  This paper defines a methodology with in-depth data to identify the skills
needed by riders in the highest risk crash configurations to reduce casualty
rates. We present a case study using in-depth data of 803 powered-two-wheeler
crashes. Seven high-risk crash configuration based on the pre-crash
trajectories of the road-users involved were considered to investigate the
human errors as crash contributors. Primary crash contributing factor, evasive
manoeuvres performed, horizontal roadway alignment and speed-related factors
were identified, along with the most frequent configurations and those with the
greatest risk of severe injury. Straight Crossing Path/Lateral Direction was
the most frequent crash configuration and Turn Across Path/ Opposing Direction
that with the greatest risk of serious injury were identified. Multi-vehicle
crashes cannot be considered as a homogenous category of crashes to which the
same human failure is attributed, as different interactions between
motorcyclists and other road users are associated with both different types of
human error and different rider reactions. Human error in multiple-vehicle
crashes related to crossing paths configurations were different from errors
related to rear-end or head-on crashes. Multi-vehicle head-on crashes and
single-vehicle collisions frequently occur along curves. The involved collision
avoidance manoeuvres of the riders differed significantly among the highest
risk crash configurations. The most relevant lack of skills are identified and
linked to their most representative context. In most cases a combination of
different skills was required simultaneously to avoid the crash. The findings
underline the need to group accident cases, beyond the usual single-vehicle
versus multi-vehicle collision approach. Our methodology can also be applied to
support preventive actions based on riders training and eventually ADAS design.
