Causation patterns and data collection blind spots for fatal intersection accidents in Norway

Norwegian fatal intersection accidents from the years 2005-2007 were analysed to identify any causation patternsamong their underlying contributing factors, and also to evaluate whether the data collection and documentation proceduresused by the Norwegian in-depth investigation teams produces the information necessary to perform causation patternanalysis. A total of 28 fatal accidents were analysed. Details on crash contributing factors for each driver in each crash werefirst coded using the Driving Reliability and Error Analysis Method (DREAM), and then aggregated based on whether thedriver was going straight or turning. Analysis results indicate that turning drivers to a large extent are faced with perceptiondifficulties and unexpected behaviour from the primary conflict vehicle, while at the same time trying to negotiate ademanding traffic situation. Drivers going straight on the other hand have less perception difficulties. Instead, their mainproblem is that they largely expect turning drivers to yield. When this assumption is violated, they are either slow to react ordo not react at all. Contributing factors often pointed to in literature, e.g. high speed, drugs and/or alcohol and inadequatedriver training, played a role in 12 of 28 accidents. While this confirms their prevalence, it also indicates that most driversend up in these situations due to combinations of less auspicious contributing factors.In terms of data collection and documentation, information on blunt end factors (those more distant in time/space, yetimportant for the development of events) was more limited than information on sharp end factors (those close in time/spaceto the crash). A possible explanation is that analysts may view some blunt end factors as event circumstances rather thancontributing factors in themselves, and therefore do not report them. There was also an asymmetry in terms of reportedobstructions to view due to signposts and vegetation. While frequently reported as contributing for turning drivers, they wererarely reported as contributing for their counterparts in the same accidents. This probably reflects an involuntary focus of theanalyst on identifying contributing factors for the driver legally held liable, while less attention is paid to the driver judgednot at fault. Since who to blame often is irrelevant from a countermeasure development point of view, this underlyinginvestigator mindset needs addressing to avoid future bias in crash investigation reports