1966 and 1970 two parts of the western link of the ring road around Stockholm city centre was opened. This link - Essingeleden - changed the traffic pattern around the central parts of Stockholm in the seventies. Outside the central parts traffic increased during the seventies with 10-20 percent and even more around the new roads. This traffic growth was applied to the roads in these parts.

Nitrogen oxides concentrations are used as one indicator of air pollution from road traffic. The contribution from the road traffic emissions to the total concentrations of nitrogen oxides in the seventies is shown in the figure above.