Traffic Signal Right Turn Confusion

[hughster]

The sense I get is that a red arrow could communicate a subtly (but perhaps crucially) different meaning to a red ball with a black arrow, i.e. "you must stop if you're going in the indicated direction" vs "stop, exactly like a normal red ball, but this is the indicated direction this signal head will allow you to go in when it changes".

Compare red arrows to pedestrian/cyclist signals showing a red man/cycle symbol aspect, which mean "you must stop if you are a pedestrian/cyclist [and this does not apply to anyone else]". The "you must stop IF" meaning is what you want in those cases but might not want with full signals.

Also, a red arrow is used in other jurisdictions as a negative exception to a green ball, whereas right now UK signals only use a green arrow as a positive exception to a red ball, and a lot of setups would need to be reworked to take advantage of this.

(Edit: having checked the regs for some of the countries that use black arrows, e.g. DE/CH/PL/SE, they all say that a red ball with a black arrow does mean "you must stop if you're going in the indicated direction", so no subtly different meaning. But it does seem that a red arrow would be clearer if that's what you want it to mean, especially if shown next to a green ball. E.g. here in Geneva: as you approach it looks like conflicting signals but once you're at the stop line you can see the arrow outline on the red: https://www.google.co.uk/maps/@46.19941 ... 312!8i6656)

[Peter Freeman]

The sense I get is that a red arrow could communicate a subtly (but perhaps crucially) different meaning to a red ball with a black arrow, i.e. "you must stop if you're going in the indicated direction" vs "stop, exactly like a normal red ball, but this is the indicated direction this signal head will allow you to go in when it changes".

Uh?
In AU, a red arrow certainly means "you must stop if you want to go in the indicated direction". It may be accompanied simultaneously, usually side-by-side, by either a red ball or a green ball, and the meaning is perfectly obvious. It also carries the meaning that you'll get a green arrow allowing you to go when it changes, even though the accompanying ball, which will apply to all other directions, may simultaneously be either red or green.

Compare red arrows to pedestrian/cyclist signals showing a red man/cycle symbol aspect, which mean "you must stop if you are a pedestrian/cyclist [and this does not apply to anyone else]". The "you must stop IF" meaning is what you want in those cases but might not want with full signals.

Uh?
Following your logic with the red pedestrian+cycle picture, the red arrow would then mean "you must stop if you are an arrow [and this does not apply to anyone else]" ... !?

Also, a red arrow is used in other jurisdictions as a negative exception to a green ball, whereas right now UK signals only use a green arrow as a positive exception to a red ball, and a lot of setups would need to be reworked to take advantage of this.

In our AU system, you're right: a red arrow is used as a negative exception to a green ball. But our green arrow is used as a positive exception to a red ball, same as yours. They're not in contradiction, and an immediate re-work would not be necessary.

In summary, the difference UK versus AU is simply the shape, not the colour, of the light. You use red and amber balls where we use red and amber arrows. I see no sense in black arrows.

[hughster]

Following your logic with the red pedestrian+cycle picture, the red arrow would then mean "you must stop if you are an arrow [and this does not apply to anyone else]" ... !?

My thinking was more that a red ped/cycle symbol indicates a "stop IF" rule for certain traffic only, similar to how a red arrow would create a "stop IF" rule for traffic heading in that direction only. I agree that that could be useful, but others might think it preferable to keep red as a general "stop".

In our AU system, you're right: a red arrow is used as a negative exception to a green ball. But our green arrow is used as a positive exception to a red ball, same as yours. They're not in contradiction, and an immediate re-work would not be necessary.

The reworking I had in mind was for situations such as those where, with a single stop line, you wanted to hold the left turn lane on red but show a green ball (i.e. giving way to oncoming traffic) for straight ahead and right. Currently you can't do this in the UK, but with a red arrow, you could, so you might want to rework your junction to take advantage of that new option.

[swissferry]

I think these lights are a terrible design. Would have thought one set with a left filter would be simpler and safer. Or if sets for turning left and right are required then having the far side ones on the same pole would help. Both left and right sets change at the same time unless the filter arrow is on for traffic turning into the street in which case the left set change to green first. Have seen a couple of near misses because cars turning right start moving when the left set change to red/amber.

[WhiteBlueRed]

I think these lights are a terrible design. Would have thought one set with a left filter would be simpler and safer. Or if sets for turning left and right are required then having the far side ones on the same pole would help. Both left and right sets change at the same time unless the filter arrow is on for traffic turning into the street in which case the left set change to green first. Have seen a couple of near misses because cars turning right start moving when the left set change to red/amber.

