Public transportation is pretty good in Chicago. There are many subways, Metra, and bus stations all over the city. In rush hours it is better to take subway or Metra to get to the airport than any other transportation. For example, in rush hours it might take over 1.5 hours to get from the Loop to O’Hare Airport by car while Blue Line will get you there in about 40 minutes for the price close to 20x cheaper compare to taking a cab.