Botched Traffic Signals

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jcpren
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Re: Botched Traffic Signals

Post by jcpren » Thu Dec 24, 2015 11:57

Are they aimed slightly differently? One for the car waiting at the stop line, and one for cars approaching from the distance?
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Re: Botched Traffic Signals

Post by michael769 » Thu Dec 24, 2015 12:41

jcpren wrote:Are they aimed slightly differently? One for the car waiting at the stop line, and one for cars approaching from the distance?
For the A57 and Liverpool examples I suspect you are correct.

The Barking onelooks to be due to differing approach angles - vehicles in the right hand lane approach at what looks like a 45 degree angle compared to traffic in other lanes - and I suspect they would struggle to see the signals on approach without the extra head which is pointed in their direction.
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Re: Botched Traffic Signals

Post by jcpren » Sat Jan 02, 2016 00:11

Can anyone explain the existence of the "straight on" green filter arrow at this junction? It always comes on a few seconds before the main green.

https://goo.gl/maps/uMb4ccrkdkF2

Ignoring the pedantic point that both lanes have to go straight on at this stop line, and that the right hand lane only turns off to the right a bit further on, is there any reason why the left-hand lane should get a head start? There are no pedestrian facilities to complicate things, and the only conflicting traffic (which comes from the right) is identical for both lanes - and always stopped before the filter comes on. The next conflicting point for the right turners is separately phased, albeit part of the same set of signals. Also, the filter pre-dates the cycle lane/advanced stop line, so it's nothing to do with that.
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Re: Botched Traffic Signals

Post by michael769 » Sat Jan 02, 2016 14:41

It will have something to do with how right turn traffic interacts with the next set of lights and any traffic which may queue there.

Couple of throughts:

Have a look at this view. Notice the space between the stop line and the box junction where a car can get "stuck" if there is a queue at the next set of lights.

There is potential for for conflict between any car so caught and traffic being shown the green light in your view - as both will technically have equal priority - so it may be safer to hold traffic back to allow a car from the right to clear the junction. As a side benefit allowing any queue for the next set of lights to get moving before traffic is released will reduce the chances that traffic will move off only to have to stop again - something that wastes fuel and increases pollution.

The ahead direction has a free flow and probably won't get queues so there's no reason to hold them up in the same way.

The above assumes that the next set of lights get a green when (or just before) the filter comes on.

If they don't my other thought is that it would be to reduce the number of vehicles which get through to queue there (and potentially block the box junction).
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Re: Botched Traffic Signals

Post by jcpren » Sat Jan 02, 2016 16:14

Thanks Michael, that makes sense. I'll keep an eye on the next set of lights the next time I'm passing through, and see which it is.

I suspect the latter - any cars coming from the right, and then wanting to turn right again, will actually be doubling back to where they came, as the junction only has three arms. It can't be *that* popular a movement, so I would have thought it more likely that cars coming from my original point of view would block the space between the lights, rather than cars coming from the right.
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Re: Botched Traffic Signals

Post by jcpren » Sun Jan 03, 2016 10:52

Another thought: strictly speaking, would you be entitled in law to proceed in the right hand lane as soon as the filter arrow came on, since you're actually going straight ahead at that point? If I remember correctly, a filter arrow allows you to proceed in the direction shown "regardless of what other signals are showing"...
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Re: Botched Traffic Signals

Post by Andy33gmail » Sun Jan 03, 2016 10:59

Any reason you couldn't do so in the right hand lane? The green arrow mandates a direction, not a lane.

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Re: Botched Traffic Signals

Post by jcpren » Sun Jan 03, 2016 11:03

Andy33gmail wrote:Any reason you couldn't do so in the right hand lane? The green arrow mandates a direction, not a lane.
Well, because it's not what they had in mind. The *only* direction is straight on - but would the law agree if it came to an argument?
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Re: Botched Traffic Signals

Post by Andy33gmail » Sun Jan 03, 2016 12:24

The police are missing an opportunity to park up a scamera van and do anyone proceeds in lane 2 while the right arrow is on green and the ahead arrow is off for driving otherwise in accordance with the signals

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Re: Botched Traffic Signals

Post by jcpren » Sun Jan 03, 2016 14:22

It's a green ball that comes on rather than a right arrow, so I'm afraid not!
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Re: Botched Traffic Signals

