The “Genesis” is a passenger locomotive that was developed for Amtrak. In contrast to the usual road switchers, they have a self-supporting and streamlined locomotive body. The P40DC initially built produces 4,000 hp and has a top speed of 103 mph. In the later P42DC, these figures were increased to 4,250 hp and 110 mph. Amtrak received 44 of the first variant and 207 of the second. 21 others are operated by Canada's Via Rail.

The power comes from the proven 7FDL with 16 cylinders. The alternator for the head-end power depends on the engine speed to deliver the required 60 Hertz. Since the prime mover has to run at a speed of 900 rpm when the alternator is switched on, the P42DC, for example, then only has a gross output of 3,850 hp. Depending on the length of the train, only 2,525 hp may then be available for traction.

The Genesis quickly became Amtrak's standard locomotive for all longer, non-electrified lines. 15 P40DC were rebuilt to the same level as the P42DC. Heavy trains are usually pulled by two locomotives together, with only one locomotive being responsible for delivering head-end power to the train. The Amtrak locomotives have now reached the end of their long-distance service careers and are being replaced with Siemens Chargers. Some have long been sold to various companies who use them in commuter traffic.