at a road intersection, it is necessary for the towing
vehicle to continue forward to approximately the cen-
ter of the crossroad and then to cut sharply to the
right to allow for the shorter turning radius of the
semitrailer. The unit should be kept close enough to
the road edge when such a turn is made to eliminate
the possibility of a following vehicle attempting to pass
on the right.
(3) B a c k i n g . When backing the semitrailer with the tow-
ing vehicle, the towing vehicle is steered in the direc-
the semitrailer is to be backed to the right, the steer-
ing wheel of the towing vehicle is turned to the left,
or counterclockwise. The front of the semitrailer will
be pushed to the left and the semitrailer wheels will
be steered to the right.
(4) Stopping. In normal operation, the brakes of the tow-
ing vehicle and those of the semitrailer are applied
Brake pressure should be applied
gradually and smoothly.
Note. On steep grades and slippery surfaces, the hand valve on
the towing vehicle must be applied first; then, the brakes of the
towing vehicle are applied. This will tend to reduce the possibility
of the trailer jackknifing or swinging out of the line of travel. Semi-
trailer brakes must not be used alone for braking.
(5) P a r k i n g .
combination is to be parked, do not set the air brakes
and depend upon them to hold the vehicles. Place the
chock blocks before or behind two wheels, as required,
to prevent the wheels from rolling, if the unit is to
be left unattended.
Uncoupling Semitrailer From Towing Vehicle.
(1) B l o c k w h e e l s . D e p e n d i n g u p o n t h e t e r r a i n , p l a c e c h o c k
on each side of the semitrailer.
valves on the service and emergency air lines at the
vehicular hose from the service and emergency air hose
couplings (fig. 28) on the nose of the semitrailer, The
automatically when the
Fit dummy coup-
emergency air hose is uncoupled.
lings on semitrailer air hose couplings.