Analysis of weather factors responsible for the traffic ‘Black Day’ in Helsinki, Finland, on 17 March 2005

Abstract

During the morning rush hours of 17 March 2005, a band of intense snowfall affected the Helsinki metropolitan area in southern Finland. The event caused severe pile-ups on the highways, with almost 300 crashed cars, the deaths of three people and more than 60 people injured. The snowfall was soon followed by freezing drizzle. Some of the media later blamed this as being responsible for the unprecedented number and severity of the accidents that had occurred. However, the official inquiry came to the conclusion that the pile-ups had been caused by the very poor visibility due to intense snowfall and excessive driving speeds combined with reduced road surface friction. In this study, these two viewpoints are investigated, by using high time-resolution dual-polarization radar observations to analyse the changes in intensity and form of the precipitation leading to the event. The radar data were particularly useful in supplementing weather observations.

Weather Conditions, Weather Information and Car Crashes

“…An important distinction between approaches is formed by the prime orientation of the analysis, i.e. the driver, the vehicle, a combination of driver and vehicle, the infrastructure (and its immediate environment), (weather) events, accident hotspots, and injury vs. accident [6][7][8][9]. Furthermore, studies assessing the effectiveness of road transport safety policies need to be cross-cutting in order to avoid risks of erroneous attribution of effects to trends or measures [10][11][12].…”

“…In car crash research, microscopic studies are concerned with assessing the mechanisms directly leading to a particular accident or a particular type of accident. In research focusing on crashes caused by weather conditions, this approach is typically based on case studies of bad weather events [7]. Macroscopic studies deal with system level developments, and have-at least in principle-the ambition of taking into account all types of road safety factors and the road safety policy programmes as well.…”

Observation of a freezing drizzle episode: A case study

“…This precipitation can negatively affect homes, infrastructure and wind power generation, and cause power outages (Norrman et al, 2000;Juga et al, 2012).…”

Snow cover trends in Finland over 1961–2014 based on gridded snow depth observations

“…Northern European countries such as Finland are highly sensitive to variability and changes in snowfall and snow cover. Intense snowfall may cause severe problems for traffic and electricity supply (Andreescu and Frost, ; Andersson, ; Juga et al, ; Vajda et al, ; Lehtonen, ), and maintaining sufficient snow removal equipment requires financial resources (Keskinen, ; Lehtonen, ). Snow cover conditions and the changes in them also impact reindeer herding (Hansen et al, , ; Rasmus et al, , ; Turunen et al, ) and boreal agriculture and vegetation, especially in spring (Bjerke et al, ; Peltonen‐Sainio et al, ).…”