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  • ABSTRACT: We analyzed police crash reports involving drivers and cyclists in Portland, Oregon. Of 33 identified causes of crashes, the majority (55%) came from just three mistakes:

    • #1 Driver failed to yield while turning
    • #2 Driver failed to yield to cyclist in bike lane
    • #3 Driver failed to obey light or stop sign

    In more descriptive terms, drivers often hit cyclists while turning across a bike lane, or by failure to remain stopped at stop signs or red lights.  Focusing education and enforcement resources on these behaviors are most effective at reducing crashes with cyclists.

    Portland’s behavioral causes are similar to what is found in the literature throughout the United States.  As is a universal finding throughout the literature, Portland crashes are mostly in daylight, clear, dry conditions.

    RESULTS  If one wants to reduce driver/cyclist crashes, the graph provides the guidance on behavioral causes.  Education and enforcement should focus on the top causes, and direct attention to the bottom causes only when resources allow. The top three problematic behaviors massively overshadow the other problems.  Investing resources to tackle those three behaviors will be most effective at preventing crashes.

    Notice that the majority of crashes occur in daylight, dry, clear conditions.  This is expected, and is a universal finding throughout the literature.  It’s ineffective for education and enforcement to spend inordinate resources on telling cyclists to have lights.  It’s unfortunate (and arguably harmful) when safety programs haven’t read the data, and focus solely on cyclists having lights.

    Once a safety program has addressed the top causes, if it still has resources, it makes sense to go down the list to address the lower causes.

    Having these police reports also tells us the frequency of reported driver/cyclist crashes.  

    Reported driver/cyclist crashes occur at least an average of every 5 days.

    During pleasant weather when more people are riding bikes between June-September, reported driver/cyclists crashes occur at least an average of every 3 days.

    This high frequency of crashes represents tremendous individual and societal suffering.  Even drivers who are physically unharmed are dealing with the many consequences.