Variation of traffic flow due to accumulated snow formation on road

Abstract

Sapporo City has one of the heaviest snowfalls worldwide, and the road conditions in winter are getting remarkably worse. Snow removal works in winter are indispensable in order to secure traffic functions in the city. Snow accumulates on roads as soon as it is removed. It is also a problem that the deposited snow protrudes into the lanes of roads and the traffic flow drops. This study analyzed the size of deposited snow formation and the variation of traffic flow. We set up a camera for a four-lane road managed by Sapporo City (two lanes per side) and observed two seasons continuously. Width of deposited snow and traffic performance (Traffic Volume - Velocity) were analyzed based on the acquired images. The width of deposited snow was from 1.0 m to 2.5 m. When the width of the deposited snow exceeded approx.1.5 m, it was indicated that only one lane of the road will be in operation if it is originally operated as two lanes per side, with about 70% of the traffic volume and about 80% of the speed. In addition, based on the actual situation of use of bicycles and pedestrians in autumn, we propose redistribution of road cross-sections considering snow coverage width.