SATURATION FLOW RATES BY FACILITY TYPE

The definition of saturation flow rate, as defined by the Highway Capacity Manual, is the equivalent hourly rate at which vehicles can traverse an intersection approach under prevailing conditions in vehicles per hour of green or vehicles per hour of green per lane, assuming the green signal is available at all times and no lost times are experienced. The Florida Department of Transportation (FDOT) initiated a research study of saturation flow rates in five South Florida counties--Broward, Palm Beach, Martin, St. Lucie, and Indian River. The FDOT hypothesized that geographical differences in saturation flow rates existed between the five counties, which were characterized as urban to rural in nature. The FDOT collected and analyzed data to develop a database to support localized saturation flow rate assumptions in planning and traffic operational analyses. This article describes the saturation flow rate literature review, selection of study intersections, data collection, and saturation flow rate analysis. Researchers concluded that more significant variance of flow rates is exhibited by the number of through lanes per approach than by geographical differences.