100 yeas old: Traffic lights switch to smart mode

July 25, 2014 // By Christoph Hammerschmidt
These days, the electric traffic light is going to celebrate its 100th anniversary: On August 06, 1914, the municipal authorities in Cleveland (USA) put the first traffic light into operation. Though today's traffic lights are operating on much the same principle, the successor already appears at the horizon: The smart intersection in which the vehicles and the infrastructure mutually ensure smooth traffic flow.

There was a long way to go from the first traffic light to today's automatic traffic management systems at complex intersections. In the early years, the traffic lights were switched manually. Later, simple relay switches controlled the traffic in a rather schematic way. Today, traffic lights are controlled by multiple sensors such as induction loops, embedded in the tarmac, or infrared sensors and / or proximity sensors. Embedded computers that process the sensor signals and thus offer a certain degree of intelligence and adaptivity have displaced the dumb arrays of relays that commanded the traffic flow.

Now it is again time for a change: More intelligence, more information will regulate the priorities in future intersection. This topic is part of UR:BAN, a joint research project in Germany that aims at better traffic management and collaborative driver assistance systems. Ralf Kutzner from the Institute for traffic engineering and infrastructure planning of the Braunschweig Technical University describes what a smart intersection is about. "Much like the designers of the first traffic light systems, we are guided by the idea to make traffic more safe, efficient and - this is the new component - low in emission."

Towards this end, the researchers utilise tools like traffic flow simulation and modelling. And they will have an instrument at their disposal earlier generations did not have: Connectivity. The research team wants the vehicles to "talk" to each other and to the traffic light control system. The data generated by this car-to-infrastructure (C2X) system are fed into the traffic flow management system which uses these data to generate an image of the traffic parameters (density, speed, direction etc). Based on these data, the traffic flow can be optimised on the fly. But keeping the traffic going is not only the business of traffic lights.

Connected driver assistance systems can also utilise these data and compute the optimum speed for each single driver. This helps the driver