BC Transit – Air Brake Course

Crossed Lines (service and supply)
Two things can happen if the supply and service lines are crossed.
1. Trailer reservoir with no air: The law requires that a trailer reservoir hold its air for
15 minutes only. After that, the reservoir may be considered to be empty, leaving the
trailer with no brakes. No air, no brakes.
2. Trailer reservoir with air: The trailer has been parked for only a short time (less than
15 minutes) and there is air remaining in the reservoir.
The following slides will depict both scenarios. Whatever the case, performing a check
for proper trailer brake function before going into service is imperative.
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