Assessing roundabout safety in Denmark

The precise DFS statistics and flexibility of the filter setup made it easy to conduct an analysis of the roundabout and to prove the increase in traffic safety after speed bumps were installed.

-Jonas Olesen, Head of the Project, COWI


Road safety is critical for both pedestrians and cyclists. To take the right steps towards increasing it, municipalities need to make data-driven decisions. The town of Slagelse in Denmark, striving to improve their roundabout safety, asked their partner COWI to analyze the situation. To get profound analysis, COWI utilized AI based tools by DataFromSky.

In Denmark road safety is considered to be very important in traffic planning and it is given top priority in general. There is a goal to reduce the number of fatal accidents on roads by 50% from 2019 to 2030. This sets the level of ambition for working with traffic safety in the municipalities. In Denmark bicycles are very popular so in order to achieve the goal, traffic safety needs to improve for cyclists as they are vulnerable road users.

This specific roundabout in Slagelse was a part of a traffic safety initiative across the entire municipality. There were multiple traffic accidents with cyclists, so the task was simple – make the roundabout safer based on the actual hard data.

Cowi Dánsko mapa kruháče

Utilizing video analytics

To increase safety in the roundabout, it was necessary to determine the flow and movement of all road users passing through the roundabout every day. The municipality approached the consulting group COWI to conduct the study and suggest improvements. Back then, COWI already had significant experience with drone traffic safety analytics, so they decided to apply this successful method to get accurate traffic data for all road users in the roundabout.

Thanks to fully automated DataFromSky TrafficSurvey service, COWI received accurate trajectory data for each road user based on recorded aerial videos. They uploaded the file to the fully automated online platform, applied geo-registration and requested 100% guarantee service to reach the ultimate precision in the traffic data. Geo-registration allowed to analyze distances and speeds of all objects during every millisecond of the footage and a 100% precision guarantee ensured that all traffic objects were tracked.

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Cowi Dánsko mapa kruháče


After recording the first footage with the drone, COWI was able to set up advanced filters to get the desired data outcome for their analysis. They found out that the average speed in the roundabout was 24,7 km/h. Based on that, COWI suggested the municipality of Slagelse to install speed bumps on each inbound and outbound lane to and from the roundabout. 

After the installation, COWI conducted another drone shooting to do the post-analysis and provide a full  evaluation of the effect on speed bumps. The positive change was obvious as the average speed had been lowered to
13,7 km/h
, proving a significant reduction. Details of the analysis can be found in the chart, where the data are visually presented.

COWI could simply fly the drone to do the recording and set all the analysis filters afterwards thanks to the DataFromSky TrafficSurvey. That helped them reduce the time for project preparation and gave them flexibility in adjusting the outcomes.

Slagelse by Hubertus 1

Project details

  • Use case: Traffic safety
  • Product: Traffic Survey
  • Vertical: Municipality
  • Location: Scandinavia

About Slagelse

Slagelse is a town located on the Zealand island in Denmark, being approximately 100 km from the capital Copenhagen. The town has more than 35.000 citizens and covers an area of 16,2 km2.


44,5% speed decrease

Decrease in car speed was detected thanks to the newly installed speed bumps.

Easier analysis

Thanks to advanced filtering options of TrafficSurvey, our partner COWI was able to get rich insights in no time.

Result evaluation

Our AI-powered speed measurement helped COWI to assess the impact of proposed improvements.

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As a premium partner of DataFromSky, COWI has exclusive rights for utilization of our tools in Scandinavia. For more information about this project, feel free to contact:

Line Degn Laden:

Jonas Olesen: