Pennsylvania engine service designation

Primary long distance engines- Passenger locomotives that run at speeds of up to 125 mph, and make limited stops between destinations
BR class 221 diesel units
EMD E units
T1 class 4-4-4-4s
EMD E7s
ALCO PA1s

Secondary long distance engines- Passenger locomotives that use same routes as long distance trains, but go slower and stop more often.

K series 4-6-2s

Dual service engines- Locomotives that are able to be used on both freight and passenger trains.
EMD F- units
EMD GP units
M series 4-8-2s
Q series 4-6-4-4s and 4-4-6-4s

Fast freight engines-Locomotives designated to haul fast freights like merchandise or the Tropicana juice train.
EMD SD units
L series 2-8-2s
I1s 2-10-0s
HC series 2-8-8-0s
HH series 2-8-8-2s

Slow freight engines- Locomotives designated to operate longer, heavier freight trains.
GE Dash 9s
GE Dash 8s
GE CWs
N series 2-10-2s
J1 series 2-10-4s

Branch line passenger trains- Locomotives designated to operate passenger trains on branch lines or locals.
EMD Budd cars

Branch line/ local steam engines- Locomotives designated to run local or branch line trains.
H series 2-8-0s
G series 4-6-0s
D series 4-4-0
E series 4-4-2s

Switchers- Locomotives designated to switch cars in RR yards.
A series 0-4-0s
B series 0-6-0s
C1 class 0-8-0s
tank engines
EMD SW locomotives