Chapter 16 of the 2000 Highway Capacity Manual (HCM) describes a procedure for estimating the saturation flow rate of a signalized intersection lane group. This procedure includes numerous saturation flow rate adjustment factors that are intended to adjust the base saturation flow rate such that the resulting saturation flow estimate accurately reflects conditions on the intersection approach. Unfortunately, the HCM procedure is not complete in terms of the adjustment factors offered. It does not offer factors that reflect the effect of traffic pressure, number of lanes in the lane group, or approach speed. Moreover, guidance for using its area-type adjustment factor is too subjective to yield confidence in the accuracy of the saturation flow rate estimate. Saturation flow adjustment factors reflecting the effect of population, traffic pressure, number of lanes, and speed limit were developed for this research. A procedure for using these adjustment factors was also developed. This procedure is intended to be used with the HCM or FDOT's Quality/Level of Service Handbook to estimate the saturation flow rate for an intersection. Field measurements indicate that a base saturation flow rate of 1950 pc/him is appropriate for Florida intersections.