While DJ is right in 99% of the cases. There is a 1% exception potential. In some locations there will be multiple locomotives that are equally able to satisfy the needs for any job that is headquartered at that location. In that kind of situation, the local supervisor that will assign specific engines to specific crews for the local supervisors reasons. In my days of first level supervision at various yards in B&O's Baltimore Terminal each yard would start up to six crews each trick. The Yardmaster was responsible for assigning engines to specific crews. The decision would be governed by how much power or how light of a locomotive was necessary to accomplish the work purpose for each of the jobs. Yardmasters were also responsible for instructing crews where to tie down and secure their locomotives at the end of their tour of duty. Good yardmasters would get each of their crews performing productive job actions right out of the gate. Less than good yardmasters could tie themselves up in knots by assigning the wrong engines to crews and having those crew attempting the wrong work in concert with all the crews going to work. Power Bureau in concert with local terminal supervision and locomotive maintenance personnel will assign power to trains originating from that terminal and that power will normally continue to destination, with the exceptions being for the train to set off or pick up locomotives from outlying locations where the power is positioned for Local Freight/Road Switcher crews to originate and terminate. In many of the outlying locations there may be a 'daylight' and a 'night time' job that will share the power at the location Among the decision considerations that the Power Bureau juggle in making engine assignments are the fuel status vs. fueling during the trip, price of fuel at intermediate locations. Compliance with required 92 day mechanical inspections at specific major maintenance locations. Managing 'horsepower hour' accounts with connecting carriers for run through power amongst the carriers. Needless to say the working/defective condition of any particular engine.
