Watch planner Jeff Speck explain how four different road diet strategies might work. Here is an example of one approach:
40-footer lane insertion
This time we focus on a 40-foot street with two 12-foot lanes of opposing traffic and two parking lanes at the curb. Many cities have adopted 12-foot lanes with the assumption that they move more traffic; in fact, as Speck has argued at CityLab before, they present a major safety hazard for cities by encouraging faster driving. He recommends slimming them down to 10 feet—a design configuration that leaves room for a bike lane and makes the street safer, even as it more or less preserves traffic flows.
This is a reminder of some of the paradoxes of road design. Provide bigger lanes and more lanes and cars tend to drive faster and traffic increases. Narrow the lanes and drivers have to slow down and pay more attention, leading to improved safety. And all of this might actually free up space for other uses – like bike lanes or more pedestrian space.
If you want more on such techniques, read Speck’s Walkable City.