Review of methods for assessing traffic conditions on basic motorway and expressway sections

Abstract

Motorways and expressways are the core of each country’s road system. Road planning, design and management requires tools to ensure that roads have the right geometry, traffic layout and equipment. These include methods for capacity estimation and assessing traffic conditions. Because the paper focusses on the basic segments of motorways and expressways (sections located between interchanges and outside of their influence), its objective is to review and compare methods used worldwide and establish whether their assumptions or procedures could be used in Polish conditions. Four methods were selected for analysis: US, German, Swedish and Dutch. Theoretical and empirical comparisons were conducted, with the latter using data from sections of motorways and expressways in Poland collected in the RID-2B project. The results of the analyses showed important differences between the methods in terms of procedures for traffic conditions assessment, assumptions, base capacities, traffic conditions measures, factors or speed-flow models. Significant differences were also found when traffic parameter estimates made with particular methods were compared to real data from Polish roads. The results contributed to the development of Poland’s new method, to be prepared as a result of the RID-2B project. It was concluded that none of the analysed methods can be directly adopted to Polish conditions. An important conclusion is the need to include Poland-specific motorway speed limits and procedure for determining free-flow speed, the basis for further analyses.