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Chapter 5

Route Classification (Continued)

FERRY RECON

Ferries are considered obstructions to traffic flow and are indicated by the abbreviation "OB" in the route-classification formula. Ferryboat construction varies widely and ranges from expedient rafts to ocean-going vessels. Ferries differ in physical appearance and capacity depending upon the water's width, depth, and current and the characteristics of the traffic to be moved. Ferries may be propelled by oars; cable and pulleys; poles; the stream current; or steam, gasoline, or diesel engines.

CIVIL FERRIES AND FERRY SITES

Usually, the capacity of a civil ferryboat is expressed in tons and total number of passengers. In addition, it is often assigned an MLC number. Ensure that you record the capacity of each ferry when more than one is used at a given site. The ferries may vary in capacity.

Ferry slips (or piers) are usually provided on each shore to permit easy loading of passengers, cargo, and vehicles. The slips may range from simple log piers to elaborate terminal buildings. A distinguishing characteristic of a ferry slip is often the floating pier that adjusts, with changes in the water depth, to the height of the ferryboat.

Approach routes to ferry installations have an important bearing on using the ferry. Reconning and recording the conditions of the approaches (including the load-carrying capacity of landing facilities) is very important.

Limiting characteristics of ferry sites that should be considered are the--

  • Width of the water barrier from bank to bank.
  • Distance and time required for the ferryboat to travel from one bank to the other.
  • Depth of the water at each ferry slip.
  • Ease in which each landing site can be defended.

Climatic conditions affect ferry operations. Fog and ice substantially reduce the total traffic-moving capacity and increase the hazard of the water route. Therefore, you must consider data on tide fluctuations, freezing periods, floods, excessive dry spells, and their effects on ferry operations.

FERRY INFORMATION

Record limited ferry information (such as the following) on maps or overlays by using the symbol shown in Figure 5-29. Figure 5-30 gives examples of completed ferry symbols.

Figure 5-29. Ferry symbol

Figure 5-30. Sample ferry symbols

  • The geographic location of the ferry is shown by an arrow from the symbol to the location of the ferry on a map or overlay. The symbol may be drawn on the map or overlay on either side of the stream.
  • A serial number is assigned to each ferry, for later reference. Numbers must not be duplicated within any one map sheet, overlay, or document. Some maps will already show a ferry serial number. Use this number for your recon. If you do not find a number, record a number according to the unit's SOP.
  • The type of ferry (V for vehicular and P for pedestrian) is shown after the serial number. If the ferry can haul vehicles, it can also haul pedestrians.
  • The deck's MLC is placed in the bottom left box of the symbol. Most ferries have this information on their data plate.
  • The dead-weight capacity of the ferry is the MLC plus the actual weight of the ferry, in short tons.
  • The turnaround time is shown by the number of minutes required to cross the water obstacle, unload, and return.

When drawing the approach-condition portion of the symbol, pay attention to the direction of stream flow. Left and right banks are determined by looking downstream. Approach conditions are determined in the same manner as for fords. A difficult approach is shown by irregular lines placed on the corresponding side of the basic symbol.

A question mark is substituted for unknown or undetermined information. Detailed ferry recon information is recorded on DA Form 1252 (see Figures 5-31 and 5-32).

Figure 5-31. Sample Ferry Reconnaissance Report (front)

Figure 5-32. Sample Ferry Reconnaissance Report (back)

MILITARY FERRY AND RAFTING

Recon personnel will be required to locate and report suitable sites for military rafting or ferrying operations. Military floating bridges are presently available for such operations. esirable site characteristics are--

  • Current velocity between 0 and 1.6 meters per second.
  • Banks that permit loading without a great deal of preparation.
  • Approaches that permit easy access and egress.
  • Strong, natural holdfasts.
  • Sites with no shoals, sandbars, or snags.
  • Sites clear of obstacles immediately downstream.
  • Sites clear of mines and booby traps.
  • Sites with enough depth to prevent grounding the raft or ferry during loading and unloading operations or when crossing.
  • Suitable raft-construction sites (dependent on type of raft).
  • Holding areas for vehicles awaiting passage.
  • A suitable road network to support crossing traffic.

NOTE: Refer to FM 90-13 for rafting operations.

ROAD RECON PROCEDURE

Perform a technical road recon to determine the traffic capabilities of a road within a route. In general, a road consists of a road surface, base course, and subgrade (see Figure 5-33).

Figure 5-33. Parts of a road

BASE COURSE AND SUBGRADE

The base course and subgrade are the intermediate fill. They are usually composed of gravel or crushed rock. Soils may form the subgrade. See Tables 5-3 and 5-4.

