poser for the weekend .. Traffic Lights

Davidth88

Hi

After my poser about the port tunnel , that got people talking , another one for you all.

What is this countries obsession with traffic lights ?

Increasingly I see traffic lights appear on every junction , on minor junctions, on major junctions, on roundabouts FFS ! and everywhere.

I have see perfectly good roundabouts that worked well be ripped out and be replaced with traffic lights.

I read recently that Kildare CC refused to put a mini roundabout into a junction which in my opinion would be perfect ( ie roughly equal flow between all the roads ) because ' they don't like roundabouts ' ( thats a quote ).

And even when traffic lights are fitted , there never seems to be any sensors fitted , so you end up sitting at a red light looking at an empty road because the stupid things are badly sequenced.

About a year ago all the lights in Maynooth failed for a couple of weeks, guess what , the world didn't end , and the traffic flowed much better. Local councillers were even heard saying perhaps they should be left off.

So what is it ? Do the local CC have shares on Traffic light manufacturers or something ?

paulm17781

The big problem is they are often in the wrong places or badly timed.

I can think of several spots in Dublin (city) that could do with lights and then some that are there for no reason. It really just seems to be looked at as "A set of lights" rather than a network of lights.

godtabh

Davidth88 wrote:

Hi

After my poser about the port tunnel , that got people talking , another one for you all.

What is this countries obsession with traffic lights ?

Increasingly I see traffic lights appear on every junction , on minor junctions, on major junctions, on roundabouts FFS ! and everywhere.

I have see perfectly good roundabouts that worked well be ripped out and be replaced with traffic lights.

I read recently that Kildare CC refused to put a mini roundabout into a junction which in my opinion would be perfect ( ie roughly equal flow between all the roads ) because ' they don't like roundabouts ' ( thats a quote ).

And even when traffic lights are fitted , there never seems to be any sensors fitted , so you end up sitting at a red light looking at an empty road because the stupid things are badly sequenced.

About a year ago all the lights in Maynooth failed for a couple of weeks, guess what , the world didn't end , and the traffic flowed much better. Local councillers were even heard saying perhaps they should be left off.

So what is it ? Do the local CC have shares on Traffic light manufacturers or something ?

Traffic lights when modelled correctly and set up correctly are an effective way of controlling traffic flows.

DDC use the SCATS system that monitors the city as a whole and adjusts the timings accordingly. DLRCC hard handing over allot of their junctions to DCC to make the junctions more efficient.

Proper traffic modelling can add up to 15% efficiency to traffic flows.

Zoney

When roundabouts were the rage, there were plenty put in at locations where junctions would have been better managed by traffic lights.

There are so many different types of junction, ways to install a roundabout (incl size) and setups of lights though, that it really comes down to do the council have a clue what they are doing or not, and do they have money (despite my cynicism of local authorities, actually they probably are stumped by money issues quite often). You'll find both perfect smoothly operating roundabout and signal-controlled junctions, and hideous inefficient roundabout and signal-controlled junctions with lengthy queues.

Add to that the fact that some (or many) junctions are just inadequate. Lights are usually needed at such locations to at least allow traffic to get through eventually (where a roundabout, or one without lights, might result in really bad queues disproportionately on one specific approach).

It seems to be only recently that there are more signal controlled junctions that are decently set up, with complex controller software/circuits managing the traffic flow on each approach using sensors. Older signal installations seem to just mainly be a fixed timing even if there are sensors installed - which doesn't make much sense (other than perhaps the council couldn't get more complex circuits to work in the controller box).

Having worked with industrial controllers and embedded software myself, I think there's no real need for traffic lights not to work very well indeed (or at least fairly) in any cases other than light traffic (where a roundabout or no lights is nice). However, it probably requires paying globs of money to Siemens or someone for decent controller kit and the maintanance thereof.

Anyways - I'm not an expert on traffic lights specifically, despite an interest in them, but I hope the above analysis is of some interest.

Sorry - just to add to that. Some traffic light setups are deliberately configured to be unfair where the main route is important and only a certain amount of traffic from a side-road can be accommodated. Not much else that can be done in such situations other than upgrade road infrastructure generally or distribute traffic differently e.g. with different directions signage or one-way system.

Calina

I venture to speculate that driver behaviour doesn't really help either though. Most light changes are accompanied by blatant red light breaking.

Davidth88

Traffic lights when modelled correctly and set up correctly are an effective way of controlling traffic flows.

But how often are they set up correctly, or even maintained because traffic flows do change .....

Even driving down the quays , how often do you get a green , then drive 50 yds to join a queue to another red light.......and people are then sitting at a green light because the cannot cross it .

Is SCATS an automated system of some kind where they sync the lights? If so they should ask for their money back What does it stand for , how does it work ??

Zoney... interesting and constructive stuff !

It just seems to me that it's a ' quick fix ' where the CC just stick in a set of lights and damn the consequences.

godtabh

Davidth88 wrote:

But how often are they set up correctly, or even maintained because traffic flows do change .....

