Just drove the Rogers Pass en route to and from the Kamloops Cowboy Festival and spotted some very long trains. One with three lead engines,two-could have been three but the guard rail cut the view-in the middle. When there's a couple hundred hoppers, five locos, gravity and friction the horsepower required to drag that gross weight up and down the mountains is obviously enormous. How do they decide how much HP is needed and where it's placed. Oh yeah, how come the cars aren't pulled straight, off the rails in those very sharp uphill curves? The strain on the inside rail of a curve must be x to the umteenth power.