By comparing speed of injured riders at the time of their crash to that of riders who have safely travelled through the same site, the study can investigate the importance of speed. It is known that speed is a factor in the severity of a crash, but there is less information about the role it plays in causing a crash, and whether there is interaction between speed and other factors, like experience, age, etc.
It is important that speed measures are accurate and objective, rather than relying on recall. Speed measurement by the study team is a research activity, not an enforcement activity. When control participants are completing the questionnaire, their permission to use their measured travel speed will be sought.