According to the National Highway Traffic Safety Association (NHTSA), in 2013, compared to passenger car occupants, mile for mile, motorcyclists are 26 times more at a fatality risk in crashes. More specifically, North Carolina was ranked 4th in the US with respect to the total motorcycle fatalities. Due to the different nature of crashes and their causes, several previous studies affirmed to distinguish single-vehicle motorcycle crashes from crashes involving other vehicles. Notably, the severity of motorcycle crashes is highly associated with the number of vehicles involved. Moreover, other pillion passengers of the motorcycles are expected to influence injury severity. Given these facts, this paper provides useful insight into single-vehicle, single-rider motorcycle crash injury severity in an effort to develop effective strategies and countermeasures. To do so, this paper, as the first of its kind, takes advantage of the partial proportional odds (PPO) model to analyze Highway Safety Information Systems