Contributing factors are traditionally categorized in three groups.
- Factors related to road users. In the case of PTW accidents it is useful to distinguish between factors related to the PTW rider (such as age and experience) and factors related to other road users in particular their perceptual problems.
- Factors related to the vehicle. Examples of such factors are engine performance and type of PTW etc
- Factors related to the road. Examples of such factors are quality of road surface and obstacles.