"They sit on a spur of test track outside General Electric's locomotive factory in Erie, Pennsylvania, panting and grumbling like two old lions half asleep. The ominous, muttering rumble is the idle of 8,800 horsepower--24 cylinders with pistons big as buckets, turbochargers the size of washing machines, two V12 engines driving alternators five feet in diameter. For here are two units of the most advanced diesel-electric locomotives in the world:...