As part of a settlement with the Environmental Protection Agency regarding clean-air regulations, Wal-Mart will be outfitting its entire fleet of 6,500 trucks with idle-reducing generators.

The settlement is part of a lawsuit by the states of Connecticut and Massachusetts regarding trucks idling outside of Wal-Mart stores. According to an EPA release, inspectors documented trucks parked outside of stores in both states – both of which have anti-idling regulations for large trucks – during the daytime and overnight.

As its penalty, Wal-Mart was required to pay a fine of $50,000 and agreed to post signs nationwide at store loading docks warning drivers to shut off their engines when parked.

Wal-Mart will also begin adding generators to every truck in its fleet to help reduce the need for diesel engine idling, the Boston Globe reported. Currently, 600 trucks in New England are being installed with the alternative power sources, with a nationwide installation is expected to take several years.

“It’s good for the environment, and ultimately it will pay for itself,” Wal-Mart Spokesperson Marty Heirs told the Globe.