Post by michael769 » Sun Jan 03, 2016 14:42

jcpren wrote:
Andy33gmail wrote:Any reason you couldn't do so in the right hand lane? The green arrow mandates a direction, not a lane.
Well, because it's not what they had in mind. The *only* direction is straight on - but would the law agree if it came to an argument?
It's not something I'd want to test. I would agree the arrangement is rather iffy.
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Re: Botched Traffic Signals

Post by jcpren » Sun Jan 03, 2016 16:28

It looks like quite an old installation, so it will be interesting to see if it gets a rethink when the signals are replaced.
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Re: Botched Traffic Signals

Post by scynthius726 » Sun Jan 03, 2016 18:15

I bet you're not surprised that I also noticed this one, John! :wink:

Filter arrows at signalised roundabouts are unusual, but not unheard of - here is another example. At the M77 example, though, the filter is on for a relatively long time, at the same time as traffic from the northbound motorway off-slip has a green. The filter arrangement here makes sense because if traffic on Leggatston Drive were given a full green, they would merely have to stop again at the next stopline.

There was originally going to be a left filter at Mavor Roundabout in East Kilbride ("PC World Roundabout") - I'm not sure why that was rescinded.

Back to the Cambuslang Road, site, however, you're right that it's a strange one. I suspect a previous configuration of the signals may have been somewhat simpler, with the filter arrow included, but no phase delays. Phase delays could then have been added at a later date but it was felt that there was no harm in retaining the filter arrow.
Last edited by scynthius726 on Sun Jan 03, 2016 19:20, edited 1 time in total.
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Re: Botched Traffic Signals

Post by Glen » Sun Jan 03, 2016 19:18

There's also one in Aberdeen with a left filter on a roundabout.
The only difference it make is that right turning traffic doesn't have to move forward to a red signal at the next stop line, the junction would still work the same if it went straight to green for both lanes.

https://goo.gl/maps/7Pj5HTxx3yF2

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Re: Botched Traffic Signals

Post by L.J.D » Sun Jan 03, 2016 21:37

Same here

Also further back another oddity here. A signal junction with one minor arm give way. It seems they had signals in because you can see the old stop line and the old NAL socket beside it. As to why they decided to remove them I couldn't say. I think it's because it's a minor small dead end road. Which begs the question why they installed it in first place because it's a relatively newish installation and before it had no signals at all. Just give way from the side roads.

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Re: Botched Traffic Signals

Post by traffic-light-man » Thu Jan 14, 2016 20:49

In an image on a Google image search, I noticed a strange set up. With a bit of investigative work, I tracked down the site.

Take a look at this installation. The extra aspects are advance cycle indications, but I don't understand why separate housings have been used. And somewhat more annoyingly, why put the nearsides (albeit toucans, despite the cycle facilities on the carriageway) in all-black housings, or is this something that's allowed now?
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Re: Botched Traffic Signals

Post by Andy33gmail » Fri Jan 15, 2016 10:58

I hate those new pedestrian light designs - I know there's a fallacious argument made for them in terms of safety - but I'm sure it's just to save the cost of a signal head(?)

Before, when crossing expediently you were encouraged to look at the lights on approach, and in doing so look at the entire road scene. Now you have to learn the signal timings and look at the car lights to get the same information.

But presumably "normal" people will now be looking at the signals without looking at the road, and are liable to walk in front of emergency vehicles / red light violators / slow vehicles who haven't cleared the junction.

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Re: Botched Traffic Signals

Post by L.J.D » Sun Jan 31, 2016 00:22

What's going on here!! I know it says emergency vehicles only but surely it makes the lights pointless I can't see emergency services waiting for them to change to green in an emergency. It just looks completely stupid. Surely a give way would just be better.

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Re: Botched Traffic Signals

Post by jcpren » Sun Jan 31, 2016 07:39

L.J.D wrote:What's going on here!! I know it says emergency vehicles only but surely it makes the lights pointless I can't see emergency services waiting for them to change to green in an emergency. It just looks completely stupid. Surely a give way would just be better.
Maybe emergency crews can trigger the lights to change, but a red light at all other times (or even permanently if no such trigger exists) acts as an additional deterrent to all other drivers? Just a guess...
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Re: Botched Traffic Signals

Post by Glen » Sun Jan 31, 2016 16:26

L.J.D wrote:What's going on here!! I know it says emergency vehicles only but surely it makes the lights pointless I can't see emergency services waiting for them to change to green in an emergency. It just looks completely stupid. Surely a give way would just be better.
It's right next to the fire station.
I expect there will be a button in the fire station to trigger the signals to give priority to fire appliances.

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