The importance of innovating with traffic lights


Traffic lights are a strange paradox on our road network. It’s hard to imagine the road without them, and at the same time it’s costing us a lot of trouble – too much trouble – to keep them in good condition. Should we just grin and bear it? No, says the author of this opinion piece, we should finally begin to innovate with those lights. When was the last time traffic control lights underwent a major overhaul? Exactly.

Article from NM Magazine, May 2016 – also available in PDF (Dutch only)

“Slipshod management of traffic lights leads to unnecessary accidents”, a headline in the daily Dutch newspaper Trouw announced recently. The occasion for the article was a study carried out by DTV Consultants, which showed that 50 percent of road managers barely takes a second look at traffic lights as soon as they have been installed. This means that even though the traffic situation somewhere may have changed drastically over the course of time, the lights continue to switch from red to green regardless. The result is that road users face unnecessary waits at a red light, and this in turn leads to unnecessary accidents, according to traffic experts quoted in the newspaper article. “If you have the feeling that you’re waiting there for nothing, this diminishes the credibility of a traffic light”, says Eric van Berkum of TU Twente. According to the experts quoted, the lack of maintenance was due to the high costs involved.

Purpose of traffic control signals

If traffic lights are indeed in such bad condition, shouldn’t we take the opportunity to have a critical discussion about them and about the way they are used? It starts with the name. Use the word ‘traffic light’ in the presence of a traffic expert, and they will probably correct you: the devices are actually called traffic control signals. In fact they are complex systems including the control computer and its housing, the poles and the lanterns with traffic lights for the red-amber-green signals, the detectors (often loops in the road surface) that feed the control computer with signals about the presence of road users, and all accompanying power supplies, cables, and leads. And before you know it, you’ve stopped talking about the purpose of traffic control signals, and are getting bogged down in technology.

As the Dutch Wegenwiki tells us, the fundamental purpose of traffic control signals is to “realize optimal handling of traffic at conflict points”. At a time in which we’re moving towards network management, the functions required of traffic control signals become even more all-inclusive. Traffic control signals are also being deployed very deliberately to buffer traffic to ensure that queues downstream don’t become so long that vehicles have to stop on intersections, thus blocking traffic crossing the intersection in other directions (‘blocking back’). Or, as was the case in the PraktijkProef Amsterdam West, to support ramp metering to prevent congestion on the motorway.

Conversely, traffic control signals can also be used to ramp meter the inflow into a city from a motorway. In short, traffic control signals are a powerful control instrument in network management, and this requires that we focus on functionality – not on the technology used. Ultimately, what traffic lights do is to instruct road users to stop and wait for the sake of a higher network goal.


So what has gone wrong if, as this study shows, the functional condition of many traffic control signals is not in order? Traffic control signals developed in the past into control instruments that perform their task in isolation: realizing optimal handling of traffic at conflict points. In some cases, they are linked through coupling cables, so that green waves can be created along the road section covered by the coupling cable. Practically everything is laid down in the technology as it has been deployed along the roadside.

Later the first traffic signal control rooms were set up, to monitor the technical condition of the traffic control signals. These made it possible to make functional adjustments by reconfiguring traffic control schemes so as to make them better attuned to new traffic situations. Many road managers now have their own traffic control room, in which a traffic signal control room occupies an important position in addition to a network management system (NMS). The NMS can be used to activate control scenarios whenever the traffic situation changes, which leads – through the traffic signal control room – to the reconfiguration of current control schemes, or the deliberate choice to deploy a different control scheme that is more suited to the traffic situation at the time. This is the path we should be going down, and it is an opportunity for further growth, as the PraktijkProef Amsterdam and the Control Approach derived from it have shown. This means that the functional condition of traffic signals isn’t checked and adjusted every few years, but continually throughout the day and the week.

Cost is, once again, the limiting factor. In order to realize this, traffic control signals must first be taken out of their isolation; they have to start communicating across long distances with the traffic signal control room. This can be done using copper wire or fiberglass, but there are now also wireless communication technologies, or a combination of both. England already has excellent examples of traffic control signals that are part of a mesh network through wireless communication technology, with only one traffic control signal linked to fiberglass to control communication between the mesh network and the control room. In addition, traffic control signals have to be equipped with a whole series of traffic control schemes to be able to meet a varied set of possible traffic situations. Ideally, communication between the control room and the traffic control signals takes place using the open IVERA protocol, with data from the traffic control signals extracted in open VLOG format, which gives the traffic control room an indication of the number of passing road users. Older traffic control signals will have to be adjusted technically to make this possible.

System set-up

Adding this kind of technology to traffic control signals’ existing system set-up, significantly increases their added value (certainly at network level), but it doesn’t really bring the costs down. To do that, we have to look at the system set-up itself. What was the last year that real innovation of traffic control signals took place? Why can’t traffic control signals functionally maintain themselves? In an age in which we’re working on autonomous vehicles, it’s difficult to retain the existing approach where traffic control schemes are made manually, compiled, and then loaded onto the traffic control signal on the control computer. Every step in this process costs time and money, and as the study has shown, it results in traffic control schemes that are out of date and do not grow along with the changing traffic situation. In other words: we want traffic control signals that are autonomous in functional maintenance.

We also want traffic control signals whose system set-up is geared to the great developments of our time, such as cloud computing, mesh networking, and the internet of things. Developments that have brought innovation and reduced cost in many fields, but are only trickling down into the world of traffic. And we want traffic control signals that don’t just look like traffic lights to the road users, but that also explain why road users have to stop and wait. Socially communicative traffic control signals, that make it easier to use them to buffer the traffic to prevent congestion downstream.

Innovate first…

If we are aware that traffic control signals have a particularly useful function in safely and more efficiently using the available road infrastructure, and if we also know that the cost of maintaining this function is too high, then it is our responsibility to engage in open innovation instead of cutting off the debate immediately by pointing at rules from the past and at road safety. Innovate first; the rules can be adjusted afterwards. Road safety of course is a primary concern, but it’s precisely the current situation that is lacking in this respect.


  • Paul van Koningsbruggen
  • Director Mobility
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