The amount of harmful atmospheric pollutants emitted by vehicles has gone down in recent years despite Swiss roads becoming busier.
The Federal Environment Office said however levels were still too high and efforts to reduce greenhouse gas emissions needed to be stepped up.
A report published on Thursday shows emissions from 1990-2010 and makes projections up to 2035. The downward trend in emissions from trucks, tourism and delivery vehicles, buses and motorbikes is expected to continue. This is due to tougher standards for vehicle exhausts and fuel quality requirements, the Environment Office said.
Levels of mono-nitrogen oxide – which reacts to form smog and acid rain - from traffic have halved since 1990 and are expected to fall by a third by 2035.
But traffic continues to produce significant levels of CO2 emissions and it is worsening as roads become busier. Around 85 per cent of greenhouse gases are emitted in the form of CO2, produced mainly from burning fossil fuels like petrol and diesel.
The report noted that short journeys were particularly harmful, as most CO2 is emitted when engines are started up and in the first kilometres of a journey.
According to the Federal Environment Office, levels of emissions from vehicles need to remain under the 14.4 million tons produced in 2010 in order to reach the 12.8 million tons target for 2030.