In the United States, an "expressway" is defined by the federal government’s Manual on Uniform Traffic Control Devices as a divided highway with partial control of access. The difference between "partial" and "full" access control is that expressways may have a limited number of driveways and at-grade intersections (thus making them a form of high-speed arterial road), while access to freeways is allowed only at grade-separated interchanges. Expressways under this definition do not conform to Interstate highway standards (which ban all driveways and at-grade intersections) and are therefore usually numbered as state highways or U.S. Highways.