NCFRP Report 31: Incorporating Truck Analysis into the Highway Capacity Manual
The purpose of the National Cooperative Freight Research Program (NCFRP) Report 31 project was to develop nationally accepted highway capacity and level of service techniques suitable for incorporation into the Highway Capacity Manual (HCM) that would: 1) improve transportation agencies' abilities to plan, design, manage, and operate streets and highways to serve trucks, and 2) better evaluate the effects of trucks on other modes of transportation, and vice versa. Techniques were developed for uninterrupted and interrupted flow facilities in both rural and urban conditions. Public agencies, carriers, and freight shippers were interviewed and surveyed to ascertain the criteria most important to them in determining their perceived quality of service for truck movements on public streets and highways. A level of service model was developed from these surveys and then field tested on five case studies, the results of which were reviewed by 60 freight experts from public agencies and academia.
Microsimulation models of freeway, arterial, and signalized intersection approaches with different grades, percentages of trucks, and mixes of single-unit and semitrailer combination trucks were developed and validated. The models were used to develop relationships between the percent of grade, the percent of trucks, and the mix of truck types for the purposes of estimating passenger car equivalents for use in HCM analysis procedures. The project recommended updates to the HCM to reflect the results of the research.