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What's all the green paint about? Bike boxes: what they mean and how to use them
A bike box is a colored area at a signalized intersection that allows bicyclists to pull in front of waiting traffic. Designed to be used only at red lights, the box is intended to reduce car-bike conflicts, increase cyclist visibility and provide bicyclists with a head start when the light turns green.
Of particular concern is the “right hook” collision that can happen when drivers turn right as a bicycle starts straight through an intersection. In the U.S., right hook collisions are implicated in 4.7% of bike crashes, 11% of which are fatal, and 3.6% are Right Turn On Red collisions, of which 6% are fatal .
Bike boxes have been shown to be most effective when paired with a brightly colored bike lane that extends through the intersection, to remind motorists that cyclists may be traveling straight.
They can also be used to help people on bikes make two-stage left turns on wide, multi-lane streets from a right-side cycle track or bike lane, or right turns from a left side cycle track or bike lane.
The typical international best practice is a two-stage turn (also referred to as a hook turn, box turn, or Copenhagen left). Two positions are available for queuing boxes, depending on intersection configuration.
Image and content from NACTO Cities for Cycling Design Guide
On right side cycle tracks, bicyclists are often unable to merge into traffic to turn left due to physical separation, making the provision of two-stage left turns critical in making these facilities functional. The same principles for two-stage turns apply to both bike lanes and cycle tracks.
While two stage turns may increase bicyclist comfort in many locations, this configuration will typically result in higher average signal delay for bicyclists, due to the need to receive two separate green signal indications (one for the through street, followed by one for the cross street) before proceeding.
Bike boxes are called “advance stop lines” in Europe and Asia, where this safety device was first employed. The concept is now gaining popularity in cities in the U.S.A.
In most cases, the bike box is a 14-foot wide rectangle marked in front of the stop line for motorists, but behind the pedestrian crosswalk. The box typically extends the width of one or more travel lanes and provides room for several bicyclists. Bike boxes are also often used in conjunction with bike lanes, from which bicyclists pedal directly into the box. The boxes have no intended function when traffic is already in motion.
Bike boxes work best at intersections with a high volume of bicyclists. They improve cyclists' visibility. They reduce delay for cyclists by providing space for "jumping the queue" of waiting vehicles. They allow a left-turning bicyclist to reach a better position for making a safe turn. They allow bicyclists to reduce exposure to vehicle tailpipe emissions, and are also thought to elevate the "status" of bicyclists relative to motor vehicles.
Often when the bike box is employed, bicyclists are allowed to turn right on red, but motorists are not. This reduces the risk of the "right hook" collision. On one-way streets, a bike box and bike lanes can be employed on both sides of the roadway. Bicyclists on the left side can use the bike box to move safely to the right side before making a right turn.
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Additional content from the National Association of City Transportation Officials, or NACTO, from the Cities for Cycling Design Guide
In this video from New York, a cyclist demonstrates what a bike box is (and isn't).