The Challenge
During the winter of 2023/24, the Danish Road Directorate used Winter Road Insights by NIRA Dynamics. One feature, Road Sensitivity, highlighted a clear pattern. Highway ramps showed poorer surface conditions compared to the surrounding highway sections. This confirmed a suspicion that ramps were more prone to low friction, but now with objective data to support it. Since ramps are locations where vehicles accelerate, slow down and change direction, understanding their winter performance quickly became a priority.
The Solution
To understand the issue in detail, NIRA Dynamics and the Directorate collaborated in conducting a dedicated analysis of the ramp conditions. For each day with winter weather, the analysis:
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Counted the low and high friction measurements on each ramp.
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Counted the same measurements on nearby highway sections.
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Calculated the percentage of low friction observations for both.
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Created a ramp to highway ratio by dividing the ramp percentage by the highway percentage.
A ratio of 2 means that ramps had twice as many low friction measurements as the adjacent highway, making friction differences easy to interpret and act upon.
The Results
With this ramp to highway ratio, new strategies for winter maintenance can be applied. Instead of using a uniform amount of salt, the Directorate can tailor treatment to the actual needs of each road type. This has the potential to improve safety and accessibility while staying within budget.
For the winter season of 2025/26, the Danish Road Directorate will continue to use Winter Road Insights to monitor conditions and guide winter operations. This ensures that every type of road receives the appropriate treatment at the right time.
