pressed (disregarding the situation where there has been a recent crossing cycle)?
- I was once told by my local authourity that it was out of their hands, they had to follow national guidelines - is this true or can a local authourity decide to set a crossing how it likes?
- if it is so that authourities have to follow national guidelines who does govern the setup for crossings?

You do get the impression this 'waiting' time is just there to keep you in your place and remind you of your second class position relative to car users,

cheers, Sean

broadway
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Re: Crossing 'waiting' time

Postby broadway » 2 Dec 2011, 4:48pm

seank wrote: - I was once told by my local authourity that it was out of their hands, they had to follow national guidelines - is this true or can a local authourity decide to set a crossing how it likes?
- if it is so that authourities have to follow national guidelines who does govern the setup for crossings?


If they are guidelines they don't have to follow them as shown by the guidelines for the width of cycle lanes.

northstar
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Re: Crossing 'waiting' time

Postby northstar » 2 Dec 2011, 5:01pm

I'd probably say there are national guidelines, like tfl's "smoothing the traffic" flow policy.

Though if you press the button for horse riders here:

http://maps.google.co.uk/maps?q=robin+h ... CBQQ_AUoAg

It stops the vehicles quicker than pressing the pedestrian/cycle button...

Ironically it stops the other side almost instantly but you are still waiting to get to the middle - it would be much quicker for all concerned for it stop cars straight away and cross in one go.

Ron
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Re: Crossing 'waiting' time

Postby Ron » 2 Dec 2011, 7:20pm

This link should help you, see pages 9-11 and 17-21. I do not know if this is the most up to date information. http://www2.dft.gov.uk/pgr/roads/tpm/lt ... in4034.pdf

thirdcrank
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Re: Crossing 'waiting' time

Postby thirdcrank » 2 Dec 2011, 8:32pm

While waiting for somebody who knows about national guidelines to post, I think it's worth pointing out that there is a national ethos among highwaymen that if anybody is going to have to wait, it should be the people who they contemptuously dismiss as "peds." I see the stuff in Ron's link refers to "gap" changes and "forced" changes, presumably the latter is when the signals show STOP when traffic is actually passing, rather than when a gap is detected, which might mean that no vehicle was stopped at all, and any that were would be those who arrived after the signals had started to think about showing the green man.

To some extent, I can see the logic in this, as I know from experience gained many years ago standing in a box in the middle of a junction and waving my arms about, the delays come during the period when everything is stopped. Be that as it may, there are light-controlled pedestrian crossings which do not recognise even quite prolonged gaps in traffic. There is one quite near here which I have never timed, but if I wait for a safe gap in the traffic ie nothing in sight, press the button and go without waiting for the green man, I can be well over a hundred yards up the road, even at my geriatric strolling pace, before the traffic gets a red light. As I said, the problem is the ethos which can generally twist any guidelines to suit.

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Alex L
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Re: Crossing 'waiting' time

Postby Alex L » 2 Dec 2011, 8:33pm

There is one on my commute to uni that acts normal in the day. However at night it changes to amber in seconds every time. Probably due to the large amount of drunken students at night ;)

PRL
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Re: Crossing 'waiting' time

Postby PRL » 2 Dec 2011, 10:18pm

Ron wrote:This link should help you, see pages 9-11 and 17-21. I do not know if this is the most up to date information. http://www2.dft.gov.uk/pgr/roads/tpm/lt ... in4034.pdf


As I read it (and clear English it isn't ) that puts a gratuitous 20-60s wait after the pedestrian has pushed a button before the system thinks of letting them across. That will teach them not to be an important person in a car ! :evil:

SilverBadge
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Re: Crossing 'waiting' time

Postby SilverBadge » 3 Dec 2011, 10:59am

PRL wrote:
Ron wrote:This link should help you, see pages 9-11 and 17-21. I do not know if this is the most up to date information. http://www2.dft.gov.uk/pgr/roads/tpm/lt ... in4034.pdf


As I read it (and clear English it isn't ) that puts a gratuitous 20-60s wait after the pedestrian has pushed a button before the system thinks of letting them across. That will teach them not to be an important person in a car ! :evil:
Without having read it, I think it is reasonable for there to be a minimum period of time between successive operations, but once that time has expired I can't see any reason for operation to be near instantaneous. Is there a presumption that pedestrians will just "push and go" and should therefore always have to wait a short period?

snibgo
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Re: Crossing 'waiting' time

Postby snibgo » 3 Dec 2011, 11:29am

After reading the doument in Ron's link a few times, I think I now understand it.

The difficulty for maximising road flow at crossings is that the minumum time for road traffic on green is quite short -- "normally 6 seconds" for Toucans. Compare this to the total time of around 20 seconds for non-green.

When a pedestrian or cyclist wants to cross, the lights will start to change when the minimum has expired and either (a) there is a gap in the road traffic or (b) the maximum green time has expired. This maximum is normally "40 seconds or less", but could be up to 60 seconds. For slow roads, it is timed from when the green light started. For fast roads, it starts when the pedestrian or cyclist wants to cross.

