Unique Model Calculates Costs of Winter Maintenance

Winter road in snowstorm

Photo: Thinkstock

In the late 1990s, VTI and the Swedish Transport Administration (then known as the Swedish Road Administration) began discussing the creation of a model for calculating the socioeconomic costs of various strategies for the winter maintenance of the national road system. VTI has now been working for nearly 15 years to develop and refine the Winter Model. In summer 2014, the researchers had made sufficient progress to be able to report the results of a first complete working version of the model to the Swedish Transport Administration, which commissioned the project.

The Winter Model can be used to answer questions such as: How does the number of accidents change if the winter maintenance strategy is changed? What happens in terms of energy consumption if the standard class to which the road has been assigned is changed? How does the cost of winter maintenance affect the average speed on the road?

The model can be used, for example, to calculate what the cost to society would be were the operating standard along parts of the road system to be lowered by discontinuing salting and switching over to just ploughing and sanding. The model takes into account factors such as the costs of maintenance, accidents, fuel consumption, and environmental impact.

“In this sense the Winter Model is a unique tool, as it not only calculates the costs of maintenance activities but also takes into account the costs to those who use the road and to society as a whole. And it is really brilliant that we have now progressed to the point where we have got it to work to calculate data for an entire winter”, says VTI researcher Anna Arvidsson.

Many shared in the work
Arvidsson has been working at VTI for nearly five years and was not present when the Winter Model first began to take shape. Over the years, many at VTI have shared in the work. The Winter Model is primarily associated with now-retired VTI employees Staffan Möller, Gudrun Öberg, and Carl-Gustaf Wallman.

“The Winter Model, and my former colleagues who worked so hard on it, are in fact quite well known out in the world among the small group of people engaged in research and development pertaining to winter maintenance”, says Arvidsson.

She hopes to give a presentation on the Winter Model at the international PIARC Winter Road Congress in South Korea in November 2015.

Unique Swedish model
During her years working on the model, Anna has been able to confirm that there is no other model in the world quite like the one developed by VTI. On the other hand, many countries have developed their own decision-support systems used in making decisions as to what winter roadwork should be carried out or to provide information to highway authorities and road users.

Work on the first full set of calculation results from the Winter Model was completed in summer 2014. In VTI Report 826, which was published at that time, researchers made seven comparisons between different application runs. This was done to study the changes in socioeconomic costs when the standard class to which the road had been assigned was changed. The standard class defines how much snow must fall before action is taken and/or how much time can pass before a road’s condition is ameliorated.

Costs rise if standard classes are lowered
The results of all comparisons indicate that when the standard class is lowered, the total socioeconomic costs increase. The accident-related costs consistently account for the highest cost increases in all comparisons. One reason is that when the standard requirements are lowered, or a salted road becomes an unsalted road, the duration and extent of road conditions involving snow and/or ice, under which there is greater accident risk, increase. Travel-time costs also account for a large share of the total costs, and these costs increase as a result of the degraded road condition in all comparisons.

About the Winter Model

  • Developed by VTI in cooperation with the Swedish Transport Administration
  • A strategic Winter Service Management System (WSMS)
  • Calculates and evaluates socioeconomic costs associated with various winter maintenance strategies and activities, taking into account costs to road users and to society as a whole
  • Consists of six interacting models; the hub is the Road Condition Model, which controls calculations in the following:
    • the Accessibility Model, which indicates how vehicle speeds and traffic flows vary with road conditions
    • the Accident Model, in which accident ratios, accident types, and consequences associated with various road conditions and their durations are calculated
    • the Vehicle Cost Model, which covers fuel consumption and corrosion due to road salt use
    • the Environment Model, which describes the impact primarily of salting on exposed roadside vegetation
    • the Road Maintenance Costs Model, which calculates the direct costs of winter road maintenance activities

Text: Katarina Nestor

VTI report 826: The Winter Model – Calibration and Further Development of the Winter Model.
Author: Anna Arvidsson.
Link to report (in Swedish with English summary)

Image of Anna Arvidsson Contact:
Anna Arvidsson
VTI, Sweden
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