Lots of county councils have consultants to advise them on this and give them the answers but these are used.

Alot of the traffic light software can adapt to changing vloumes of traffic. Lots of county councils dont use them.

On a side notes roundabouts arent used much in city centers due to the large land area required to achive high capacity

godtabh

Davidth88 wrote:

Is SCATS an automated system of some kind where they sync the lights? If so they should ask for their money back What does it stand for , how does it work ??

Yes. Its an Oz system but cant remeber what it stands for. Not all lights are on the system

markpb

Calina wrote:

I venture to speculate that driver behaviour doesn't really help either though. Most light changes are accompanied by blatant red light breaking.

This is an important point. A lot of junctions in Dublin seem to have deliberate 'dead-time' to allow for people running red lights.

godtabh

markpb wrote:

This is an important point. A lot of junctions in Dublin seem to have deliberate 'dead-time' to allow for people running red lights.

Its been awhile since i modelled anything but as far as I can remember there can be phases in the singles when all legs are red but this is usually to allow pedestrian crossings.

Davidth88

Actually I think that dead time may be for the poor pedestrians

Roundabouts do have their uses , but also their disadvantages , I remember clearly a mini roundabout being fitted in Harrow ( London ) that was then changed back to lights even though the roundabout helped traffic... because the pedestrians couldn't get across.

Kernsr , thats interesting stuff, perhaps we should have some sort of SLA with the CC's If only all the engineers responsible for these things were actually paid by performance/accountable.

Doesn't it defeat the whole purpose if not all the lights are on the system ?

If I had the answers of course I would be rich !

Calina

kearnsr wrote:

Its been awhile since i modelled anything but as far as I can remember there can be phases in the singles when all legs are red but this is usually to allow pedestrian crossings.

I don't think this is the case at the junction of the M1 and the M50/N32, however, and there is definitely dead time there...

Davidth88

I don't think this is the case at the junction of the M1 and the M50/N32, however, and there is definitely dead time there...

Actually a perfect example of ' why are there lights here ' .... driving from the airport to the motorway... on the roundabout.

There will NEVER ( or rarely ) be any traffic coming from the right , because there is no reason for anyone to be coming across there because all traffic would be going down to the a/port , but still we sit and wait like lemmings looking at an empty road for 1 -2 mins !

Crazy

godtabh

Davidth88 wrote:

Actually a perfect example of ' why are there lights here ' .... driving from the airport to the motorway... on the roundabout.

There will NEVER ( or rarely ) be any traffic coming from the right , because there is no reason for anyone to be coming across there because all traffic would be going down to the a/port , but still we sit and wait like lemmings looking at an empty road for 1 -2 mins !

Crazy

Traffic lights on roundabout dont work

Calina wrote:

I don't think this is the case at the junction of the M1 and the M50/N32, however, and there is definitely dead time there...

I dont know any one who would use dead time as it encourages breaking of red lights. Its bad design

daymobrew

Davidth88 wrote:

Is SCATS an automated system of some kind where they sync the lights? If so they should ask for their money back What does it stand for , how does it work ??

SCATS = Sydney Coordinated Adaptive Traffic System. No real info there.
I've read that it reverts to fixed timings when things get too busy.

Davidth88 wrote:

Actually a perfect example of ' why are there lights here ' .... driving from the airport to the motorway... on the roundabout.

There will NEVER ( or rarely ) be any traffic coming from the right , because there is no reason for anyone to be coming across there because all traffic would be going down to the a/port , but still we sit and wait like lemmings looking at an empty road for 1 -2 mins !

Traffic coming from the right could be heading for the shopping centre just south of Swords. Or to Cloghran. Or the pub between Cloghran and the roundabout.

paulm17781

kearnsr wrote:

I dont know any one who would use dead time as it encourages breaking of red lights. Its bad design

Have you forgotten what city / country this is?

godtabh

paulm17781 wrote:

Have you forgotten what city / country this is?

Whats your point? That the engineers cant do their jobs?

Wishbone Ash

Davidth88 wrote:

Increasingly I see traffic lights appear on every junction , on minor junctions, on major junctions, on roundabouts FFS !

Traffic lights may seem like a hinderence for the motorist who is travelling on a main route/throughroad but you have to spare a thought for the motorists trying to make progress from minor roads.

When the lights were installed at the roundabout at Dublin Airport a lot of motorists whinged about it and thought that they were pointless but prior to their installation it was virtually impossible to enter the roundabout from the R132 (northbound) as there was a constant stream of traffic from the M1.

Davidthe88 wrote:

the lights in Maynooth failed for a couple of weeks, guess what , the world didn't end , and the traffic flowed much better

Through traffic probably flowed much better to the detriment of all other routes.

Traffic lights were installed recently at a junction near my house and it has made life so much easier. I'm no longer waiting for ages for a break in the traffic to get out.

paulm17781

kearnsr wrote:

Whats your point? That the engineers cant do their jobs?

