Defining daily capacities for the purpose of road planning in the Republic of Serbia

In every edition of the Highway Capacity Manual (HCM) until 2016, three levels of capacity analysis were defined: operational, project and planning analysis. The level of detail of each analysis is a function of purpose, breadth of access and available information. Planning analysis determines capacity in the earliest stages of planning, when small amount of data and information is available. The planning procedure is based on the AADT forecast and macro traffic simulation. Often, the usage of simulation models can lead to errors, and for these reasons, when analyzing traffic demands, it is necessary to carry out a check when more informations are available. Planning analyzes from the HCM manual are generally focused on broad issues such as initial problem identification, road design concept, and when alternatives are compared. These analyzes are suitable for evaluating proposed system measures, such as heavy vehicle lane usage control, highway ramp metering, and other applications of intelligent transportation systems. The methodology recommended in HCM implies the use of default input values, i.e. table of generalized values. Given that the recommended capacity values are based on typical road profiles and traffic flow characteristics in the USA, the paper provides a detailed capacity analysis at the planning level for local conditions - four standard geometric two-lane and highway profiles. Capacities are calculated for different values of design hourly volume, design speed, peak hour factor, commercial vehicle impact and terrain type, in order to compare with the generalized capacity tables from HCM2010. The comparative analysis indicates differences in the calculated capacity values, and for that reason the obtained values are recommended for use in model simulations for local conditions in the Republic of Serbia.