The World Bank has sponsored a project to curb air pollution through public transport improvements and the Mexican government has started shutting down polluting factories. They have phased out diesel buses and mandated new emission controls on new cars; since 1993 all new cars must be fitted with a catalytic converter, which reduces the emissions released. Trucks must use only liquefied petroleum gas (LPG). Also construction of an underground rail system was begun in 1968 in order to help curb air pollution problems and alleviate traffic congestion. Today it has over 201 km (125 mi) of track and carries over 5 million people every day. Fees are kept low to encourage use of the system and during rush hours the crush is so great, that authorities have reserved a special carriage specifically for women. Due to these initiatives and others, the air quality in Mexico City has begun to improve, with the air becoming cleaner since 1991, when the air quality was declared to be a public health risk for 355 days of the year.[citation needed] COUNT 5
QSN1 What do new cars in Mexico need to have? ANS1 catalytic converter QSN2 When did the underground rail system begin construction? ANS2 1968 QSN3 How many people ride the Mexico city subway system each day? ANS3 5 million people QSN4 How many days of the year in 1991 was the air pollution a serious health risk? ANS4 355 QSN5 What is one way the government helps with the "Crush" of the rush hour riding of the subway system? ANS5 reserved a special carriage specifically for women