TM 5-5420-278-10
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BRIDGE OPERATION (Contd)
d. Ramp Bay Controls. Prior to allowing vehicle traffic on bridge, bridge OIC
checks the ramp cylinder controls. The ramp bay should be let down additionally
and pressed to the shore prior to vehicle crossing. Position both ramp cylinder pump
levers in the DOWN position, and pump each pump 12 times (25 times if using only
one pump. Then place the ramp cylinder pump levers in the TRANSPORT/
CROSSING position. This condition will allow the ramp bay to automatically adjust
to any rise in water level. To compensate for falling water level, the pump lever
must be placed in the UP position and raised to the desired height until the ramp
bay obtains the lower water level. When the ramp bay obtains the proper water
level, place the lever in the TRANSPORT/CROSSING position before allowing
traffic on bridge. The maximum angle the ramp bay can rise is 20 degrees. Some
vehicles, such as Armored Vehicle Launched Bridge (AVLB), must be guided onto
the bridge because of the interference of vehicle equipment with bridge deck.
CAUTION
Before a bridge crossing is performed, the operator must
ensure all sharp-edged stones are removed from tire treads,
tracks, and roadway surface. Failure to comply may cause
dents or puncture holes in roadway.
Stopping, accelerating, turning, and shifting of gears on the
bridge is not permitted during Caution or Risk crossing, and
should be kept at a minimum during Normal crossings.
Failure to comply may result in damage to equipment.
Bridge commander must observe leading edge of bridge and
decrease crossing rating (Normal to Caution to Risk) or halt
operations, as necessary, if continuous water is coming over
bow dam.
e. Traffic. Prior to allowing vehicle traffic on bridge, open longitudinal upper
couplings on interior bays only. Note GVW of each vehicle. The capacities of the IRB
at various stream velocities are found in table 7. Vehicles may travel anywhere
within the yellow lines on the roadway in normal crossings at reasonable speeds.
Adjust position of ramp plates as necessary. In Caution crossings, all vehicles are
restricted to the center of the bridge and to speeds up to 8 mph (12.87 kph). A 150-ft
(45.72-m) tail-to-head spacing is required for Caution crossings, while a 100-ft
(30.48-m) spacing is required for Normal crossings. Risk crossings require the
following: the vehicle must be on the roadway centerline, it must travel at less than
3 mph (4.83 kph), and only one vehicle is permitted on the bridge at a time.
(1) DISTANCE BETWEEN VEHICLES:
For standard load, 98 ft (30 m); for exceptional load, 164 ft (50 m).
(2) MAXIMUM CROSSING SPEEDS:
Under standard load up to
MLC 40
12.4 mph (20 km/h)
Under standard load up to
MLC 40
6.2 mph (10 km/h)
Under exceptional load
MLC 70
3.1 mph (5 km/h)
