Preliminary safety assessment of polish interchanges

Interchanges are a key and the most complex element of a road infrastructure. The safety and functionality of interchanges determine the traffic conditions and safety of the entire road network. This applies particularly to motorways and expressways, for which they are the only way to access and exchange traffic. A big problem in Poland is the lack of comprehensive tools for designers at individual stages of the design process. This applies to guidelines or other documents regarding the location, choice of interchanges type and selection of design parameters. This does not provide sufficient material for designing safe and functional interchanges. This situation results in numerous hazards that occur on existing interchanges and errors that are still being made at all stages of the design process. Consequently, there is a risk of accidents in the area of interchanges, which often have serious consequences. The purpose of the research presented in the article is to identify main groups of hazards on the interchanges and to classify them based on field tests and audits of project documentation. The prepared classification uses the results of analyzing data on road accidents. As part of the research, a database was built that includes information on road accidents and traffic, as well as data on all existing interchanges on motorways and expressways in Poland. These data includes: interchange type, length of exit and entry lanes, total interchanges length, type of cross-section on main roads and ramps. The number and type of ramps occurring at a given interchange as well as the type of intersections, if any, were also taken into account. Based on the assessment, the level of safety was determined for individual types of interchanges. Then, the impact of selected road and traffic factors on safety was presented. The critical elements of interchanges are entries, exits, weaving sections and intersections. Assumptions were also adopted for the classification of identified hazards. A comprehensive safety assessment for interchanges allowed the development of assumptions for their design guidelines. On the basis of database exploration and field research, the main problems and hazards regarding the functioning of interchanges were identified.