Nearside indicators: Why are they a thing?

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WHBM
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Re: Nearside indicators: Why are they a thing?

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WhiteBlueRed wrote: Sat Apr 30, 2022 11:23
WHBM wrote: Fri Apr 29, 2022 21:56 Just as an aside, is there a reason WHY countdowns are incompatible with nearsides ?
Probably because at most nearside installations, the pedestrian-to-vehicle intergreen is variable. Also, a countdown mainly exists to let crossing pedestrians know how much time they have to cross, and with nearside indicators (defeating the main purpose) and vehicle-actuated stages, you can't really know for sure how long it is until the green man appears.
That's not really the case in central London, where the bulk of the countdowns I have encountered seem to be, where TfL, who manage all traffic signals, have pretty much abandoned vehicle actuated stages because they are felt incompatible with bicycles which cannot actuate.
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Re: Nearside indicators: Why are they a thing?

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WHBM wrote: Sat Apr 30, 2022 11:53
WhiteBlueRed wrote: Sat Apr 30, 2022 11:23
WHBM wrote: Fri Apr 29, 2022 21:56 Just as an aside, is there a reason WHY countdowns are incompatible with nearsides ?
Probably because at most nearside installations, the pedestrian-to-vehicle intergreen is variable. Also, a countdown mainly exists to let crossing pedestrians know how much time they have to cross, and with nearside indicators (defeating the main purpose) and vehicle-actuated stages, you can't really know for sure how long it is until the green man appears.
That's not really the case in central London, where the bulk of the countdowns I have encountered seem to be, where TfL, who manage all traffic signals, have pretty much abandoned vehicle actuated stages because they are felt incompatible with bicycles which cannot actuate.
I'm sure they use SCOOT, so I guess it's not a big of a loss in having semi-fixed stages. Then in theory, countdowns until the green man appears should be possible. Maybe it could be an additional light above/below/on the side of the indicator, like countdowns originally were here in Russia, before they started to be embedded into the signal itself.
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RichardA35
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Re: Nearside indicators: Why are they a thing?

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Given the throughput of pedestrians is often the largest flow for some junctions in central London, it strikes me that the pedestrian stage should perhaps be the default with the motor vehicles given the subordinate position and the countdown timer.
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Re: Nearside indicators: Why are they a thing?

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WhiteBlueRed wrote: Sat Apr 30, 2022 11:59I'm sure they use SCOOT, so I guess it's not a big of a loss in having semi-fixed stages.
Some of central London still runs 'proper' UTC fixed time as well, rather than SCOOT. I'm not sure what is meant by semi-fixed, but SCOOT stage times are not fixed in length unless they're set up to be. You wouldn't normally set a standard vehicular movement as a fixed time stage length. London also has some instances of Pedestrian SCOOT, too.
WhiteBlueRed wrote: Sat Apr 30, 2022 11:59Then in theory, countdowns until the green man appears should be possible.
Most of the GLOSA trial sites are using SCOOT sites which are working in isolation, just because the stage change data can be predicted and fed back in time for GLOSA to actually display the information, so feeding that information to a countdown isn't inconceivable. The problem is that SCOOT working on isolated sites like those can be incredibly inefficient.

The other thing to note with UTC fixed time and SCOOT is that any demand dependent stages give their time away to other stages if they're not demanded, so until the demand has been confirmed just before the stage change point, the length of that stage isn't yet known. So unless the system is setup to drive every stage in every cycle, there's still an unpredictability factor at play.

SCOOT wouldn't be a blanket solution though even for London, TfL will still have plenty of sites which run on VA and ped crossings which run on their own timings. I'm not sure applying SCOOT where there's no genuine benefit for anyone, particularly to sites with pedestrian facilities, is the right solution just in order to get a countdown timer to work.

I'd still like to know how the Dutch drive their countdowns, particularly the non-numeric ones where the speed of the countdown varies depending on the actuation. They're obviously driven directly by an output from the controller. In my experience, it looks as though they tend to start counting down at a predictable point in the cycle, but then once the stage change decision has been made, they speed up to match the time from the stage change decision point until the green appears. I'm fairly sure there's more to them than that, though, particularly given how Dutch 'staging' works!
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Re: Nearside indicators: Why are they a thing?

