A. An earlier incident
B. Held by the train dispatcher
C. Train traffic ahead of us
D. Police investigation
E. Unusual track condition
F. Broken rail
G. Signal problems
H. Mechanical problems
I. Collapsed building
J. Construction
K. Congestions ahead
L. Track work
M. Power outage
Note – these are all actual excuses for service delay/disruption/outage that I had personally experienced, some of them on a daily basis.