PARIS (AP) — Paris has temporarily barred half of all cars from traveling on city streets and made public transportation free for the day as it battles a peak in pollution.

Facing red-alert levels of pollution since Nov. 30, Paris City Hall said the situation poses a significant risk to residents' health. Authorities say pollution is due to weather conditions and a heavy dependence on diesel fuel.

To tackle what City Hall describes as an "exceptionally serious" crisis, Paris's Velib bike-share and Autolib electric cars were made free Tuesday, as well as the Paris metro and bus services. In addition, only cars with even-numbered plates were allowed to drive Tuesday in the French capital and its close suburbs.

City officials say it's the ninth time this year that Paris is facing a pollution peak.