Look at the DART, Luas, M50, most other roads here, urban sprwal. I don't blame the engineers but bad design is a frequent occurrence here. Often due to political meddling but this country is full of examples of bad design.

godtabh

paulm17781 wrote:

Look at the DART, Luas, M50, most other roads here, urban sprwal. I don't blame the engineers but bad design is a frequent occurrence here. Often due to political meddling but this country is full of examples of bad design.

Thats more down to bad planning. You'll find that all engineering designs are done to standard

Zoney

kearnsr wrote:

Traffic lights on roundabout dont work

It's not as trivial as that. Roundabouts that have signals added are usually roundabouts that had become congested anyway - i.e. they weren't working due to increased traffic, change in flows or bad design. Adding the lights is probably better than leaving the junction as is.

As for installing signalised roundabouts from the beginning? That's undoubtedly cutting corners where much more needs to be spent to add some grade-separated free-flow movements. I don't know if the Magic Roundabout (Kinsale Road Roundabout) in Cork had traffic lights from the beginning, but it certainly had to have them in the absence of the missing flyover for the Southern Ring Road. Of course that flyover should have been there from the beginning, but there wasn't the cash available. So what else could be done other than have a signal-controlled roundabout?

Really, I think in a lot of cases it comes down to money rather than (or as well as) design issues. As a result there are plenty of people who hate roundabouts or hate traffic lights because they've encountered junctions treated on the cheap, where more radical (i.e. more expensive) solutions were required, such as more lanes and grade separation. Nevermind that, then you've the situations where even if the junctions were fixed, the roads leading to it are over-capacity.

paulm17781

kearnsr wrote:

Thats more down to bad planning. You'll find that all engineering designs are done to standard

I'm sure they are. A bad plan with good design is still a bad plan.

Calina

but it is then an issue with planning, not with engineering, ultimately.

godtabh

Zoney wrote:

As for installing signalised roundabouts from the beginning?

.

Sorry thats what I meant

godtabh

paulm17781 wrote:

I'm sure they are. A bad plan with good design is still a bad plan.

and still a good design

paulm17781

kearnsr wrote:

and still a good design

My God you love to have the last word. I was actually agreeing with you though it is just semantics. Now I feel obliged to find examples of bad design

perhaps

Davidth88 wrote:

Even driving down the quays , how often do you get a green , then drive 50 yds to join a queue to another red light

A well designed system would allow free flow, Blackrock is another example of bad design where lights are just irritating and seem to serve to no one's business.

godtabh

paulm17781 wrote:

My God you love to have the last word.

Some times I do!

paulm17781 wrote:

A well designed system would allow free flow, Blackrock is another example of bad design where lights are just irritating and seem to serve to no one's business

They would allow free flow but its not that easy to get the timings right when trying to manage flows on a city wide basis.

deman

I'd much rather see well-planned traffic lights than roundabouts any day of the week. Here in Finland, there are very few roundabouts and all the traffic lights are sensor-fitted so you never find yourself waiting unnecessarily. I think that the Irish powers-that-be could learn a lot at improving infrastructure by coming here and picking up a few tips.

godtabh

deman wrote:

I'd much rather see well-planned traffic lights than roundabouts any day of the week. Here in Finland, there are very few roundabouts and all the traffic lights are sensor-fitted so you never find yourself waiting unnecessarily. I think that the Irish powers-that-be could learn a lot at improving infrastructure by coming here and picking up a few tips.

It comes down to the fact that county council wont accept them because they dont under stand how they work, how they are looked after etc. They rely two much on out side help and it hurts them when it come to things like this.

invincibleirish

Zoney wrote:

I don't know if the Magic Roundabout (Kinsale Road Roundabout) in Cork had traffic lights from the beginning, but it certainly had to have them in the absence of the missing flyover for the Southern Ring Road. Of course that flyover should have been there from the beginning, but there wasn't the cash available. So what else could be done other than have a signal-controlled roundabout?

there were no lights at the roundabout from the airport/kinsale side,now they are there when they built the flyover,having to find a break in traffic with N25 traffic and N27 city traffic all going thru the roundabout was certainly a difficult experience and caused lots of delays and accidents!

Capt'n Midnight

kearnsr wrote:

Traffic lights when modelled correctly and set up correctly are an effective way of controlling traffic flows.

When incorrectly setup they are quite effective in encouraging drivers to speed. I know several sections where if you obey the speed limit you will miss the lights by a few seconds. But if you go a few kmph over the limit you'll catch them. Example being long mile road to nangor road.

Roundabouts can't handle the same volume as traffic lights and where there is a constant stream of traffic it may be hard to enter for others. Irish drivers not knowing how to indicate or which lane to be in also reduces their capacity. But they are far greener than traffic lights since there is a greater chance of negotiating them without stopping so less CO2