How is capacity determined for multilane highways?

Multilane highway capacity per lane is approximately 2200 pc/h/ln under ideal conditions. Capacity adjusted for lane width, lateral clearance, median type, and access point density. Free-flow speed (FFS) = base FFS - adjustments for lane width, lateral clearance, median type, and access density. Density = flow/speed used to determine LOS. LOS A-E thresholds based on density (11, 18, 26, 35, 45 pc/km/ln). HCM Chapter 12 provides detailed methodology including passenger car equivalents for heavy vehicles.