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Properly attach air lines, electrical
line and other associated hoses (if
applicable).
Charge air system and if equipped
with a “no-slack ram”, do a tug test to
ensure the ram is energized.
Perform a visual inspection to ensure all
locking mechanisms are properly secured.
Place landing leg (if applicable) in
transport position and remove choc
Ensure hitching devices are secure and
re-check safety latch.


The most important task in the coupling
procedure is to physically and visually
check all connections. Failure to do so
may be the cause of a serious incident.

Coupling
mechanisms

Double trailer
combination types

When adding a second trailer to the rear
of a lead trailer, a converter mechanism is
needed. Each converter must have its own
fifth wheel attachment. There are three
different types of converters.

A TRAIN
This converter has an A shaped drawbar
that joins into a single pintle hitch point on
the lead trailer. Due to its A shape, it is often
called an A-dolly. When two trailers are
joined together using the A-dolly, the whole
unit is called an A train. These converters
provide two points of articulation (joints that
allow side to side or lateral movement). One
of these points is at the pintle and the other
is at the fifth wheel.


A train - example of a unit connected by
a type A converter dolly.

B TRAIN
In a B train, the converter is part of the
lead trailer. The fifth wheel assembly sits on
the rear axle of the lead trailer. It is either
permanently fixed in position or slides out
with the rear axle.

No converter dolly is required, as the
second unit connects directly to the
extended frame of the lead unit.


B train - example of a unit connected
by a type B converter dolly.

C TRAIN
A C train is like the A train, in that it uses
an independent converter. The difference
between the two is that the C train has
two drawbars and two pintle hitches in the
double drawbar converter.

CHAPTER FOUR OPERATING CLASS 1 VEHICLES 45

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