I think adding louvres to the left traffic light could solve that problem.

[traffic-light-man]

I think these lights are a terrible design. Would have thought one set with a left filter would be simpler and safer. Or if sets for turning left and right are required then having the far side ones on the same pole would help. Both left and right sets change at the same time unless the filter arrow is on for traffic turning into the street in which case the left set change to green first. Have seen a couple of near misses because cars turning right start moving when the left set change to red/amber.

I'd love to know the design idea behind that one, it seems like such an odd choice, but I do wonder if the designer was thinking the polar opposite to what we're saying here, i.e. that separating them out will make it more obvious what's going on. IMO, it's just a waste of a pole, ducting and cable more than anything else.

Using a full phase rather than a filter is more efficient because it can be terminated without needing to drag the associated full phase in to cancel it, which means running an unnecessary set of intergreeens and phase minimums. It doesn't matter if it's always likely to have a demand for the associated phase (i.e., on a 'main' road), but on a side road it's often wasteful to use a filter for that reason.

Of course there are plenty of places the use closing ambers just for filter and indicative arrows (including Northern Ireland for the latter) which avoids this issue, which is something else that I believe just makes sense. Particularly if it used an amber arrow.

[AndyB]

NI is using fewer closing ambers on indicative arrows than it used to, but they were only ever used where there was going to be no demand from the side road and it was necessary to allow traffic from the opposite direction to start again.

We have an example of the OP at Knock Road/Upper Newtownards Road in Belfast. The arrows both ways are because there is enough demand for the right turn city bound to also come up as an exit arrow at the end of the next phase.

[MotorwayGuy]

Then you have the opposite problem, where the main movements are on filters, such as this location, which results in people missing the green arrows and sitting there. There used to be two more like this on the same road (here and here which were Mellors to make things even worse), but they have been replaced with roundabouts.

[wallmeerkat]

Then you have the opposite problem, where the main movements are on filters which results in people missing the green arrows and sitting there.

I've seen that on a retail park in the outskirts of Belfast - https://www.google.com/maps/@54.6547575 ... 384!8i8192, people focus on the red and miss the green arrow until they hear a friendly toot.

Conversely the Saintfield Road on the other end of the city is crying out for a turning lane and right turn filter - https://www.google.com/maps/@54.5395289 ... 384!8i8192 - you can see the black Nissan in the outside lane indicating and the BMW SUV has merged into the left lane to go straight ahead. The worst about it is as it is a busy road right turning traffic will sit for ages, but the lights are set up weirdly such that even when the light is red here, it is not safe to turn right if you're in the middle of the junction as they remain green for oncoming traffic for a short while, as you can see on SV on approach coming the other direction, green light but the other side is sitting on a red - https://www.google.com/maps/@54.5402489 ... 384!8i8192

[MotorwayGuy]

Then you have the opposite problem, where the main movements are on filters which results in people missing the green arrows and sitting there.

I've seen that on a retail park in the outskirts of Belfast - https://www.google.com/maps/@54.6547575 ... 384!8i8192, people focus on the red and miss the green arrow until they hear a friendly toot.

Conversely the Saintfield Road on the other end of the city is crying out for a turning lane and right turn filter - https://www.google.com/maps/@54.5395289 ... 384!8i8192 - you can see the black Nissan in the outside lane indicating and the BMW SUV has merged into the left lane to go straight ahead. The worst about it is as it is a busy road right turning traffic will sit for ages, but the lights are set up weirdly such that even when the light is red here, it is not safe to turn right if you're in the middle of the junction as they remain green for oncoming traffic for a short while, as you can see on SV on approach coming the other direction, green light but the other side is sitting on a red - https://www.google.com/maps/@54.5402489 ... 384!8i8192

The reason that has an early cut-off is so traffic doesn't fill the space between the junctions whilst the right turn filter is active for oncoming traffic, which would give traffic coming out of the side turning nowhere to go. Normally in these situations a far-side secondary shouldn't be used for the reason you described, that when traffic waiting to turn sees their signal go to red, there is an assumption that oncoming traffic will have the same. The only way around this would be to have separate right-turn phases for each direction and convert the offside lanes to right turn only.

