Measuring travel time in the Limfjord Tunnel on E45 – The first trail ever

The Limfjord Tunnel is an important part of the infrastructure in Northern Jutland. Accurate travel times in the tunnel are valuable tools in traffic analysis. 

Hosting the only highway that reaches the northern part of the Danish mainland, this piece of E45 is, without a doubt, the most heavily trafficked route in the region. The high number of vehicles passing the Limfjord each day, made the tunnel a challenging testing ground for a BlipTrack™ solution. We needed to find out, if we were able to measure the journey time between two points at a Danish Highway. The challenges did, however, raise some further questions:

• We knew the numbers of vehicle passing the tunnel how many vehicles would we actually measure?
• Would we be able to calculate an approximate Bluetooth penetration?
• How many Bluetooth radios would we detect per vehicle?
• How many sensors would we need to cover all four lanes?
• Would we be able to pick up the Bluetooth signal from fast moving vehicles?

Simple solution – great result

We placed two battery driven BlipTrack™ sensors north and east of the Limfjord Tunnel. They were located approximately 15 meters from the roadside. These sensors were connected to the backend BlipTrack™ servers via 3G modems. This setup was not in anyway rocket science – but it provided us with a wealth of information.

During the trail period of 61 days more than 14.000 detections of vehicles was made every day. More than 140.000 unique Bluetooth IDs were seen in the whole period. Travel time calculations were based on more than 5000 complete measurements every day. The measured Bluetooth penetration was 29,2% and the corrected penetration figure is 20,8%. There were 1.4 Bluetooth units per vehicle.

The conclusion is clear. A BlipTrack™ solution is up to the task of measuring travel times on Highways. 

• The Bluetooth sensors can pick up signals from vehicles driving up to 200km/h.
• The measured Bluetooth penetration was 29,2% and the corrected penetration figure is 20,8%. There were 1.4 Bluetooth units per vehicle.
• One sensor easily covers a highway with two lanes in each direction.