Union Pacific Railroad put into service one of the nation's first locomotives using environmentally friendly hybrid technology Tuesday, and the company called it an important step toward cutting air pollution generated by the ports of Los Angeles and Long Beach.

"It's a very efficient technology," said Michael E. Iden, the Union Pacific executive overseeing the company's conversion to a lower-emission fleet. The new breed of rail locomotive combines electric and diesel power and runs almost noiselessly.

"Typically, for about eight hours at a time, you won't even hear the engine running because it's using electricity from the batteries," Iden said.