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 Capacity and LOS: Professional Practice

 
Basic Freeway Section and Ideal Freeway Conditions

The following excerpt was taken from Chapter 3, page 3-1, of the 1997 revision of the Highway Capacity Manual published by the Transportation Research Board.

A freeway may be defined as a divided highway with full control of access and two or more lanes for the exclusive use of traffic in each direction.

Freeways provide uninterrupted flow. There are no signalized or stop-controlled at-grade intersections, and direct access to and from adjacent property is not permitted. Access to and from the freeway is limited to ramp locations. Opposing directions of flow are continuously separated by a raised barrier, an at-grade median, or a raised traffic island.

Operating conditions on a freeway primarily result from interactions among vehicles and drivers in the traffic stream and between vehicles and their drivers and the geometric characteristics of the freeway. Operations can also be affected by environmental conditions, such as weather or lighting conditions, by pavement conditions, and by the occurrence of traffic incidents.