It is the innermost of the three beltways in the Helsinki capital region, numbered as regional route 101 and runs from the easternmost part of Espoo to Itäkeskus in eastern Helsinki.

It is primarily intended for local traffic—before the large road numbering change in the 1990s and the reconstruction of Ring III, Ring I was also designated as a bypass for avoiding Helsinki centre.

Ring I has at least two lanes per direction for its entire length but a speed limit that never exceeds 80 kilometres per hour (50 mph) owing to heavy traffic.

With the introduction of new grade-separated interchanges, provisions have been made to increase the speed limits to 70–80 km/h[clarification needed].

However, the road was not originally constructed as a motorway, which limits its capacity.