The relation between speed environment, age and injury outcome for bicyclists struck by a motorized vehicle - a comparison with pedestrians.

This study analyzes (a) the relation between injury severities, the age of the bicyclist and the speed environment at accident locations (mean travel speed of the traffic flow involved in the accident) where a bicyclist was struck by a motorized vehicle and (b) how these relations differ from those for struck pedestrians. Accident data from Sweden for the years 2004-2008 was used to identify accident locations to analyze the relations between speed environment, age and injury outcome. Seventy-seven accident sites were used for field measurements and further analysis. The results show that both speed environment and age have considerable correlation with injury severity. There was a statistically significant relation between injury severity and the speed environment, and large proportion of the serious bicycle accidents occur at locations with speeds below 30km/h. Also, the risk of serious injuries or fatalities seems to increase after the age of 45. To our knowledge this is the first study that uses the mean travel speed in this manner for analyzing injury severity of struck bicyclists.

Relative fatality risk curve to describe the effect of change in the impact speed on fatality risk of pedestrians struck by a motor vehicle.

Models describing the relation between impact speed and fatality risk for pedestrians struck by a motor vehicle have frequently been used by practitioners and scientists in applying an S curve to visualize the importance of speed for the chance of survival. Recent studies have suggested that these risk curves are biased and do not give representative risk values. These studies present new fatality risk curves that show much lower risks of fatality than before, which has caused confusion and misconceptions about how these new curves should be interpreted, and how this should affect speed management policy. The aim here is to deepen the understanding of the implications this new knowledge has for urban speed policies by analyzing (1) what the most reliable knowledge is for this relation today and what limitations it has, (2) how these risk curves are interpreted today, and what limitations this interpretation has and (3) what the risk curves say about the importance of speed and speed changes. This paper proposes an additional tool, the relative fatality risk curve, to help prevent misconceptions. The proposed relative risk ratios and curves show that, even though the most recent results indicate that the risk is lower than assumed by the older models, the fatality risk is still as sensitive to speed changes as before.