Increased use of dynamic braking, which involves the electric traction motors in locomotives, provides resistance to the rotating wheel axle.

Acela Express high speed trains and other new and remanufactured electric locomotives have enabled Amtrak to reduce energy consumption by up to eight percent through the use of a regenerative braking system. This braking system returns electric energy overhead to the catenary power system and replaces some of the electrical energy consumed.

The U.S. Department of Energy (DOE) has reported that Amtrak – on an energy-consumed-per-passenger-mile basis – is 18 percent more energy efficient than commercial airlines. Unlike commercial aviation, which mostly uses highly refined jet fuel, Amtrak uses diesel fuel produced at a higher volume per barrel of crude oil and electricity produced in the Northeast from a variety of fuels.

"AutoStop" on Amtrak?

Amtrak is installing a new automatic shut-off system in its diesel locomotive fleet to limit idling.

http://www.nationaltrainday.com/home