Traffic Lights vs Roundabouts at busy urban junctions

AugustusMinimus wrote: »

No, traffic lights on a roundabout indicates that a roundabout is not a suitable junction for the location.

Once you are forced to put lights on a junction, the junction should be replaced by a fully free flow junction.

This is true, but "should be" doesn't cut any mustard in terms of road expenditure in Ireland.

In an Ideal world (which our road network most definitely is NOT) once a junction is over capacity, an automated predictive analytics traffic management solution would manage the traffic signals over a wide area (not just the junction in question, but many junctions around it and leading up to it) in real time, changing light timings on the fly in an integrated fashion, and ensuring that any traffic buildup is mitigated or diverted as much as possible and the build up is dissipated.

This is the state of the art of traffic management technology and predictive analytics at the moment, it's different to systems which rely on historical data and patterns, and is more like a live brain, reacting to situations as they happen and predicting what it might mean for traffic in a certain sector in say 5 or 10 minutes time. I know because i work for one of the world leaders in the back end technology for those kinds of systems (not saying which one) and have seen infrastructure and solutions in this area in action, and they are amazing to watch. Think of the M50 toll cameras, but on every major road, all over the city, keeping an eye on traffic flows, speeds, and vehicle counts, and managing ALL local traffic light timings automatically to ensure everywhere is kept flowing as freely as possible, and you'll get the idea.

Aside from that kind of system (which would be waay out of our budget) the next best option would be full scale free-flow junctions replacing the existing lighted junctions or roundabouts where problems of capacity occur, but as we know, despite having an extremely high level of motor and roads taxation in Ireland, very little of it is ringfenced for infrastructural investment in the roads network, and even if we had the cash, major refits like this would be an engineering nightmare because of lack of proper foresight, planning, and provision for expansion which has been rife in Ireland for half a century or more.

Case in point. Look at the Newland's Cross junction in Dublin, a mile or so from the Red Cow interchange on the M50. A standard crossroads type traffic light junction, managed by static pattern traffic lights, a mile from the busiest interchange on the busiest motorway in the busiest city in the country. All the major surrounding road infrastructure has been retrofitted in recent years and has seen massive traffic spikes over the last decade or two, but this junction, an integral part of that area's system, has remained relatively unchanged. It was not built to withstand anything close to the volume of traffic it now holds, and as anyone who uses it regularly will tell you, it is backed up in all directions most of the time, but is particularly severe during peak hours, as it is fed from all sides by heavy private & commercial traffic from motorways office parks, and various industrial and residential areas.

Look at the problem it poses from a traffic management infrastructure point of view. its surrounded on all sides by thriving businesses and premises, so there is no further physical space to expand it's capacity, a roundabout in it's place would cause complete pandemonium and probably wide scale murder, road rage, and gridlock on a daily basis, and due to the lack of integrated spatial planning, a freeflow junction at the location would necessitate multiple compulsory purchase orders and the leveling of many thriving commercial properties, hotels, restaurants, and residences around it to make space for the build. Tunneling to create underpasses would run into the same issues and would be prohibitively expensive in the current economic situation. So what's the solution? The only way to fix newlands cross is to rip it up and start again from scratch, which would itself cause traffic pandemonium while it was happening.

My point, after all that, is that we have to start looking at these problems from an integrated perspective. It's not good enough to fix a single junction or a crossroads or a roundabout, as we have always done. We have to look at the whole system, because every time we don't plan properly, a retrofit later on when we can't ignore the problem anymore costs ten times as much and works half as well as it should.