Mexico City issued its first smog alert in 11 years, banning for 1.1 million cars from driving in the Valley of Mexico. The city passed legislation in the 1990s to restrict the use of older highly-polluting cars. However, city officials relaxed these bans to allow for industrial activities to produce at higher rates. This change has enticed more drivers from outside of the city proper to drive in for work. Roughly 5 million vehicles are registered in the city proper, but the traffic from outside residents has increased the vehicle traffic an additional 1.4 million cars per day. The effects of global warming in the Valley, which geographically designed to trap pollution between the mountains leaves Mexico City vulnerable to hazardous ozone levels. Officials have offered free bus fare to entice drivers to leave their vehicles behind. The high-pressure weather and intense sun levels contribute to this extreme high. Residents are encouraged to stay inside and avoid physical activities outdoor to avoid respiratory complications. Officials say that if levels don’t go down within the next couple weeks they will consider stopping industrial activity until the smog can clear out.