A wide curb lane (WCL) is the lane nearest the curb that is wider than a standard lane and provides extra space so that the lane may be shared by motor vehicles and bicycles. These facilities can also be placed on roads without curbs and are sometimes called wide outside lanes. WCLs may be present on two-lane or multi-lane roads. A desirable width is 4.3 m (14 ft), not including the gutter pan area. Lanes wider than 4.3 m (14 ft) sometimes result in the operation of two motor vehicles side by side. However, the WCL may need to be 4.6 m (15 ft) in width where drainage grates, raised reflectors, or on-street parking reduce the usable lane width. WCLs are sometimes designated when right-of-way constraints preclude the installation of "full width" bike lanes. WCLs are sometimes put in place by re-striping, especially when a section of roadway is resurfaced, by narrowing the other travel lanes.

WCL advocates believe that these wider lanes encourage bicyclists to operate more like motor vehicles and thus lead to more correct positioning at intersections, particularly for left-turning maneuvers. A previous FHWA publication recommends WCLs in many kinds of roadway situations where most bicyclists are experienced riders.⁴ Since WCLs are a shared-lane traffic situation, they are not signed or marked like a bike lane would be. As a result, many bicyclists do not know of their existence or utility as a bicycle facility. More detail on the comfort and safety of WCLs can be found in Hunter et al., 1999, and Harkey et al., 1996.^3,5