In the Highway Capacity Manual (HCM), passenger car equivalents (PCEs) are used to convert a mixed-vehicle stream into an equivalent passenger car stream. The 2000 edition of the HCM reports PCEs for basic freeway segments as a function of the proportion of heavy vehicles, grade section steepness, and grade section length. These PCEs are reported for a typical truck with a weight-to-power ratio of 76 to 90 kg/kW (125 to 150 lb/hp). The HCM procedures are extended by using INTEGRATION software to develop PCEs for a broader range of vehicle weight-to-power ratios. In addition, the effects of pavement type and condition, truck aerodynamic treatment, number of freeway lanes, truck speed limit differential, and level of congestion are considered in the development of these PCEs. The calculation of PCEs for multiple-truck weight-to-power ratio populations is also examined and found to be not significantly different from PCE factors for single-truck weight-to-power ratios. The PCE values are tabulated in a format compatible with that used in the HCM 2000 capacity and level-of-service procedures.