The door zone is the space in which a cyclist is in danger of getting hit by a car door. It varies depending upon the model of car one is riding by. It can be almost zero when riding by a DeLorean or much larger if one is riding by a truck.
Legal issues 
Most areas have laws that require car users to check for bicyclists before opening the door of their vehicle, but there still have been a small number of serious injuries and deaths caused by drivers carelessly[neutrality is disputed] opening their doors when a cyclist is passing by without regard for the presence of bicycles.
Many areas have laws allow cyclists to ride in the door zone, sometimes these laws typically have exceptions, avoiding hazards is sometimes among them.
The problem lies with avoiding this 1.2m/5' zone when there is a bike lane or the perception by law enforcement or motorists that one should be riding their bike out the travel lane to not impede faster motorized traffic. In most jurisdictions a cyclists is a driver/operator of a vehicle afforded the same rights as that of the driver of a motor vehicle; however are further discriminated[neutrality is disputed] by with laws such as "ride as far right as practicable." From a cyclist's point of view, practicable includes "safely" and safety is noted in many of these laws through exceptions; however many law enforcement, judges, motoring public and even cyclists stop reading at "as far right." Most motor travel lanes adjacent to a bike lane are only 10-11' wide, so if a cyclist has to use that lane to avoid hazards in the bike lane, it is too narrow to safely share with passing traffic and should ride in a "lane-control" method as is allowed by most of these discriminatory ordinances.
Because it is rarely possible to see and react safely to a suddenly opening door, traffic cycling educational programs teach cyclists to ride in the travel lane outside of the door zone despite the fact that in one place, NYC, for example, 96% of deaths have occurred outside of the door zone.
It is difficult to find statistics on the incidence of door zone fatalities, serious injuries, and collisions as the type of accident is often not recorded consistently from city to city. However, an analysis of Chicago bike crashes found that there were 344 reported dooring crashes reported in 2011, for a rate of 0.94 doorings per day. Doorings made up 19.7% of all reported bike crashes. The number of additional doorings that occurred without being reported is unknown.
In Toronto, "motorist opens door in path of cyclist" collisions were 11.9% of all reported car/bike collisions in 2003.
Relative Risk 
Relative to other collisions such as getting rear ended, getting doored is less risky. ""80.04% of those cyclists who were doored were injured, while 94.40% of those in non-dooring crashes were injured. Also, it should be noted that getting doored itself usually was not fatal, but rather most serious door injuries were sustained by getting hit by a motor vehicle while swerving to "control the lane" or by getting run over by a motor vehicle. Thus, most actual deaths and serious injuries actually occur in the travel lane and not in the door zone.
In New York City, 3% (7 out of 225) of bicyclist fatalities in the ten-year period between 1996 and 2005 were from striking an open door or swerving to avoid one.
See also 
- "No person shall open the door of a vehicle on the side available to moving traffic unless it is reasonably safe to do so and can be done without interfering with the movement of such traffic..." CA CVC 22517
- ...(vii) a lane that is too narrow for a bicycle and a vehicle to travel safely side by side within the lane UCA 41-6a-1105
- "Layout 1" (PDF). Retrieved 2013-05-08.
- September 28, 2012 (2012-09-28). "Doorings in Chicago and NYC are still a sorry state but one of them is doing something about it". Grid Chicago. Retrieved 2013-05-08.
- "City of Toronto: Transportation Services". Toronto.ca. Retrieved 2013-05-08.
- The "Door Zone" includes instructive diagrams.
- The Door Zone Project
- Door Zone Avoidance Preston Tyree, recently retired Education Director at League of American Bicyclists, teaching LCI (instructor) candidates how to teach about the door zone.
- Why You Should Avoid the Door Zone Video showing how bicyclists are thrown into traffic when they collide with an opening car door.