Noise pollution above the maximum immission values affects well-being and represents a significant health risk. In addition to the known impact on psychological health - stress, irritation, tension - noise can also lead to physical problems such as raised heart rate and elevated blood pressure. Noise pollution results in health costs, loss of rent and reduced property prices, as lower rents are paid in noise-polluted areas. In 2005, the total economic cost of noise was thus estimated at over CHF 1 billion per year. Finally, noise levels also lead to changes in the composition of the local population: those who can afford to do so move to a quieter neighbourhood. The most significant source of noise in Switzerland is road traffic. In contrast to rail and air noise, noise due to road traffic does not only affect certain areas, but spreads a carpet of noise across almost the entire country.

During the day, some 1.2 million people are exposed to hazardous or onerous road noise and at night the figure is 700,000. 85% of these people live in cities or built-up areas.

Road noise is limited mainly by using noise abatement structures (e.g. noise barriers) or low-noise road surfaces. As an alternative, noise abatement measures have been installed on buildings in many areas (e.g. soundproof windows). The goal of noise abatement - combating noise primarily at its source - has thus not been fully realised. For this reason, the current state is assessed as negative. In addition, the majority of noise abatement measures to date have been introduced along the motorways and transport corridors. There have, however, been relatively few in inner-city areas, where the largest number of people suffer from noise pollution. In city centres there is limited space and the multiple interactions between the road and the nearby buildings as well as the difficulties of integrating noise barriers make more effective noise abatement difficult. There is a further problem in that road traffic, particularly in the centre of conurbations, continues to increase and the progress made with road noise abatement measures is thus cancelled out. For this reason, the trend is assessed as neutral. The noise abatement strategy to date was appropriate. However, it is not sufficient to completely eliminate the problem. Future noise abatement strategies should contain additional elements, e.g.:

• Those affected by noise pollution and those responsible for policy should be better informed of the noise situation in Switzerland than previously.
• Low-noise technologies should be promoted using measures that provide a market incentive for them.
• The legally established polluter-pays principle should be strengthened, e.g. using incentive systems.

Firstly, the emissions from the sources are determined in SonBase from the basic data available (basic geodata, statistical data, traffic data etc.). The propagation and resultant noise immissions are then determined in the noise module (CadnaA) by incorporating a digital elevation model. The immission limit value in the Noise Abatement Ordinance (NAO, CC 814.41) Annex 3 is definitive.