The last decade has seen bicycling rates double or triple in major metropolitan areas, helped in part by the modern consensus around what kind of on-street facilities are best at protecting and encouraging riders. While sharrows and signage have given way to protected, separate lanes, the designs of intersections – often the most stressful part of biking – still pose a major problem.
Currently being adapted from successes in Denmark and the Netherlands, the protected bike intersection is one avenue of solving that. Rather than have protected bike lanes convert to mixing zones or indicate two-step turns, both of which can be confusing for drivers and bicyclists, the protected intersection aims to reduce conflicts and keep bicyclists in a dedicated space as much as possible.
Speaking in a session at TransportationCamp DC this month, transportation planner Emily Thomason and Nicholas Smith of Richmond, Va., modeled the protected intersection design for attendees, transforming a paper, four-way layout on the carpet with the addition of curb bulbouts and a delineated, green bike crosswalks (see above photo). As a bicyclist approaches the intersection, they can either move straight through the bike crosswalk, curve right along the protected lane, or take a left by first crossing straight, then left.
The main aim of the design is to eliminate sudden conflicts between bicyclists and drivers. By moving bicyclists closer to pedestrians, the intersection operates on the idea that bike-pedestrian conflicts are much easier and safer to negotiate than bike-car ones. And while left turns will take bicyclists longer to perform, Thomason and Smith explained, the easy right turns that require no traffic negotiation will create some time savings.
Not only do the concrete islands protect people walking and biking, but they force drivers to take wider, slower, and more deliberate turns. Using a phone as a makeshift car in his diagram, Smith walked the session through the varying ways a driver can enter the intersection. The concrete islands are long enough so that a driver turning right can enter, clear the crosswalk, then make a right turn when they have a chance. Adding another paper cut-out and folding back the corner pieces, Thomason and Smith showed how the logic applies to low-traffic roundabouts, too.
In the D.C. region, Montgomery County is the only jurisdiction with a protected bike intersection in its near-term bike plans. Part of a new network of lanes in downtown Silver Spring, the intersection of 2nd Avenue and Wayne would have concrete curb cuts on each corner.
While there are only 12 in the United States now (up from zero just two years ago), Green Lane Project’s Brad Anderson notes that the intersections make safety sense as a priority for cities, as they can be applied to conventional bike lanes too, not just protected ones. Protected intersections now exist in cities such as Davis, Calif., Austin, and Salt Lake City. Just as protected bike lanes are making streets more in line with the 8-through-80 year-old-friendly biking streets, protected intersections offer a way to complete those network gaps and simplify safer biking.
Photo: Top, the paper design laid out during the TransportationCamp (photo by author). Middle, an intersection in the Netherlands (Northeastern Delft, Flickr, Creative Commons).