@PH1975 posted:...what I've always found fascinating/intriguing is seeing different RR's ENGINES in multiple unit consists travelling across the country together. It's only been in the past few years that I've learned there's an understanding among all railroads that engine use is tracked and a comparable amount of use on the 'other' rr is provided as payback in due course.
It's called "Horsepower Hours." If you have a 3,000 HP locomotive and you use it for an hour, you've racked up 3,000 HP/HRS.
The railroads have found that it's much faster, efficient, and more cost effective to keep the motive power intact on a given train and run it through from origin to destination. That's why you may see locomotives from several different roads, all on the same train. The power inevitably gets all mixed around as motive power consists are changed.
Horsepower hours are tracked on a daily basis. They are typically paid back via more horsepower hours from home road power on other lines. There are whole departments at the railroads dedicated to the tracking and billing of Horsepower Hours.
