An individual who uses public transportation instead of their automobile could reduce their daily carbon emissions by 20 pounds a day, or 4,800 pounds annually, according to a press release issued by the American Public Transportation Association (APTA) in observation of yesterday's Earth Day.

Switching to public transit would cut a person's emissions more than using energy-efficient light bulbs, adjusting thermostats, weatherizing a home and replacing a refrigerator with an energy-efficient model combined, APTA said.

To commemorate Earth Day, a handful of transit agencies described how they are implementing green initiatives. The Massachusetts Bay Transportation Authority and Massachusetts Bay Commuter Railroad Co. will unveil two energy-efficient locomotives; Bay Area Rapid Transit is testing energy-saving, light-emitting diode lights; agencies in Seattle are launching ORCA, a regional smart card that can be used by riders of seven participating systems; and Metrolink is testing technology designed to reduce diesel locomotive emissions.