Chapter 7, "Multilane Highways," of the 1985 Highway Capacity Manual (HCM), published as TRB Special Report 209, is based on the limited research used for the 1965 edition and extrapolation from research on other highway types, particularly freeways. Research was needed to develop information on the operating and capacity characteristics of multilane highways and to develop an improved chapter for the HCM.

The objective of this research was to confirm and/or develop operational, design, and planning procedures for determining the capacity and level of service of multilane highways---both rural and suburban. The major thrust of the effort was focused on multilane highways having four or more lanes. The research, however, also considered special multilane configurations such as three-lane, two-way operation (2-1 split) and the provision of a continuous left-turn lane.

All research has been completed. The revised Chapter 7 was incorporated into the 1997 update of the Highway Capacity Manual.