Kehä I (Ring I) is the busiest highway in Finland, carrying up to 113,000 vehicles per day. It is the innermost of the three beltways in the Helsinki region, running from the easternmost part of Espoo to Itäkeskus in eastern Helsinki for a total of 24.2 kilometers, of which 16 are in Helsinki. It is primarily for local traffic, before the large road numbering change in the 1990s and the reconstruction of Kehä III, it was also meant for bypassing Helsinki.
Kehä I has at least two lanes per direction for its entire length, and the speed limit never exceeds 80 km/h due to heavy traffic. With the introduction of new interchanges, speed limits have been changed (and will be changed) from 60 or 70 to 80 km/h. Eventually, all intersections on Kehä I will be upgraded to interchanges. However, the road is not constructed as a motorway, which limits its capacity.
A major modernisation project is under way at Leppävaara, Espoo, where the road is being set into a tunnel. The aim is to ease the flow of traffic in what is the worst traffic bottleneck in the Greater Helsinki region.