On busy roads this scheme makes crossers wait. This is good for maximising road flow because (among other reasons) it gives a chance for other pedestrians and cyclists to catch up, so they all cross in a single bunch, rather than all crossing separately with their own separate light changes.

I emphasise this is good for maximising road flow. Alternative objectives are possible.

thirdcrank
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Re: Crossing 'waiting' time

Postby thirdcrank » 3 Dec 2011, 11:49am

SilverBadge wrote: ... Without having read it, I think it is reasonable for there to be a minimum period of time between successive operations ...
On what basis do you say that?

The pedestrian waiting time before a steady stream of traffic is stopped by a "forced" red is a matter of policy (although it is dressed up as science.) The present policy is that traffic should be given what might be called a good run, as the alternative would be the risk of substantial congestion.

OTOH, there seems to be no such reason for prolonged delays before a "gap" red. ie nothing coming so STOP signal is just ensuring that pedestrians using the crossing are protected from traffic which arrives when they are on the way over. The obvious time that this is particularly relevant is when a road has both busy and relatively quiet periods, the latter being usually at night. Imagine an empty road, late evening. A pedestrian arrives, pushes the button and doesn't get an almost immediate green man, or at least, the amber for traffic, indicating that the green man is getting his act together. Nothing coming so some will be tempted to cross, and the longer they have to wait for no obvious reason, the more pedestrians will be tempted to cross, rather than wait for a green man which may be this year, next year, sometime... Even if they get safely acroos before any traffic arrives, on older systems it's quite likely that when the green man appears for a pedestrian who did not wait, traffic will be stipped for no reason.

One result of what I'm saying has been the fitting of pedestrian detectors to ensure they are still there waiting when their turn eventually comes.

(snibgo got in before me.)

snibgo
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Re: Crossing 'waiting' time

Postby snibgo » 3 Dec 2011, 12:19pm

Thirdcrank's example of a pedestrian wanting to cross an empty road illustrates the situation when the objective should be inverted: we want to minimise the delay to crossers (and maximise the flow at the crossing, which isn't exactly the same thing).

snibgo
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Re: Crossing 'waiting' time

Postby snibgo » 3 Dec 2011, 12:58pm

More than I ever wanted to know about Puffins (Pedestrian User Friendly INtelligent) here: http://webarchive.nationalarchives.gov. ... iceguide01

And heaps of other DfT bumf about crossings: http://www2.dft.gov.uk/pgr/roads/tpm/tal/

thirdcrank
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Re: Crossing 'waiting' time

Postby thirdcrank » 3 Dec 2011, 3:50pm

I think this is one of those examples where my economic model gives a good analysis. The ability to move freely using the road network is a good, in an economic sense. There isn't enough of this to go round so we get congestion. Traffic signs such as traffic lights and STOP signs, distribute this good by a form of rationing, rather than letting the survival of the fittest prevail. The various forms of pedestrian crossing just distribute a share to pedestrians. The Zebra is worth thinking about because it offers pedestrians an immediate slice of the cake just so long as they are prepared to chance it by stepping off the kerb to claim their right of precedence, in the face of some drivers who would prefer every man for himself in their big powerful motor vehicles. Light controlled signals, in the various zoological incarnations, all follow the basic rationing system, but what we are talking about there is "peds" being kept waiting for their crumbs while the big misters have eaten to their full and then waiting even longer, just in case any more big misters may come along.

Vorpal
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Re: Crossing 'waiting' time

Postby Vorpal » 3 Dec 2011, 5:22pm

I believe the current guidance is at:

http://www2.dft.gov.uk/pgr/roads/tpm/ta ... co4102.pdf
http://www2.dft.gov.uk/pgr/roads/tpm/ta ... co4103.pdf
http://www2.dft.gov.uk/pgr/roads/tpm/ta ... co4104.pdf
http://www2.dft.gov.uk/pgr/roads/tpm/ta ... co4105.pdf

The fourth one has most of the information about timing. There have been a number of studies about the factors influencing safety & the balance between pedestrian crossing time, capacity, and driver disobedience.

TRL published a literature review & summary in 2006 http://www.pedestrians-int.org/content/18/222006_p.pdf

I think there have been a couple of more recent studies, but I didn't find them with a quick google. If I find them later, I'll add them to this thread.
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PRL
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Re: Crossing 'waiting' time

Postby PRL » 3 Dec 2011, 10:07pm

[quote="SilverBadge" I think it is reasonable for there to be a minimum period of time between successive operations, but once that time has expired I can't see any reason for operation to be near instantaneous. Is there a presumption that pedestrians will just "push and go" and should therefore always have to wait a short period?[/quote]

The system seems to require a waiting time even if there had been no pedestrians crossing for some time - hence my "gratuitous" .