Attached is the Western Division Employee Timetable #28 dated May 24, 1914. Thanks to Pat Hiatte (friscoot) for sharing.
First, Second and Third Class trains. First Class is superior (has highest priority) to Second and Third Class, and Second Class has higher priority than Third Class. Extras are the lowest priority in movement. First Class is almost always passenger trains and the hottest, expedited freight (such as perishables). Second Class (regular scheduled freight trains) - lesser than First, but greater than Third. The other factor affecting train movement is direction, generally a north-bound or east-bound train has right over a train of the same class traveling in the south-bound or west-bound direction. Extras fill in the gaps in between all the classed trains with priority determined by train order and timetable.