Causes of Bike Crashes

I recently came across data from two different sources that sheds some light on the causes of bicycle crashes.  The first is a report from the Twin Cities Bike Club of Minnesota.  The second is a report prepared by the city of Fort Collins, Colorado.  While the two sets of data covered different time periods and were compiled in different ways, they are interesting to look at.

The Twin Cities Bike Club has a Safety Committee that compiles records of all of its members’ bike crashes throughout the year.  The most recent data is from 2009.  In all, 34 crashes were reported,  and they fell into three categories:

Falling from a bike, 23; bike-bike collisions, 5; and bike-car collisions, 6.

The falls ran the gamut of causes, from silly to unfortunate.  My favorite: “Rider was drinking from camelback with one hand and braking with the other while negotiating a curve, went down.”  Other falls happened because of trouble with pedals and cleats, skidding on wet pavement, going off a paved bike trail, and handlebar grips coming loose.

Falls aren’t a laughing matter, though.  Falls can hurt.

In Fort Collins, the city’s report didn’t count falls from bikes.  It focused solely on car-bike crashes, with an eye to making the city’s streets safer for commuters.  It covers police reports filed between Jan. 1, 2007-June 30, 2009.  In all, 354 bike-car crashes were studied.  The conclusion:  Both motorists and cyclists share the blame.

The biggest cause of bike-car crashes may be considered somewhat of a surprise: Bikes traveling against traffic and ending up in a broadside collision with a car.  These kinds of crashes accounted for more than half of the fatal or severe injury crashes, and 60 percent of all crashes, in the report.  A broadside is a crash when a bike hits a car on a perpendicular road.

A broadside crash in the making.

Those of us who ride regularly might be surprised to learn that most of the broadsides happened when the bike was riding against traffic.  Part of the reason might be that Fort Collins, a city of about 140,000 people, is home to Colorado State University, which enrolls 26,300 students.  Many of these students commute to campus by bike.  The city’s bike coordinator says the crash data shows that university students could benefit from bicycle education efforts.

Other car-bike crashes included the overtaking, or “right hook” crash, where a car passes a bike, then turns right.  Those were 13 percent of the crashes.  Sideswipes, where bikes and cars were going in either the same or opposite directions, accounted for seven percent.

The Twin Cities crash data is less clear about the causes of bike-car crashes.  Only one seemed to fit the “right hook” description, and none apparently were broadsides.  Inattention by cyclists was the evident cause of some crashes: A rider was hit in a right turn lane, and another rider crashed into the back of a school bus when the bus suddenly stopped for railroad tracks.

So, what do we learn from these very different reports?  Both bikers and motorists have lots of room for improvement.  Clearly, if you ride predictably and obey the rules of the road, your chances of tangling with a car diminish.  But you must be alert and attentive all the while you are on your bike.  It’s not just the cars that can knock you down.  It’s yourself, too.


    • says

      This is really interesting info. Fortunately, I have not yet experienced any crashes (I ride about twice a week to work), but the incident descriptions serve as a great warning list!

  1. Tim says

    Ray, your numbers are right in line with what previous safety studies have shown. The percentages are so close it’s almost freaky. Check out some of the data that John Forester cites. The causes don’t seem to be changing, I wonder if the overall accident rate is improving, getting worse or remaining static.

    Only had one car-bike collision and that was completely my fault. Bullet-proof college kid syndrome.

    My last two mishaps were solo crashes. One was taking a corner too fast during a rain shower (lots of road rash). The most recent was during a turn on dry, smooth pavement (concussion, mangled hand). Still haven’t figured out how that one happened.

  2. says

    I would expect the bike club records to have a considerably lower number of incidents caused by ignorant practices (wrong-way cycling, not taking the lane, etc.), by virtue of the sample. They’re all part of a bike club, and can be expected to be less ignorant of safe cycling. Note, I said “less ignorant.” I’ve seen some ridiculous behavior by people I thought would have known better. I would also expect their reports to be more detailed, and as generally favorable towards cyclists as many police reports are towards motorists.

    Of the two studies, the Fort Collins study seems the more useful. They have the opportunity to preach to a group other than the choir, with solid information to stand on (assuming the police reports aren’t too car-biased). The numbers they gathered can be turned into a good educational plan to reduce those same numbers.

    Every day I see someone riding against traffic, or blowing across side streets and driveways while on the sidewalk. It’s just a matter of time before I witness the catastrophic results.

    The last three crashes I’ve had (of the six I’ve had in my adult life) were solo crashes caused by slick asphalt (2), and reckless speeding around a blind curve (1). Those were all in the summer of ’08. Prior to that, I had one fall in ’94 caused by taking a tight u-turn too slowly up a hill, and another that same year from hydroplaning in a deep puddle. Before that, I was in 7th grade (not quite adult), riding on a sidewalk against traffic and I hit a car coming out of a driveway broadside. That was when I knew for certain what the nagging sense of doing-it-wrong was all about. I’ve been a street cyclists since, with rare forays onto sidewalks when it actually makes sense, and reduces danger, rather than increases it.

    • says

      In fairness to the bike club members, it appears that most of the crash reports come from the bikers involved in the crashes, and they seem to be honest about what happened. Here’s a selection:
      • Riding along and got sucked off the road edge by loose gravel.
      • Ran into gravel while trying to make a turn.
      • While riding at night, hit the curb and went down.
      • On bike path, turned too suddenly try to make a turn and slipped on wet
      Yes, in most car-bike collisions, they appear to find the driver at fault:
      • Rider error — hit in right turn lane at intersection.
      • Rider hit at intersection, driver error.
      • Rider was in intersection with the right-of-way when a van entered and
      hit the rider.
      I think the club data is also useful because of its inclusion of falls. It’s a reminder to cyclists to always be alert.
      (Good to hear from you again, Dave!)

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