The Eiffel Tower is seen from the Montparnasse Tower, as Paris suffers a pollution spike.

For the third consecutive day, Paris authorities have announced a ban on half of the cars entering the city centre and have made public transportation free as the city struggles with exceptionally high levels of smog.

Similar measures to tackle air pollution will also be introduced for the first time in the cities of Lyon and Villeurbanne.

Only vehicles with an even-numbered plate and carpooling services are allowed to drive in Paris centre and in 22 communes in the inner suburbs. Anyone disobeying this rule will be fined €35 ($38), with 1,700 fines handed out on the first day alone.

Airparif, the observatory of air quality in the Île-de-France region, said the pollution index reached 91 micrograms per cubic meter on Wednesday and is expected to slightly decrease to 89 on Thursday — still way higher than the warning level of 80.

This is the fourth time in 20 years that alternating traffic patterns have been introduced in the capital, but the first time they’ve been held for several days.

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.

Airparif says the peak is due to the accumulation of pollutants because of anticyclonic conditions.

The situation poses a significant risk to residents’ health, according to Paris City Hall.

Paris Mayor Anne Hidalgo has pledged, along with three other major cities, to ban all diesel cars by 2025.

“Today, we also stand up to say we no longer tolerate air pollution and the health problems and deaths it causes – particularly for our most vulnerable citizens,” she announced. “Big problems like air pollution require bold action, and we call on car and bus manufacturers to join us.

The Associated Press contributed reporting.