[pjr10th]

Similar situation to that one in Hamilton - a full green arrow substituting for a left turn filter. The right turn light is never on without the left turn light. It seems a filter arrow would be better.

https://maps.app.goo.gl/npKGZu8ygya2pkmx8

The following is the same, except the lights are never on without one another (they go red at the same time too). Seems bizarre to signal them separately. I don't even think at night the junction operates on-demand for left turners. Similarly with the signals in the middle of the junction, I've only ever seen people stopped at the red if they ran the end of the previous amber a bit riskily. Further confusingly, the opposing flow goes at the same time with the same left right arrow. Predictably drivers turning right are unaware.

https://maps.app.goo.gl/LdUVEX2L4wzDj5Lc6

Given the lack of red-amber at the lights, this might be less of a safety problem. Left filter arrows don't really seem to exist in Jersey anyway, I've certainly never seen one, and only a handful of right filter arrows exist too (most right turns are protected or very uncommon).

[AndyB]

Then you have the opposite problem, where the main movements are on filters which results in people missing the green arrows and sitting there.

I've seen that on a retail park in the outskirts of Belfast - https://www.google.com/maps/@54.6547575 ... 384!8i8192, people focus on the red and miss the green arrow until they hear a friendly toot.

Conversely the Saintfield Road on the other end of the city is crying out for a turning lane and right turn filter - https://www.google.com/maps/@54.5395289 ... 384!8i8192 - you can see the black Nissan in the outside lane indicating and the BMW SUV has merged into the left lane to go straight ahead. The worst about it is as it is a busy road right turning traffic will sit for ages, but the lights are set up weirdly such that even when the light is red here, it is not safe to turn right if you're in the middle of the junction as they remain green for oncoming traffic for a short while, as you can see on SV on approach coming the other direction, green light but the other side is sitting on a red - https://www.google.com/maps/@54.5402489 ... 384!8i8192

Funny you should post that. I drove up that way two weeks ago, and they’ve just completed a scheme to do exactly that to that junction.

[wallmeerkat]

Funny you should post that. I drove up that way two weeks ago, and they’ve just completed a scheme to do exactly that to that junction.

Saintfield Road - Knockbracken Road got a turning lane? Was up that way recently and it hadn't changed? Or right turn filter? (I was travelling Knockbracken to Saintfield Road so would've missed this)

[AndyB]

Sorry, the maps link took me to the junction of Saintfield Road/Church Road Carryduff. No danger of much happening at Knockbracken, I don’t think.

[AndyB]

Ah, no, it was me - the link was correct, I just thought it was Carryduff.

I use Longwood Road from time to time, because my office (when I’m in it) is round the corner, but usually I come down Mill Road instead. I usually don’t have any issues when I do use it though.

[traffic-light-man]

The only way around this would be to have separate right-turn phases for each direction and convert the offside lanes to right turn only.

Or do a late start indicative arrow with a closely associated secondary...

Similar situation to that one in Hamilton - a full green arrow substituting for a left turn filter. The right turn light is never on without the left turn light. It seems a filter arrow would be better.

Except with this arrangement you can close down the left turn without having to run the right turn if there's no demand for it. If it were a filter, you'd need to run the full green to clear the filter, so you'd have to run two extra sets of intergreens and a min green for no reason. This is why filters on 'side roads' are not the most efficient solution.

[pjr10th]

Similar situation to that one in Hamilton - a full green arrow substituting for a left turn filter. The right turn light is never on without the left turn light. It seems a filter arrow would be better.

Except with this arrangement you can close down the left turn without having to run the right turn if there's no demand for it. If it were a filter, you'd need to run the full green to clear the filter, so you'd have to run two extra sets of intergreens and a min green for no reason. This is why filters on 'side roads' are not the most efficient solution.

I know but the junction seems to treat it like a filter anyway. I've sat at the red at night as someone turns right over me. The full green arrow comes on at the same time. But then it without fail always then gives the side road the right arrow before cancelling, even for just a couple of seconds.

[traffic-light-man]

I know but the junction seems to treat it like a filter anyway. I've sat at the red at night as someone turns right over me. The full green arrow comes on at the same time. But then it without fail always then gives the side road the right arrow before cancelling, even for just a couple of seconds.

Ah, I see. This one has similar symptoms, and it could be for similar reasons. If the only demand is for the right turn off Millennium Way, the left turn on Blackburn Road will show and then shut down with the Millennium Way right turn, perhaps as you'd expect. The issues arise with Blackburn Road, because the X detector is located prior to the lanes splitting. As a result, even if a driver makes use of the left turn while it's on 'early', they've already passed over the X and so have also put a demand in for the right turn as well which renders the whole setup somewhat pointless as the right turn then has to run for no reason just because it's seen a demand.