A watchman, Ernest Smith, at the Central Avenue railroad crossing in Canonsburg, PA, reported that 115 trains (passenger, coal, and general-freight), had crossed on a Thursday in April, 1902 on the Chartiers branch. That is a lot of traffic for a "simple" branch line! The pages linked to below provide all the prototype information about the equipment that has been verified to have run on the Chartiers branch, or that could have been seen on the branch, during the year 1924, my chosen era to model.
The Pennsy Power book states that the PRR had 7,556 steam locomotives in service in 1924. The most popular ones were: 2-8-0 (3335), 4-6-2 (700), 2-10-0 (598), and 2-8-2 (579).