Abstract The World Bank Highway Development and Management (HDM-4) tool has been used extensively for the management of road networks, particularly in developing countries. The paper describes the application of HDM-4 model for local roads in Bosnia and Herzegovina (BiH), in the Herzegovina-Neretva Canton (HNC). The HDM-4 study was performed with the aim to define road works program and investment priorities by analyzing impacts of different budgets on future network condition. The 396 km-long HNC road network consists of 13 roads that are either graveled or paved. A large part of these roads do not have sufficient pavement width. This road network is in relatively poor condition due to its age (the average age is over 30 years) and limited spending on maintenance in the past. Only a small percentage of the network has been reconstructed in recent years. The Average Annual Daily Traffic (AADT) has a wide range, and varies from 27 to 12735 vpd. The major challenge in the study was to obtain HDM-4 input data with limited resources, since usually this task requires extensive investigations. In addition to inventory data, it is necessary to define the condition of the road network, traffic volume, traffic data, etc. Road geometry data were obtained from previous studies and project documentations. The IRI data were taken from the earlier surveys or estimated where no data were available. Other parameters were obtained by field tests. Traffic data were available from regular network traffic counts. After analyzing the parameters, the network was divided into 65 homogeneous sections, based on the AADT and road condition (IRI and other parameters) classes. HDM-4 program analysis was performed for a period of 30 years. Due to very low traffic loading and relatively large investment needed for improvement, for majority of sections a negative NPV and IRR were obtained for maintenance alternatives other than routine maintenance, and for significant number of sections they were on the verge. Out of 65 homogeneous sections, only 29 sections proved cost-effective (NPV/CAP ratio is positive). The implementation of developed road work programs would result in a substantial improvement of the overall network condition. The IRI of paved road network would change from current value of 4.5 m/km to 4.0 m/km and 3.7 m/km for budget levels of 2.0 and 3.0 mill. BAM after five years. The better road network condition would also result in improved traffic safety, social and economic impacts, since many of these roads are crucial links in the HNC.

Free flow speed is used as a parameter in transportation planning and capacity analysis models, as well as speed-flow diagrams. Many of these models suggest estimating free flow speed according to measurements from similar highways, which is not a practical method for use in B&H. This paper first discusses problems with using these methodologies in conditions prevailing in B&H and then presents a free flow speed evaluation model developed from a comprehensive field survey conducted on nine homogeneous sections of state and regional roads.

The paper presents a comparison of the possibility and complexity of the calibration process of two microsimulation models. The first model CORSIM is simple for use while the second named S-Paramics is more complex software. For research purposes, a model of street network with defined geometry (number, width and purpose of lanes) has been made. The volume and distribution of traffic as well as the data about traffic signals were input in the models. Numerous simulations were performed, first with the default parameters of models, and then with the calibrated parameters. Both programs have resulted in very good prediction of the intersection capacity and discharge volumes. However, for the calibration of speed more time and effort have been made in S-Paramics in which the average speed may be higher than the defined free-flow speed. This can present a problem in determining the level of service and comparing the S-Paramics results with other simulation models and analytical method results. On the other hand S-Paramics has greater capabilities than CORSIM (roundabouts modelling, dynamic traffic assignment, opportunity to interact with traffic signals...). Thus, for each specific task, one should carefully choose an appropriate program which would result in necessary and reliable output data with minimum effort and time consumed.