Förbifart Stockholm was supposed to relieve the pressure on the city by directing the present through traffic to the west. The majority of the 20 kilometre route was planned as a tunnel, partly below Lake Mälaren.
But according to the Road Administration, the air in the planned tunnel would hold a hundred times more dangerous particles than Hornsgatan in Stockholm, known as the street with the poorest air quality in the capital.
It is still uncertain how the time plan and the cost calculations will be affected by the air quality problems. The government gave the go ahead for the project earlier this autumn and the construction was planned to start in 2012.