Post by Al__S »

The ideal (and probably not, in the grand scheme of things, massively more expensive) would be both near and far side indicators in my opinion.

Oh, and installing signals that are fully reactive and prioritise the movement of the most people most quickly
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traffic-light-man
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Re: Nearside indicators: Why are they a thing?

Post by traffic-light-man »

Al__S wrote: Sun May 01, 2022 09:42 The ideal (and probably not, in the grand scheme of things, massively more expensive) would be both near and far side indicators in my opinion.

Oh, and installing signals that are fully reactive and prioritise the movement of the most people most quickly
The nearside/farside hybrid solution has been seen in several places, and indeed is (or at least, was) standard on the Isle of Man.

This is one of the most prominent I can think of, though of course this crossing is non-standard in just about every way.

As for the fully reactive signals, that's not (IMV) difficult for us to do here in the UK either. It just involves political will, like many of the active travel scenarios, but unfortunately that is still a work in progress for a lot of the UK.
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Re: Nearside indicators: Why are they a thing?

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traffic-light-man wrote: Sun May 01, 2022 09:25
WhiteBlueRed wrote: Sat Apr 30, 2022 11:59I'm sure they use SCOOT, so I guess it's not a big of a loss in having semi-fixed stages.
Some of central London still runs 'proper' UTC fixed time as well, rather than SCOOT. I'm not sure what is meant by semi-fixed, but SCOOT stage times are not fixed in length unless they're set up to be.
By "semi-fixed" I mean stages where the green time can vary, but slower than a VA stage, which is what SCOOT is.
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Gareth
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Re: Nearside indicators: Why are they a thing?

Post by Gareth »

Surely, we never have countdown timers with nearside indicators because you simply can't see them anymore, once you've started crossing the road, rendering them pointless.

As for a hybrid farside/nearside, we did kind of have that anyway with the WAIT light on the push button, although it doubles as a "call recorded" indicator. A reform could be to have the WAIT always lit when the green man is unlit and have the button itself illuminate when the button is pressed.
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Re: Nearside indicators: Why are they a thing?

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RichardA35 wrote: Sat Apr 30, 2022 14:07 Given the throughput of pedestrians is often the largest flow for some junctions in central London, it strikes me that the pedestrian stage should perhaps be the default with the motor vehicles given the subordinate position and the countdown timer.
This is maybe a position of those who only periodically visit, and see little other than the crossings of Trafalgar Square or Oxford Street, but there are of course a vast number of signalled junctions where this is not true.

Motor vehicles already have the subordinate position, as there are a large number of junction arms where vehicles do not get through on the first green, and it takes multiple cycles of the lights to do so. I've never known a ped facility, at the same junctions or elsewhere, where you can't get over at the first stage.
Gareth wrote: Sun May 01, 2022 19:55 Surely, we never have countdown timers with nearside indicators because you simply can't see them anymore, once you've started crossing the road, rendering them pointless.
Not the case in London, where you have a countdown, sometimes seemingly over-lengthy, to zero, then followed by the full blank display as it used to have for crossing clearance. It seems the countdown is to the START of the clearance stage.

Take this one here I am very familiar with, the right turn from The Embankment into Horse Guards Avenue.

https://www.google.com/maps/@51.5048148 ... 384!8i8192

This is exactly as I describe, gives a right turn green of 8 seconds only. Oncoming left turn is prohibited. Prior stage is pedestrian green across Horse Guards, which has hardly any pedestrian traffic, the modal average pedestrians per stage must be zero. Yet it has this huge pedestrian countdown and then clearance time.
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Re: Nearside indicators: Why are they a thing?

Post by traffic-light-man »

I've never seen a countdown followed by a blackout. The countdowns replace the blackout, that's their purpose as originally proposed by TfL and now included in TSRGD.

In fact, the aspects themselves take a feed off both the red and the green pedestrian aspects and then simply display the difference between the green extinguishing and the red illuminating after two cycles of 'learning' that difference. They're not driven by the controller at all.

If there's a countdown followed by a blackout I'd suggest there's something is wrong and report it to TfL.
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Re: Nearside indicators: Why are they a thing?

Post by Gareth »

Also, I was talking about why you don't have them with nearsides.
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