Eritasoliittymä

Eritasoliittymä, or eritasoliittymä in Finnish, is a grade-separated intersection where two or more roads cross at different vertical levels to allow through traffic to bypass at-grade crossings. This arrangement aims to improve traffic flow and safety on highways and major corridors by eliminating cross street conflicts and reducing stop-and-go conditions for through movements.

Key components of an eritasoliittymä include ramps for entering and leaving the through roads, overpasses and underpasses, and often additional features such as service roads, acceleration and deceleration lanes, and appropriate signage and lighting. The grade separation allows higher speeds on the main routes and smoother merging with incoming traffic.

Common configurations are diamond interchanges, cloverleaf interchanges, stack interchanges, turbine interchanges, and various partial forms. Each configuration uses a different pattern of ramps and bridges to route traffic between the intersecting roads while keeping the main roads free of at-grade conflicts. The choice of layout depends on factors such as traffic volumes, available land, and the desired level of mobility versus land use.

Advantages of eritasoliittymä include reduced collision risk, higher capacity for through traffic, and smoother flow during peak periods. Limitations involve higher construction and land costs, more complex engineering, and longer approaches that can affect local access and weave movements if not carefully designed.

In Finland and other European countries, eritasoliittymät are common on motorways and major arterials, built to national design standards and integrated with surrounding road networks. They reflect the shift toward high-capacity, grade-separated road infrastructure in modern traffic systems.