The impact of reducing the maximum speed limit on motorways in Switzerland to 80km h−1 on emissions and peak ozone

Hot and dry conditions in summer 2003 led to ozone levels that substantially exceeded the Swiss ambient air quality standard. We investigated how emissions and ozone levels would have changed in this period if the maximum speed limit on Swiss motorways were decreased from 120 to 80km h^-^1. The air quality model package MM5/CAMx was applied to two nested domains, both including Switzerland. Anthropogenic emissions were based on various European and Swiss data sources. The simulations for the reference case were based on current driving behaviour. In the reduction case, nitrogen oxides (NO"x) emissions from road traffic were lower by about 4% with respect to the current total NO"x release. Emissions of volatile organic compounds (VOC) were not significantly affected. The peak ozone levels decreased by less than 1%.