{"id":384,"date":"2012-12-20T19:46:18","date_gmt":"2012-12-21T01:46:18","guid":{"rendered":"https:\/\/iamtraffic.org\/?p=384"},"modified":"2018-08-12T16:45:18","modified_gmt":"2018-08-12T22:45:18","slug":"behaviors-and-risk","status":"publish","type":"post","link":"https:\/\/iamtraffic.org\/engineering\/behaviors-and-risk\/","title":{"rendered":"Bicyclist Behaviors & Crash Risk"},"content":{"rendered":"

Successful bicyclist behavior is driven by knowledge of common crash types and the behaviors needed to successfully avoid those crash types.  Bicyclist behavior comes in a spectrum with three main behaviors, and in this article we aim to briefly describe the spectrum and show how those behaviors fare in common crossing conflict crash scenarios with diagrams and supportive video.
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There are three types of bicyclist behavior:<\/h4>\n

Pedestrian behavior
\n<\/strong>Avoiding the roadway by using paths, sidewalks\/crosswalks, often against traffic flow<\/p>\n

Edge behavior
\n<\/b>Operating at the roadway edge or close to parked cars, includes shoulder and edge bike lane use<\/p>\n

Driver behavior
\n<\/b>Following the rules of the road by using roadway through lanes and turn lanes as an equal driver<\/p>\n

\"Cycling<\/p>\n\n

The behavior descriptions above meant to describe behavior at a particular place and time, not people, since a cyclist for example who prefers to engage in driver behavior on normal roads, may be required by law to engage in edge behavior in an edge bike lane.  When operating on a crowded shared use path that is away from roads, with high pedestrian volumes, that same cyclist who would prefer driver behavior, may have no choice but to use ped behavior to avoid crashes.  So it is not uncommon for cyclists to engage in multiple behaviors on a single trip.<\/p>\n

This is why we don\u2019t talk of edge cyclists, though a cyclist may be edge riding on a particular facility, and similar for driver and ped behavior.  It is also important to understand that unlike edge and ped behavior, driver behavior is a learned behavior that must be taught; it is not innate.  So just because a bicyclist who may at present prefer the more common edge or ped behaviors, does not mean that they will never learn driver skills and\/or engage in driver behavior, so we recognize that behaviors are not in general fixed and can change over time and exposure to skills training.<\/p>\n

The value in identifying behavior, instead of cyclists themselves, is its descriptive power in identifying how behavior influences crash likelihood and why some behaviors are more successful than others in an urban environment with driveways and intersections, the places where most cycling crashes occur.  The most common types of crashes are referred to as crossing crashes, where the paths of a turning motorist at a driveway or intersection and a straight through cyclist can potentially cross, creating conflicts and crashes.  Because of this, we often refer to driveways and intersections as crossing conflict areas.<\/p>\n

\"Crash<\/a>The pie chart couplet (right) shows that even though car-bike crashes comprise the minority of cases where bicyclists hit the ground, when expanded to a full pie (at the right side), the crossing crashes comprise about 5\/6 of the total number of crashes.  In examining these crossing crash types, we can learn a great deal about behavior and the facilities and laws that enable or restrict behaviors, influence how successful cyclists will be at negotiating urban roads.<\/p>\n

Crossing Conflict Types<\/h3>\n

Let\u2019s examine the three main crossing conflict types and the effect of bicyclist behavior. The three types are pullout, left cross and right hook. These conflicts occur at driveways and intersections. We’ll examine each individually.<\/p>\n

Pullout <\/strong><\/p>\n

(shown in the diagram at a driveway)<\/p>\n

\"Pullout<\/a><\/p>\n

A pullout occurs when a motorist leaves a driveway or turns right at an intersection and approaches a cyclist from the right side, perpendicular to the cyclist’s through line of travel, resulting in a side impact to the cyclist, or causing the cyclist to hit the side or rear of the vehicle if it turns sooner in front of the cyclist.
\nLook at the driver of the silver SUV approaching the driveway, prior to making a right turn into the street.  The driver is mainly looking to the left for road traffic, such as cars and trucks, so a bicyclist using driver behavior is more easily seen (visibility) by the SUV driver because they are operating where drivers pulling out of driveways are expecting approaching traffic to be located in the roadway.  In addition, that same bicyclist can see further down the driveway (vantage) and determine when a motorist is preparing to make a right turn.  Visibility and vantage go hand in hand when a bicyclists is further leftward in the roadway.<\/p>\n

A bicyclist using edge behavior is not where motorists expect cyclists to be, and may be visually shielded by fixed sight line obstructions such as foliage, and street furniture, or even dynamic obstructions such as peds.  Thus a motorist may not see a bicyclist at the edge and turn in front of them.  An even more difficult dynamic occurs when bicyclists are on the sidewalk engaging in ped behavior.  Here they not where motorists are expecting them to be (in the road), and are even more susceptible to visual screening by fixed and dynamic obstructions, so they have minimal visibility and vantage; the opposite of the driver behavior case.<\/p>\n

Now we need to consider that motorists about to exit a driveway or turn at intersections also look to their right.  They use this alternate scan to look for slow moving, about 2-3 mph peds on the sidewalk.  They are not expecting or looking for much faster bicyclists facing traffic on the sidewalk, or the illegal bicyclists riding facing traffic at the road edge.  So these \u201cbackwards\u201d edge and ped behaviors have even poorer visibility and vantage than their normal flow counterparts.  Notice also that there is no \u201creversed\u201d driver behavior, driver behavior skills classes teach cyclist to never operate this way.<\/p>\n

It should come as no surprise that bicyclists are more frequently injured by pullouts when operating on the sidewalk or at the road edge.  These behaviors are less successful than driver behavior in negotiating driveways and intersection pullouts.<\/p>\n

In the tabs below are video clips showing pullout scenarios.<\/p>\n

[tabs slidertype=”top tabs”] [tabcontainer] [tabtext]Video Example 1[\/tabtext] [tabtext]Video Example 2[\/tabtext] [tabtext]Video Example 3[\/tabtext] [\/tabcontainer] [tabcontent] [tab]<\/p>\n