The planning, designing and subsequent exploitation of a road network requires tools enabling rational decision-making with regard to the use of solutions (selection of geometry, traffic organization and management, equipment etc). Road capacity, which is one of the basic features characterising the individual elements of road infrastructure, plays a key role in the selection of a road’s cross-section and the assessment of alternative solutions. Capacity estimation is inextricably linked to the assessment of traffic performance, through which it is possible to implement a qualitative approach to the process of road design and exploitation. The HCM and HBS methodologies are geared towards proper determination of the Level of Service (LOS) measures and subsequently to capacity estimation. Two-lane highways were divided according to their functions and road cross-section, which in turn led to the establishment of several classes of road sections homogeneous in terms of longitudinal gradients and the share of heavy vehicles, as well as road curvature (HBS). The basic measures of traffic performance are average travel speed and traffic density. Different traffic performance measures in the HCM and HBS methods and different analytical methods produce disparate traffic performance assessments for a given road section. In this paper, the authors present a comparison of the sensitivity of both methods to change in road features and traffic characteristics.
Additionally, the paper describes selected studies on travel speed carried out in Poland on over 90 rural road sections in 2016-2017. It presents the research method, potential impact factors and variation of the studied road features, surroundings and traffic on travel speed. The authors conduct an analysis of interdependences between basic traffic parameters including traffic volume, speed and density in specific classes of road conditions and relate them to HBS findings. The analysis is aimed at developing a proprietary Polish method of estimating traffic performance and the capacity of two-lane highways. The research was carried out as part of a project named "“Modern methods of calculating the road capacity and assessment of traffic conditions of roads outside municipal agglomerations, including express roads” [1] within the framework of a program financed by the National Center for Research and Development and the General Directorate for National Roads and Motorways.

traffic performance, capacity, two-lane highways, research and analyses