6Powered two wheeler (PTW) riders are a group of vulnerable road users that are 7 overrepresented compared to other road user groups with regards to crash injury 8 outcomes. The understanding of the dynamics that occur before a crash benefits in 9 providing suitable countermeasures for said crashes. A clearer interpretation of 10 which factors interact to cause collisions allows an understanding of the mechanisms 11 that produce higher risk in specific situations in the roadway. 12Real world in-depth crash data provides detailed data which includes human, 13 vehicular and environmental factors collected on site for crash analysis purposes. 14 This study used macroscopic on-scene crash data collected in the UK between the 15 years 2000 -2010 as part of the "Road Accident In-depth Study" to analyse the 16 factors that were prevalent in 428 powered two-wheeler crashes. 17A descriptive analysis and latent class cluster analysis was performed to identify the 18 interaction between different crash factors and develop PTW scenarios based on this 19 analysis. multiple vehicle crashes. Results identified seven specific scenarios, the main types 21 of which identified two particular 'looked but failed to see' crashes and two types of 22 single vehicle PTW crashes. In cases where the PTW lost control diagnosis failures 23 were more common, for road users other than the PTW rider detection issues were 24 of particular relevance. 25 Keywords 26Powered two-wheelers, Human behavior, Human functional failure, Crash causation 27

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