Public transportation agencies across the country joined in the 41st Earth Day celebration on Friday with a variety of green initiatives and activities aimed at raising awareness and improving the environment

Currently, public transportation in the U.S. saves 37 million metric tons of carbon emissions and 4.2 billion gallons of gasoline, according to the American Public Transportation Association (APTA).

"Every day is Earth Day for the tens of millions of Americans who use public transportation. Riders not only help the environment, but save money and beat the high cost of gas. They get a two-fer," said APTA President William Millar. "Public transit could play an even larger role, but unfortunately, only 54 percent of the households in the United States have access to public transportation. The United States must expand public transportation to take full advantage of its environmental and economic benefits."

Below are just a few green activities at public transportation systems that improve the environment:

• Atlanta - The Metropolitan Atlanta Rapid Transit Authority recently started to install a new federally funded solar canopy at a bus garage. This will be the largest solar canopy installation in Georgia and the second largest in the country and will significantly off-set power usage at this facility.

• Lafayette, Ind. - CityBus broke ground on a wind turbine project on April 21. The $2.18 million project will power CityBus facilities with renewable wind energy and reduce dependence on fossil fuels.

• Minneapolis- Metro Transit runs its Hiawatha light rail line on a 20 percent blend of renewable sources such as hydropower, wind and biomass.

• Olympia, Wash. - Intercity Transit continues enhancement of its bus stops with installation of solar lights in bus shelters. Additionally, The Federal Transit Administration selected Intercity Transit to participate in a two-year training and assistance program to implement Environmental Sustainability Management Systems.

As of 2010, hybrid buses, natural gas buses and biodiesel-fueled vehicles were common among public transit systems and made up nearly 34 percent of all transit buses. Below are examples of the diversity of bus fleets across the country in small, mid-sized, and large systems, including some Earth Day bus events and announcements regarding new buses:

• Dallas - The Dallas Area Rapid Transit has recently finalized the purchase of up to 452 new natural gas-fueled buses.

• Eugene, Ore. - Lane Transit anticipates that later in the year, 50 percent of its bus fleet will be hybrid buses, thanks to the addition of 24 new hybrid buses.

• Seattle- King County Department of Transportation will take delivery of 93 hybrid-powered 40' coaches and an additional 86 articulated hybrid buses this year. By the end of 2011, Metro will have 541 hybrid-diesel electric buses, comprising 41 percent of Metro's fleet. Metro's current hybrid buses are demonstrating a 30 percent reduction in greenhouse gas emissions compared to the conventional diesel fleet.