Stockholm has a stated goal that the proportion of all journeys made by bicycle will increase, even during the wintertime. For cyclists' safety, it is especially important to ensure an adequate friction. In Sweden one of the main reasons of cyclist's accidents is slipping, primarily due to ice and snow but also because of remaining gravels originating from winter gritting. One method that could contribute to a higher standard of bike paths in winter is "sopsaltmetoden" applied today in some Swedish municipalities. The method involves a sweeper cleaning the snow and fighting with saline or moistened salt. In the context of a PhD project at VTI and KTH made several studies on the use of the method in Linköping, but since then no detailed monitoring or evaluation made in Sweden.
moistened with saline or salt. In the context of a PhD project at VTI and KTH made a
The aim of the project was to investigate possible improvements to the methodology, equipment and strategy to achieve a more optimal use under coming winters, where the salt content is kept as low as possible without compromising safety.
In the winter of 2012/13 tested the city of Stockholm a few pieces of equipment for sopsaltning on selected cycling routes in Stockholm. Since the winter of 2013/14, there is a wider application of the method of some selected major cycle routes for commuters. On behalf of the City of Stockholm, VTI has made evaluative measurements at six selected sites along these routes. There were observed the road conditions what was supplemented with measurements of friction and salt quantities. In addition, measures have been followed up by incident reports and driver record review and interviews with managers and drivers.
Peab, which has been responsible contractor, during the winter of 2013/14 had access to five vehicles for sopsaltningen, in different combinations: Lundbergare roller brush with forward and Falköping DISCSPREADER on a semi-trailer; Wille with sweeper back and Schmidt plate spreader on a semi-trailer; and Multihog with combined plow and sweeper back and a spraying boom with nozzles for salt spreading the rear of the vehicle. Multihogen can only spread brine, but may be varied from 5 to 25 grams per square meter. Falköpings and Schmidt spreaders are both of type "DISCSPREADER" which means that it is possible to add both saline moistened or dry salt. Then the amount of salt is varied from 0 to 40 grams per square meter.
The goal for the winter 2013/14 was to maintain a very high standard on the selected cycle routes. Throughout the winter season, drivers will drive their distances almost every day, whether it needed some winter action or not. In early winter, the sweeping would help to bike lanes free of dirt, twigs, fallen leaves, etc. At the risk of slipping, it would also be salted, as long as the temperature was above -12 ° C. Some restrictions to keep down the amount of salt was in principle not used this winter. At lower temperatures and / or a lot of snow would be ploughed and sanded instead and then return to sopsaltning as soon as it became mild again.
Winter 2013/2014 was overall very mild in Stockholm as well as in the rest of the country. It snowed only on a few occasions and in most cases only moderate amounts of snow. This meant that there was no need to go over to the ploughing and sanding without using of sopsaltning method. According intervention reports were the first
action in Västerort November 14 and in southern Stockholm on 2 December. Subsequently, pedestrian and bike paths swept and slip fought almost every day up to and including 27 March, in both areas. The first snowfall that required a snow removal effort occurred on 11 January. Then were required snow removal for another six days in January, three days in February and three days in March.
Road conditions observations clearly show that sopsaltningen resulted in better conditions than traditional ploughing and sanding. It has basically always been snow-free conditions in the sopsaltade streets, even when there has been snow and ice on the cycling route that are not salted.
VTI's measurements also show that the friction was in average significantly higher on the sopsaltaded streets compared with the strings that are not salted. VTI
friction measurements show that the friction can vary quite a bit along the sopsaltade
For the safety of cyclists, it is important to provide information on where slipping could occur. For the road it is also important to know these parties for more targeted deicing operations but also that through the design and construction measures reduce the risk of slip occurring.