Mexico City is one of the biggest cities in the world.There are no trains or high-speed busesand there isn't a metrosystem, so people have to drive or take old, crowded, unsafe buses everywhere.For example,  workers use car sharing or bicycle-sharing,.This way , there are fewer cars and workers feel better.In the city's Santa Fe district.There are 850000 journeys each day.Sixty-four percent of the journeys are for business reasons.First, there is a lot of pollution.