Three sets of adjustment factors have been provided to the user. The three factors (Universal, User, and HCM) are multiplied together to yield the saturation adjustment factor shown in the LOS Computation report.
These factors are applied by lane type universally to all intersections. They can be edited in the Options…Global Data…LOS Parameters screen.
These are user entered, movement-specific factors that can be entered using the User Saturation Adjustment screen from the pop-up Geometry menu.
These are TRAFFIX calculated movement specific factors. The data needed to compute these factors is entered using the HCM Saturation Calc Input screen from the pop-up Geometry menu. The HCM calculation of saturation adjustments can be turned off in this same screen (The default is ON). See the Highway Capacity Manual for an explanation of the input data and the computation of the adjustment factors.
Note : The HCM 1997 and 2000 methods make the MLF adjustment to the saturation flow rates instead of to the volumes, as is done in the HCM 1994 method. The adjustment rates are essentially the same, but they are applied at different stages of the calculation.
The input data and the intermediate computations are summarized in the LOS Detailed Computation Report. This report may be supplemented with a “Dual Phase Control” report if protected+permitted phasing is present. Another supplemental report, “Permitted Left Turn Sat Adj”, is generated if permitted left turn phasing is present. You can select this report and its supplements in the Options…Global Data…Reports screen. It is called LOS Base Detail and LOS Future Detail in this screen.
The Yellow plus Red time per phase (default = four seconds/phase) and the total intersection loss time are used to compute the number of seconds to be added to the actual green time to obtain the “effective” green time. The effective green time is used in the permitted left saturation flow computation for the 1994 HCM Operations Method. The total intersection loss time is divided by the number of critical phases to obtain the loss time per critical phase. The difference between: the Yellow + Red time, and the lost time per phase, (usually one second) is added to the actual green time to get the effective green time.