When uncoupling the rear trailer of a triples combination, the first step is to:
a.Disconnect the air and electrical lines from the middle trailer to the converter dolly
b.Release the dolly fifth wheel latch
c.Park the combination on level ground and set all brakes
d.Remove the safety chains first
Explanation
The first step when uncoupling any trailer combination is to park on level ground and set all parking brakes on every unit. This ensures nothing moves during the uncoupling process and prevents accidents.