Mass transit riders in the region can leave their CharmPass tickets in their pockets on Tuesday.

For the second Earth Day in a row, rides on any Mass Transit Administration (MTA) bus, commuter bus, Mobility paratransit, light rail, Metro SubwayLink or MARC train will be free.

The MTA is joining other transit agencies around the country in similar promotions to encourage use of public transit as a way for individuals to reduce their carbon footprint.

“Earth Day is a timely reminder of the urgent need to protect our planet for future generations, and public transit plays a pivotal role in that effort,” Holly Arnold, administrator of the Maryland Transit Administration, said in a press release. “We hope offering free transit on Earth Day inspires more people to choose transit as a sustainable alternative to driving alone.”

The transportation sector is the leading source of greenhouse gas pollution in Maryland, driven largely by tailpipe emissions from personal cars and trucks.

Phasing out internal combustion engines (gas-powered) for electric vehicles is the most critical change needed to reduce transportation emissions, according to the United Nations Framework Convention on Climate Change. But converting car trips into rides on public transit — or into active trips like biking and walking — is also critical, experts agree.

Starting Tuesday, MTA riders can also catch the Earth Day bus, which will have its exterior frame decked out with art from six young people from Maryland.