In the major city of Aarhus, Denmark, Road users are now reaping the fruits of Bluetooth monitoring, with shorter, more stable travel times, as well as benefiting from digital signs that help them make informed decisions.

If you drive around Aarhus with a built-in/switched on Bluetooth device, you will automatically be helping your fellow motorists to enjoy a faster and less congested journey. Aarhus Municipality, the second largest city in Denmark, has been using intelligent sensors that detect motorists’ mobile devices for several years. The data collected is used to gain an in-depth insight into and an understanding of traffic flows and the development of traffic jams, in order to optimise the road network and reduce congestion.  

Travel time savings and shorter queues
The municipality can demonstrate significant travel time savings as a result of a host of new initiatives and optimizations, using data from the small, Bluetooth-detecting sensors. A striking case in point: 

  • After the expansion of two new turning lanes and optimization of the traffic lights at the Skanderborgvej/Ringvej Syd intersection, a travel time saving of a massive 81 hours a day has been measured!. This travel time saving has been calculated solely on motorists travelling through the intersection during rush hour periods – morning and evening – and the total saving for the entire day is undoubtedly higher.
  • At the heavily trafficked Viborgvej/Runevej/Bredskiftevej intersection, the sensors have measured an average time saving, heading out of town, of as much as 31% between 3 pm and 5 pm. Travel time has also become far more stable. Where, on some days, it would take motorists around 6 minutes, the travel time is now more constant at around 2 to 2½ minutes, regardless of the time of day. This gives commuters far greater predictability.
  • With the introduction of a new left turn filter arrow from Søren Frichs Vej onto the ring road (Ringgaden), sensors have been able to detect a reduction in travel time of more than 50%.

Previously, drivers could easily sit in a queue for 10–12 minutes to turn left onto Ringgaden. With the new left turn filter arrow, it takes two to four minutes during rush hour,” explains Asbjørn Halskov-Sørensen, project manager at Center for Byens Anvendelse, CBA (the Centre for City Use).

Informative traffic signs work as intended
Last year, Aarhus Muncipality also erected 10 variable message signs on the stretches affected by light rail work, primarily Kystvejen, Randersvej and Grenåvej.
The signs, which provide information on travel times, fastest routes and other traffic information in real time, are also driven by data from the sensors. The information displayed is continually updated, in step with the actual behavior of road users. So, by considering their route and the time they set off, the motorists themselves are helping to keep the traffic moving.

A recently conducted survey shows that commuters appreciate this continuous information, which most feel makes for a more pleasant journey. Other feedback tells us that drivers become less stressed when they know in advance what to expect, traffic-wise.

The survey also shows that commuters trust the information on the signs and choose their route based on the data presented to them on their journey to and from work. Two signs out towards the E45 (state highway) reap particular praise from motorists, who find the information about the journey home especially useful.

Precise figures are crucial
“Being able to give people concrete figures – both to our politicians and to our road users – provides the basis for a far more objective and balanced debate on the things we do on the roads,” says Asbjørn Halskov-Sørensen. “It is important for us to be able to document the facts when residents and the business community address themselves to us, or further up the system, because they are experiencing long travel times/queues on various stretches. These experiences are often subjective, and travel times therefore tend to feel longer than they actually are.”

Danish Technology
The solution used by Aarhus Municipality is called BlipTrack and is produced by Danish BLIP Systems.

“The technology works by the 200 or so sensors, which are set up in and around Aarhus, detecting when a hands-free phone, mobile phone or another open Bluetooth device drives past. This allows the BlipTrack solution to calculate travel times, congestion and traffic flows,” explains Christian Bugislaus Carstens, BLIP System’s marketing manager. “The sensors do not pick up any sensitive personal information, only the device’s unique ID, which is not registered in any registers. The unique ID is also encrypted in the sensor, making it impossible to identify the Bluetooth device afterwards.”

“BlipTrack data is generally used for much more than just being able to measure the effect of signal optimisation and roadwork/construction projects, but this is clearly an important part of its application, and something from which we have benefited greatly. Ultimately, the data contributes to an improved economy and a better environment through reduced travel times and fuel consumption, and thus reductions in greenhouse gas emissions from vehicles,” says Asbjørn Halskov-Sørensen.

The future of traffic in Aarhus
“We are in the process of designing a travel time index to show how the travel time on the main approach roads and ring roads develops year by year, in the same way that we already have an index for the development in traffic volume from year to year. We expect this to be a really useful tool, enabling us to monitor and achieve the political goals set for travel times on our road network, as well as to take action at the spots where travel times have begun to increase beyond acceptable limits,” says Asbjørn Halskov-Sørensen. “In addition, we are having BlipTrack software developed to monitor the travel times of the different segments, and to raise the alarm if the travel time significantly exceeds the norm for that time and that day. We expect this to allow us to be far more on top of the situation on our roads and, for example, to be able to resolve any technical issues with traffic lights quickly.”

One solution for many purposes
Besides improving the traffic in Aarhus, BlipTrack is also implemented in more than 25 international airports including New York, Cincinnati, Toronto,Manchester, Bristol, Dublin, Amsterdam, Dubai, Genéve, Milano, Barcelona, Auckland, Brussels, Oslo, Copenhagen and Helsinki. In addition, the solution is successfully employed in optimization in road traffic in Zürich, Ireland, UK, New Zealand, USA, Canada, Denmark, Sweden and Norway. In recent years, the solution has also been implemented in ports, train stations, amusement parks, and at events all over the world.

Media Contact:


Christian Bugislaus Carstens
Marketing Manager

+45 51 16 85

BLIP Systems A/S – Haekken 2 – DK-9310 Vodskov 
+45 98 25 82 00 –