1) Adjusting a count or estimate of the hourly volume of vehicles to account for the effects of prevailing traffic conditions. See the module "Determining Flow Rate" for information on Step One.
2) Adjusting the free-flow speed for the prevailing design conditions of that section. This module addresses the second step.
The free-flow speed of a freeway section can be obtained directly by field measurement. If field measurements are not feasible, the free-flow speed can be estimated by the following equation, which accounts for the effects of physical characteristics:
FFS = 70 fLW fLC fN - fID
The adjustment factors can be obtained from the tables below.