The FHWA guidance released Tuesday is the result of two years of research into numerous modern protected bike lanes around the country, in consultation with a team of national experts.

"Separated bike lanes have great potential to fill needs in creating low-stress bicycle networks," the FHWA document says, citing last year's study by the National Institute for Transportation and Communities. "Many potential cyclists (including children and the elderly) may avoid on-street cycling if no physical separation from vehicular traffic is provided."

Among the many useful images and ideas in the 148-page document is this spectrum of comfortable bike lanes, starting with bike infrastructure that will be useful to the smallest number of people and continuing into the more broadly appealing categories:

Mark