U.S. Department of Transportation
Federal Highway Administration
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Here is a brief description of different route types. More detail including photographs illustrating these route types are available in the User Guide.
Limited Access Freeway – This route type includes U.S. and state numbered freeways and expressways and Interstate routes where access to and from the facility is limited to interchanges with grade separations. These high-speed routes typically have posted speed limits ranging from 55 mph in urban areas to 75 mph in some rural states. Some urban areas may have short segments directly connecting the freeway to surface streets where the posted speed limit is as low as 35 mph. Examples of a limited access freeway can be found here.
Road Section in Undeveloped Area – An undeveloped area is generally an area where the human population is low and the roadside primarily consists of the natural environment. Access is not restricted and posted speed limits are typically in the 40 mph to 65 mph range depending upon terrain and road design features. Road sections with lower speed limits usually have narrower pavement widths, little or no shoulders, and horizontal and vertical curvature that limits driver speeds. Road sections with higher speed limits usually have 12-foot lanes, 8-foot or greater shoulders which may be paved, and horizontal and vertical curvature that supports higher speed travel. Examples of a road section in an undeveloped area can be found here.
Road Section in Developed Area – A developed or built-up area is an area where the human-built environment has generally replaced most of the natural environment. Access is not restricted and posted speed limits are usually in the 25 mph to 50 mph range depending on the degree of human activity that interacts with vehicular travel, the road design, and degree of traffic control used. Road sections with lower speed limits are found in downtown and residential areas with considerable pedestrian and other non-motorized movements and on-street parking activity. Road sections with higher speed limits have little pedestrian activity, no on-street parking, and traffic control which favors through traffic movement. Roads in developed areas are further subdivided into residential subdivision/neighborhood street, residential collector street, commercial street, and a street serving a large complex such as a large shopping mall. Examples of a road section in a developed area can be found here.
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