I believe you can feed your 24 volt logic levels (or any higher DC voltage for that matter) directly into the arduino provided you use input resistors to limit input current to less than 1ma.
I would never trust that conditions remain "ideal" enough on a truck (or any similar industrial environment) to rely on just OHMS LAW to protect delicate input pins when the potential for error is so high and in this case the solution is screaming for "isolation" in the form of opto-couplers or solid state relays/standard relays.
my analogy again: I would so rather lose a finger than blow my brains out if something goes amiss.