If your commute is longer, or if gas prices rise, the savings could be even greater.
In Oklahoma City, the average commute is about 15 miles and the average car gets around 20 miles per gallon.  Therefore, the average commuter spends about 5 dollars a day in gas on their daily commute (1.5 gallons total at $3.25/gallon).  If an Oklahoma City resident were to commute to work twice a week using public transportation, he or she would save 156 gallons of gas and over $500 per year.  If your commute is longer, or if gas prices rise, the savings could be even greater.