4.2. Accident data and method of analysis
The data on winter navigation accidents available for this study cover four winters: 2002–2003 (ice-related accidents reported to the Finnish Maritime Administration during winter 2002–2003), 2009–2010, 2010–2011, and 2011–2012 (accidents reported on Finnish waters by the Finnish Transport Safety Agency during the winter ice periods from 2009 to 2012). Of these winters, two are regarded as average winters (2009–2010 and 2011–2012), the first covering a sea ice period from 25 of December 2009 to 25 of May 2010 and the second period from 14 of January 2012 to 3 of May 2012. Two of the winters are regarded as severe (2002–2003 and 2010–2011), the first covering a sea ice period from 7 of November 2002 to 19 of May 2003 and the second from 29 of November 2010 to 22 of May 2011.
The accident data only covered accidents reported to the Finnish Maritime Administration (FMA) and Finnish Transport Safety Agency (FTSA) in Finnish maritime areas during the time periods mentioned. The original information provided by FMA and FTSA contains the following data: the date of the accident, type of accident, type of vessel involved in the accident, vessel characteristics (length, beam, draft and deadweight) and/or vessel name, and the coordinates of the accident. In the data from 2009 to 2012, a qualitative description of the severity of the accident is also included.
The accident data have been analysed from three perspectives. First, a high-level descriptive analysis is performed for gathering background knowledge about the accident types, types and main characteristics of the vessels involved in the accidents, areas of accident occurrence, and ice conditions during the accidents. Second, a more detailed descriptive analysis focuses on the winter navigation operations, creating knowledge about the specific ice conditions and ship characteristics of the accidents in different operational modes. Third, comparisons between the hazardous scenarios identified by the experts and the scenarios detected in accident statistics are performed, particularly for the analysis of ice conditions. This information is subsequently applied to construct a set of risk matrices.