It runs from Munkkiniemi in Helsinki to the VI District of Turku, and is part of the European route E18.

The first portion of the motorway was constructed in the 1960s between central Helsinki and Kehä III, and extended to Lohjanharju in the 1970s.

In the other end of the road, the motorway stretches from eastern Turku to Lahnajärvi near Suomusjärvi.

In 2005, a portion of motorway between Lohjanharju and Lohja was opened.

This part of motorway contains five tunnels totalling 5.2 kilometres (3.2 mi).