Paris city hall has barred half of all cars from travelling and made public transportation free for a third consecutive day. A similar scheme will be implemented in the city of Lyon Friday.

Only vehicles with even-numbered plates are allowed to drive Thursday in the French capital and its close suburbs.

The ban was not respected by many drivers Wednesday, while disruption in transportation services added to confusion. To tackle the crisis, Paris' Velib bike-share and Autolib electric cars will again be free Thursday, as well as the Paris metro and bus services.

The body in charge of monitoring pollution says the peak is due to the accumulation of pollutants because of anticyclonic conditions.