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In order to use a bicycle safely on public roads, which is the most common bicycle facility available, it’s important to understand the leading causes of bike crashes and learn how to avoid them or minimize the chance of them occurring.

John Ciccarelli, an experienced League Cycling Instructor (LCI) with a long resume in bicycle transportation, produced instructional material for fellow LCI’s several years ago, including the first two of the three following pie charts which address the subject of bike crashes.

The first pie chart below shows the relative importance of different causes of bicyclist crashes, based on a 1976 study by Kaplan. (Please click any figure to enlarge it.)

Kaplan's 1975 study: Leading causes of urban adult bicycle crashes

The first important conclusion to draw from the above is that falls involving only the cyclist are the most common cause of bike crashes, and can be avoided by learning good bike handling techniques, plus understanding the causes of solo crashes and taking avoiding action.

For example, don’t ride in or near the gutter, which is where you may encounter wheel-grabbing drains, uneven surfaces or joints in the road, or debris which can cause a fall, swept there by car tires.

Ride either in the right car tire track, or near the center of the lane where you are most visible and you can also control the lane. If you share the lane because you feel it’s wide enough to do so, stay well away from the curb or road edge.

The second pie chart focuses on car-bike crashes and how to avoid or minimize them.
Adult urban car-bike crash causes and avoidance

Note that, in this chart, the two leading causes of crashes for which the motorist is responsible are:

1) Oncoming left turn – In which an oncoming motorist turns left across the cyclist’s path;

2) Right hook – Where a following motorist passes the cyclist and then immediately turns right across the cyclist’s path.

Both are due to misjudgement (or occasionally aggressive behavior) on the part of the motorist, who underestimates the cyclist’s speed, or because the cyclist is obscured by another motor vehicle.

A prime example of the latter is when two or more oncoming motorists are waiting to turn left at an intersection and the cyclist is following behind a platoon of cars which has already cleared the junction. Once the last of the cars has cleared the intersection the lead oncoming motorist, correctly judging he has time to cross in front of the cyclist, turns left safely but the following motorist, from whom the cyclist is hidden by the first car, doesn’t see the cyclist until he already starts to turn. At that point, the motorist and cyclist may be on a collision course, as illustrated below.

Left hook car-bike collision scenario

Avoidance techniques are: Lane positioning, emergency braking, and quick turn, the last being the most difficult maneuver to perform successfully.

In addition, almost half the causes of car-bike crashes can be avoided by the cyclist changing his or her behavior, such as not riding on the sidewalk, or the wrong way in the road.

For comparison, below I’ve added a figure showing a set of pie charts produced by LCI Dan Gutierrez based on different data, which draw the following similar conclusions to the two pie charts above:

1) The overwhelming majority of bicycle crashes don’t involve a motor vehicle;

2) Crossing Movements at intersections and driveways are the primary cause of car-bike crashes, not mid-block parallel movements.

Pie charts of Crash Risk vs Cyclist Behavior


Figures from the Street Skills Instructor Package teaching product by John Ciccarelli, LCI #453, of Bicycle Solutions,
E-mail: johnc – @ symbol –

League Cycling Instructors Dan Gutierrez and Brian DeSousa, from Long Beach, Ca., have produced both excellent slide presentations and videocam videos about the fundamentals of bicycling transportation and good bicycling techniques.
The above figure “Behavior vs Crossing Crash Risk” is slide 14 from Integrated Traffic CyclingTM Introduction. This is one of several comprehensive slide presentations at Cyclist View.
Also check out InnerTube tm to view “The Rights & Duties of Cyclists“, T=4:20 min.

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