Elevated ozone concentrations are frequently observed at the northern and eastern suburbs of the Athens basin. In that case the public must be informed and in addition specific suggestions are given in order to reduce transport and supply of fuel-carrying tanker trucks.

Mainly due to the none-obligatory character of these suggestions and the complex meteorology and emissions pattern at the huge Athens territory there is no clear view on the effectiveness of these measures.

In the centre of Athens municipality area, there is the "ring" where private car-circulation is regulated in relation to the last digit of the number plate (odd/even number). Since the beginning of the 80s the measure remains in force all year, except during the month of August, on working days from 5.00 to 20.00 (15.00 on Fridays). The ring has an area of approximately 10 km2.

The number plate measure is not related to ozone ambient concentration levels, but mainly aims to reduce primary pollutants in the centre of Athens. Preliminary studies have not clearly shown a relationship between this measure and the ozone concentrations.