Puijo highway tunnel

The highway tunnel of Puijo in Kuopio, Finland is the first road tunnel in the world specifically meant to reduce the amount of land needed for transportation infrastructure in urban areas.

Background
Kuopio, located on a peninsula in the middle of Lake Kallavesi, has long been a difficult bottleneck from the perspective of land traffic.

In the 5th century AD, a town was founded in Toivala, on the northern coast of the lake. The town, as well as the peninsular town Tavisalmi, prospered to the extent that north-south traffic on the lake increased enormously. Combined with traditional west-east traffic along the length of the lake, the result was congestion and accidents with boats sinking. Eventually is was decided to make a series of bridges to connect Toivala to Tavisalmi.

In the 1950's, the problem of congestion had shifted to the ancient Tavisalmi town center. While upgrading of road bridge over Lake Kallavesi to a 6-lane highway was underway, it was understood that no wider than 4-lane-freeway would fit between the lake shore and the protected town center (afterwards a World Heritage Site). No interchanges could be used on such a road.

The area adjacent to Kuopio city center was largely built with unefficiently low flats during the early 20th century, which made residential capabilities on the peninsula low. In 1949-1952 a section of the Main Road 5 was built as a 4-lane freeway west of the city center. The project was widely criticized for claiming a half of the park traditionally separating the old town and former rural municipality.

The possibility of a tunnel was first discussed on official level in 1960. In just a few years, it was realized that the State Road Traffic Agency (Tieliikennelaitos) would be only a minor financial sponsor. Therefore the tunnel project was made subject to a municipal referendum: the project was approved by 55% of the electorate.

Construction
The tunnel plans were finalised in 1965. The tunnel was to have its southern end between the small lakes Neulalampi and Leväsenlampi 6 km southwest of city center, and northern end on Lake Kallavesi shoreline near Tavisalmi, 5 km north of Kuopio city center. The tunnel had a major portion of it beneath Puijo Ridge. Construction was started in 1968 and the tunnel was opened in 1979. The project cost a billion in year 2008 dollar equivalent.

Phase II
In 1990 a new tunnel was approved to go in east-west direction from Telkkistenlahti Bay to a busy road named Mannerheimintie west of the Puijo Ridge, connecting the new Vaajasalo Freeway Bridge with the original tunnel. Construction commenced in 1992 and was finished in 1999.

Phase III ?
A new part of the tunnel has been discussed. It would run from Neulaniemi Peninsula beneath, the hilly area of Neulamäki, connecting to the original tunnel and then continuing into the city center, coming up at Puistokatu Street, being a continuation of Kirkkokatu Street.

If approved, phase III will be ready in 2020 at earliest.

Layout
Original tunnel
 * 0.0 km, going underground, interchange of Kolmisoppi and Levänen
 * 2.9 km, interchange of Särkiniemi, Siikalahti and Neulamäki, possible future interchange of Phase III tunnel
 * 4.1 km, interchange of Niirala
 * 5.6 km, interchange of Phase II tunnel
 * 8.8 km, interchange of Tavisalmi and Päiväranta, coming to ground level

Phase II tunnel
 * 0.0 km, going underground, end of the Vaajasalo Freeway Bridge
 * 1.3 km, interchange of Kelloniemi and Mannistö
 * 2.7 km, interchange of the original tunnel
 * 3.4 km, coming to ground level, crossing of Mannerheimintie near Rypysuo

Phase III tunnel, current discussed version
 * 0.0 km, going underground, crossing of Tervaruukintie near Pöyrynlahti
 * 1.0 km, interchange of Pieni Neulalampi
 * 4.3 km, interchange of the original tunnel
 * 4.8 km, partial interchange of Haapaniemi and Siikalahti (allowing only westbound entering the tunnel and eastbound exiting)
 * 6.1 km, coming to ground level, crossing of Puistokatu, Kirkkokatu begins.