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

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. Copyright © 2011 Royal Meteorological Society

[1]  Snow Crystal Forms and Riming Effects as Related to Snowfall Density and General Storm Conditions , 1964 .

[2]  Mircea-Paul Andreescu,et al.  Weather and traffic accidents in Montreal, Canada , 1998 .

[3]  Jean-Marie Carrière,et al.  A climatological study of surface freezing precipitation in Europe , 2000 .

[4]  M. Eriksson,et al.  Relationships between road slipperiness, traffic accident risk and winter road maintenance activity , 2000 .

[5]  B. Bernstein.  Regional and Local Influences on Freezing Drizzle, Freezing Rain,and Ice Pellet Events , 2000 .

[6]  Nolan J. Doesken,et al.  Density of Freshly Fallen Snow in the Central Rocky Mountains , 2000 .

[7]  Jerry M. Straka,et al.  Bulk Hydrometeor Classification and Quantification Using Polarimetric Radar Data: Synthesis of Relations , 2000 .

[8]  Sergey Y. Matrosov,et al.  On the Use of Radar Depolarization Ratios for Estimating Shapes of Ice Hydrometeors in Winter Clouds , 2001 .

[9]  M. Karlsson.  Prediction of hoar‐frost by use of a Road Weather information System , 2001 .

[10]  Hanna-Leena Merenti-Välimäki,et al.  Present weather: comparing human observations and one type of automated sensor , 2001 .

[11]  R. Hogan,et al.  Properties of embedded convection in warm‐frontal mixed‐phase cloud from aircraft and polarimetric radar , 2002 .

[12]  Ari Venäläinen,et al.  The FMI Road Weather Model , 2006 .

[13]  G. Cox,et al.  Aircraft and dual polarization radar observations of hydrometeors in light stratiform precipitation , 2007 .

[14]  G. Thompson,et al.  Observations of Freezing Drizzle in Extratropical Cyclonic Storms during IMPROVE-2 , 2007 .

[15]  Markus Pöllänen,et al.  Wintertime road conditions and accident risks in passenger car traffic , 2008 .

[16]  D. Moisseev.  Dual-polarization weather radar observations of supercooled water and enhanced ice multiplication areas , 2009 .

[17]  I. Juga,et al.  Snowfall induced severe pile-ups in southern Finland on 17 March 2005 , 2009 .

[18]  Timo Sukuvaara,et al.  Wireless traffic service platform for combined vehicle-to-vehicle and vehicle-to-infrastructure communications , 2009, IEEE Wireless Communications.

[19]  Harri Hohti,et al.  Quality assurance in the FMI Doppler Weather Radar Network , 2010 .

[20]  R. Doviak,et al.  POLARIMETRIC DOPPLER WEATHER RADAR , 2022 .