Siirtelys

Siirtelys are a type of slip road or on-ramp in a single-carriageway road network, typically found in Finland and other parts of the world where freight and passenger traffic is transported over long distances by rail and road. These intersections are designed to facilitate the safe and efficient transfer of traffic between lanes.

The primary purpose of a Siirtelys is to guide slow-moving traffic, including trucks, buses, and emergency vehicles, into the traffic stream, while allowing faster-moving traffic, such as passenger cars, to bypass the slower traffic. This is achieved through the use of a transition zone or "merge" area where traffic flows are managed.

A Siirtelys typically consists of three components: an approach lane where slower traffic moves, a merge lane where faster traffic bypasses the slower traffic, and a transition area or "kissing point" where the two streams meet. The design of a Siirtelys takes into account factors such as traffic volume, road geometry, and safety considerations to minimize congestion and conflict between traffic streams.

The effectiveness of Siirtelys has been studied in various research projects, which have shown that they can significantly reduce the number of accidents and congestion at single-carriageway intersections. However, their implementation requires careful consideration of a range of factors, including traffic volume, road geometry, and local driver behavior.