In Aarhus, Cyclists Control Traffic Lights For a Smoother Ride

By Claire Swedberg

The Danish city is testing a system provided by RFID company ID-advice that turns the light green when it detects the presence of a bicycle at the intersection.


Editor’s note: This story first appeared in on December 15, 2015

Traffic lights are going green for cyclists automatically at one particular intersection in Aarhus, Denmark, with the city’s pilot deployment of a passive radio frequency identification solution, known as 2Green, provided by ID-advice. With RFID tags attached to bicycles and readers installed at the intersection, the system can detect when a cyclist is approaching, and forward a prompt to the traffic-signaling software to switch the light facing the bike to green, while turning the cross-traffic light to red. That data is also collected for analytics purposes.

The solution is part of the European project known as Radical, launched in 2013 to develop smart cities using Internet of Things services. Six cities from as many European countries are taking part in the Radical project, using a variety of technologies for other smart-city applications. “Since Aarhus is known to be—and also has a clear strategy to be—a cycling city, and also has a clear strategy to be a smart city, it was a perfect match” to combine the RFID technology with bicycle safety, says Aarhus city-development consultant Louise Overgaard.

At one of Aarhus’ busy roads, the city installed two RFID readers, one at each side of the intersection, to identify the presence of bicyclists.

Aarhus, the second largest city in Denmark, is home to thousands of cyclists, many of whom are university students. The city opted to test a system that would enable a select number of cyclists to safely move through intersections quickly, while compelling vehicles to always stop when those bicycles are in the intersection. The solution, however, needed to be flexible enough to be bypassed in some cases, such as the presence of an emergency vehicle.

The city has already been working on a project focused on improving bicycle access to the city center for commuters living in the suburbs, according to Pablo Celis, the manager of Aarhus Cykelby (Aarhus Cycle City), an agency that is part of Aarhus’ road division and is heading the RFID project. In that effort, the city has installed a bicycle “superhighway” consisting of a bike lane that cyclists can use to travel 15 to 20 kilometers (9.3 to 12.4 miles) from outside the city to the commercial district. (Additional bike superhighways are in the works.)

The superhighway enables cyclists to quickly get to the city, but once they arrive, traffic lights can cause delays and frustration. Therefore, Aarhus opted to test a solution from ID-advice, a Danish RFID firm established in 2012. According to Rita Westergaard, ID-advice’s business solutions manager, her company offers low-frequency (LF) and high-frequency (HF) RFID technology for tracking laundry and tools, and for use in science centers, as well as ultrahigh-frequency (UHF) technology for sports and cultural events. The company is now marketing a commercial version of the 2Green light-changing technology.

The city decided “to test the service in a carefully selected junction,” Overgaard says. It sought an intersection with a high level of bike traffic and fewer motorized vehicles, she explains, “and also a spot where the cars don’t drive that fast.” At the selected intersection, ID-advice installed two Scirocco R610 RFID readers wired to Scirocco A100 reader antennas to capture each UHF tag’s ID number.

ID-advice opted to use passive Confidex Carrier UHF RFID tags, Westergaard says, because they performed best in this application, based on their reading distance—4 to 8 meters (13.1 to 26.2 feet)—and the ease with which they could be mounted on a bicycle. In addition, she notes, they were well suited due to their light weight. “We tested many tags,” Westergaard states, “but this was the best compromise for the prototype.”

Louise Overgaard, an Aarhus city-development consultant

The city then distributed 200 of the tags to cyclists in the area. A tag was fastened to each bike’s front wheel via a cable tie. Two readers—one on each side of an intersection—were installed at a spot where the bike lane crossed a vehicular road, so that a bicycle tag’s ID would be captured regardless of whether it was moving.

When a bicycle comes within range, the reader captures its tag’s unique Electronic Product Code (EPC) ID number—which, for privacy reasons, is not linked to any information regarding the bike’s owner. That software on the reader verifies that the ID is that of a bike tag and forwards instructions to the traffic light’s built-in software, via an output signal, to change the light to green in the cyclist’s direction. The traffic-light control software has been programmed so that, in some instances, the 2Green technology is overridden in order to ensure that vehicles pass safely through the intersection.

The reader also forwards data, via a cellular connection, to the Radical software platform—a data repository designed for use in replicating smart-city services in other cities—on the Radical program’s server. The collected information is also sent to an open-source CKAN platform, where the public and city managers can access traffic data. ID-advice software integrates with the Radical and CKAN platforms, thereby providing data regarding how, when and how many bikes passed through that intersection. The city’s website, available to the public, displays the number of bicycles that move through the intersection on a daily or weekly basis.

The system has been popular with cyclists, according to Overgaard. “It is very easy to sell green lights to cyclists,” she states. “They find it to be a good idea. They are, of course, interested in safe and convenient travels through the city.”

At this point, the system is still only being used in a limited pilot. “If we evaluate it positively, we plan to install 1,000 bicycle tags and expand it to other junctions,” Overgaard says.

So far, 200 of the city’s residents have been issued an RFID tag, which is fastened to a bike’s front wheel via a cable tie.

The Radical project is slated to end in February 2016. However, Westergaard says, ID-advice expects the installations to remain in operation and the city to install additional readers within the city center during the years to come.

ID-advice’s Rita Westergaard

“The future for this exact service is not clear yet,” Overgaard says, “but we will continue to work on regulating the traffic in a smart way.”

The next generation of ID-advice’s 2Green solution will feature a new tag designed to be easily snapped onto a bike. This tag will contain a Smartrac DogBone inlay made with an Impinj Monza 4D chip. “We have tested the Monza 4D DogBone and saw a very good performance,” Westergaard says. The next-generation system will also include solar panels to power the readers.