Car accidents caused by unintentional run off road (in this paper the term “inadvertent lane departure” is used) have become an important topic within world wide accident research activities. These accidents can be addressed by lateral support systems (e.g. Lane Departure Warning) which are considered by experts to be the second most important active safety countermeasures after forward collision intervention systems.
There is no common understanding for “run off road” yet. This term is being used both for the event of a departure from the own driving lane and for the event of a departure from the road. But it is known that when a driver leaves its driving lane unintentionally, it mostly results in a severe crash involving an oncoming vehicle or an obstacle (e.g. tree).
The importance of this topic is also visible as efforts have already been made in order to adopt this issue in current and future testing procedures (eg. NHTSA, IIHS, Euro NCAP).
In Germany, the relevance of unintentional run off road accidents can hardly be estimated when using only official numbers. Official statistics categorize accidents by the parameter “leaving the carriageway” without any differentiation between intentional or unintentional lane departure. However, in the year 2013, these accidents made up 14% of all accidents with personal injury involving all kinds of road users but 30% of all fatalities and 23% seriously injured persons. A more accurate view on the accidents that match the definition “unintentional run off road” was given by UDV in an earlier study (paper-09-0317).
This paper presents now the results of a second more detailed analysis which was carried out with up-to-date accident data. For the analysis, the In-depth database of the German Insurers (UDB) was used. It contains a representative cross section of all third party insurance claims reported between 2002 and 2011. The group of car accidents analyzed was defined as “unintentional run off road accidents” and implies only cases where a car had left his driving lane unintentionally. The aim of the analysis was to get a better understanding of the circumstances at which these incidents occur and to derive key accident scenarios.
From a total of 118 relevant cases in the database, which account for 5% of all accidents caused by a car, five accident scenarios were deduced. These make up 68% of the accidents and 66% of the fatalities in the datapool. Some of the main results were: A lane departure to the left occurred more frequently than a lane departure to the right. Generally, the lane departure was followed by a collision with an oncoming vehicle (in 70% passenger car) rather than by a run off from the road. Regarding behavioral issues, health problems of the driver were found to be twice as frequent as distractions of any kind.