Any worthy compliance software is going to have to link all items (power unit-driver-trailer) in one fashion or another to make it worth while.
If not a driver / truck could be dispatched with one part or the other out of compliance which is of course what you are trying to get under control.
Some software is developed with safety as an afterthought, so be very sure of what you are looking at.
In this case, are accidents, violations which need to be tracked, treated as "separate" items thus upping the cost?
edit to add
Just do your homework on any software you are looking at and ask any and all questions until you get a suitable answer.