FM 90-13/FMFM 7-26
Appendix B
Cr o s s i n g Me a n s
GENERAL
bridge. The vehicle class number must not exceed the
Crossing means is the equipment used to carry a
published risk class for the bridge type being crossed.
force across a water obstacle. This equipment is spe-
After the crossing, and before other traffic is permitted,
cially designed to operate within certain limits, and
the engineer officer reinspects the entire bridge for any
commanders must understand these limits if the force
damage.
is to cross safely.
This appendix supplements a general description of
A safety matter that affects operational use is the
crossing means discussed in Chapter 4. It provides a
load capacity of rafts, bridges, and equipment. The
pictorial review as well as equipment capability tables
quantities shown on the Equipment Characteristics
useful in selecting crossing means and planning cross-
Chart, page B-3, are the normal capacities or the design
ing operations.
capabilities. In exceptional circumstances, certain
Available crossing means dictate both crossing
safety factors or margins allow increased loadings.
operations and the force buildup rate on the far shore.
These capacities have been deliberately omitted here
Since the available crossing means often limits his op-
because they are not intended for use in operational
tions, the commander must understand the transporta-
planning. The standard or design capabilities are
tion of forces across the water before developing his
provided for normal crossings. The exceptional
tactics.
category is intended for special situations using the
The military means to cross a river are 
terms caution or risk crossings.
" Fording vehicles.
In addition to the command decision required to
" Boats.
employ caution and risk crossing loads, commanders
" Aircraft.
must consider the physical status of the equipment.
" Amphibious vehicles.
Thus, crossing area or crossing force commanders ob-
" Rafts.
tain a professional judgement from the engineer. He
" Bridges.
weighs these factors with the tactical needs prior to
directing increased loading, keeping in mind that the
FORDING VEHICLES
equipment may be lost for future use.
Combat vehicles can ford shallow rivers that have
In a normal crossing, the vehicle class number is
limited stream velocity and stable beds. Some vehicles
equal to or less than the bridge classification number,
have kits to increase fording depth. Fording is possible
vehicles maintain 30-meter intervals on fixed or floating
for stream velocity less than 1.5 meters per second.
bridges, and speed is restricted to 15 mph. Sudden
Riverbeds at fording sites must be firm and free of large
stopping or acceleration is forbidden.
rocks and other obstructions. Vehicle operator
In a caution crossing, vehicles with a classification
manuals contain specific depth capabilities and re-
exceeding the capacity of the bridge by 25 percent are
quired adaptations.
allowed to cross under strict traffic control, The caution
class number of standard freed or floating bridges may
Boats
be obtained from FM 5-34, TC 5-210, or other ap-
Pneumatic assault boats are the primary crossing
propriate TMs. Caution crossings require the vehicle
means for dismounted infantry and accompanying ele-
to remain on the centerline and maintain a 50-meter
ments. For light infantry, assault boats may be the only
distance from other vehicles. They also require vehicles
means required if air resupply is available. They carry
not to exceed 13 kph (8 mph), not to stop, not to
12 assault troops and a two-man engineer crew in a
accelerate, and not to shift gears on the bridge.
silent or powered crossing.
A risk crossing may be made only on standard,
Aircraft
prefabricated freed and floating bridges. Risk crossings
Army aircraft are an alternative to assault boats for
are made only in the greatest emergencies. The vehicle
dismounted infantry. They give the force the capability
moves on the centerline and is the only vehicle on the
to concurrently seize objectives from the exit bank out
bridge. It does not exceed 5 kph (3 mph), does not stop,
to the bridgehead line. Helicopters also lift other
does not accelerate, and does not shift gears on the
Crossing Means B-1
FM 90-13/FMFM 7-26
crossing assets from rear areas to the river and carry bridges. They often assemble bridges from the rafts
essential combat support and critical resupply across
used earlier. Ribbon, M4T6, and Class 60 bridges are
the river.
currently available.
The ribbon bridge is the primary assault bridge be-
Amphibious Vehicles
cause it is quick to assemble. The M4T6 bridge replaces
Some combat vehicles can swim. Bank entry and exit
the ribbon bridge, which continues to move forward
points must be clear of obstructions and have slopes
with the advancing force. Because it is manpower-in-
consistent with vehicle capabilities. Current velocity
tensive, the M4T6 is slower to assemble than the ribbon
sets limits. Crews of amphibious vehicles prepare and
bridge. Preassembly of M4T6 floats in rear areas sig-
inspect each vehicle before entering the water. En-
nificantly reduces final assembly time on the river. The
gineer assistance, including recovery vehicles and
Class 60 bridge supplements M4T6 bridges. It is an old
standing cables, maximizes swimming opportunities.
system still available in some depots; however, it is
labor-intensive and requires an air compressor and a
Rafts
crane.
Heavy rafts are often the initial crossing means for
Fixed bridges rest on the river banks and inter-
tanks and other fighting vehicles. They are faster to
mediate supports instead of floating on the water. They
assemble than bridges and can operate from multiple
span ravines as well as rivers. They have limited use for
sites to reduce their vulnerability. The two types of
the initial assault, because they are slow to assemble
heavy rafts currently available are ribbon and M4T6.
and vulnerable to threat action. Where appropriate,
The LTR supplements heavy rafts for vehicles under
they supplement or replace float bridges. Engineers
MLC 16.
also use fixed bridges to repair existing damaged
Bridges
bridges. The M2 Bailey bridge and medium girder
Rafts alone cannot handle the total volume of traffic
bridge (MGB) are currently available. The AVLB can
in the needed time. Floating bridges are the primary
be used to cross short gaps.
means to rapidly cross the force and its supplies. The
same units that provide heavy rafts also provide float
B-2 Crossing Means