Table 5-3. Soil characteristics of roads and airfields

Major Divisions

Letter

Name

Field
CBR

Coarse-
grained
soils
Gravel
and
gravelly
soils

GW

Well-graded gravels or gravel-sand mixtures,
little or no fines

60-80

GP

Poorly graded gravels or gravel-sand mixtures,
little or no fines

25-60

GM

d1

Silty gravels, gravel-sand-silt mixtures

40-80

u2

20-40

GC

Clayey gravels, gravel-sand-clay mixtures

20-40

Sand and
sandy
soils

SW

Well-graded sands or gravelly sands, little or no
fines

20-40

SP

Poorly graded sands or gravelly sands, little or
no fines

10-25

SM

d1

Silty sands, sand-silt mixtures

20-40

u2

10-20

SC

Clayey sands, sand-clay mixtures

10-20

Fine-
grained
soils
Silts and
clays
(liquid
limits >50)

ML

Inorganic silts and very fine sands, rock flour,
silty or clayey fine sands, or clayey silts with
slight plasticity

5-15

CL

Inorganic clays of low to medium plasticity,
gravelly clays, sandy clays, silty clays, lean clays

5-15

OL

Organic silts and organic silt-clays of low
plasticity

4-8

Silts and
clays
(liquid
limits >50)

MH

Inorganic silts, micaceous or diatomaceous fine
sandy or silty soils, elastic silts

4-8

CH

Inorganic clays of high plasticity, fat clays

3-5

OH

Organic clays of medium to high plasticity,
organic silts

3-5

Highly organic soils

Pt

Peat and other highly organic soils  
1Indicates liquid limit is 28 or less, and plasticity index is 6 or less.
2Indicates liquid limit is 28 or greater.

Table 5-3. Soil characteristics of roads and airfields (continued)

Letter

Value as Foundation
When Not Subject to
Frost Action3

Value as Base
Directly Under
Bituminous Pave-
ment

Potential
Frost
Action4

Compressibility
and
Expansion

Drainage
Characteristics

GW

Excellent Good None to
very
slight

Almost none

Excellent

GP

Good to excellent Poor to fair None to
very
slight
Almost none Excellent

GM

d1

Good to excellent Fair to good Slight to
medium
Very slight Fair to poor

u2

Good Poor Slight to
medium
Slight Poor to
practically
impervious

GC

Good Poor Slight to
medium
Slight Poor to
practically
impervious

SW

Good Poor None to
very
slight
Almost none Excellent

SP

Fair to good Poor to not suitable None to
very
slight
Almost none Excellent

SM

d1

Good Poor Slight to
high
Very slight Fair to poor

u2

Fair to good Not suitable Slight to
high
Slight to medium Poor to
practically
impervious

SC

Fair to good Not suitable Slight to
high
Slight to medium Poor to
practically
impervious

ML

Fair to poor Not suitable Medium
to very
high
Slight to medium Fair to poor

CL

Fair to poor Not suitable Medium
to high
Medium Practically
impervious

OL

Poor Not suitable Medium
to high
Medium to high Poor

MH

Poor Not suitable Medium
to high
High Fair to poor

CH

Poor to very poor Not suitable Medium High Practically
impervious
OH Poor to very poor Not suitable Medium High Practically
impervious
Pt Not suitable Not suitable Slight Very high Fair to poor
3Values are for subgrades and base courses except for base courses under bituminous pavement.
4Indicates whether these soils are susceptible to frost.

Table 5-4. Principal soil types

Name

Description

Gravel A mass of detached rock particles, generally waterworn, which passes a 3-inch sieve and is retained on a No. 4 sieve (0.187 inches).
Sand Granular material composed of rock particles which pass a No. 4 sieve (0.187 inches) and are retained on a No. 200 sieve (0.0029 inches). It is difficult to distinguish sand from silt when the particles are uniformly small. Dried sand, however, differs from silt in that it has no cohesion and feels grittier.
Silt A fine, granular material composed of particles which pass the No. 200 sieve (0.0029 inches). It lacks plasticity and has little dry strength. To identify, prepare a pat of wet soil and shake it horizontally in the palm of the hand. With typical inorganic silt, the shaking action causes water to come to the surface of the sample, making it appear glossy and soft. Repeat tests with varying moisture contents. Squeezing the sample between the fingers causes the water to disappear from the surface and the sample quickly stiffens and finally cracks or crumbles. Allow sample to dry, test its cohesion, and feel by crumbling with the fingers. Typical silt shows little or no dry strength and feels only slightly gritty in contrast to the rough grittiness of fine sand.
Clay Extremely fine-grained material composed of particles which pass the No. 200 sieve (0.0029 inches). To identify, work a sample with the fingers, adding water when stiffness requires. Moist sample is plastic enough to be kneaded like dough. Test further by rolling ball of kneaded soil between palm of hand and a flat surface. Clay can be rolled to a slender thread, about 1/4 inch in diameter, without crumbling; silt crumbles, without forming a thread. Measure hardness of dry clay by finger pressure required to break a sample. It requires much greater force to break dry clay than dry silt. Clay feels smooth in contrast to the slight grittiness of silt.
Organic Soil composed of decayed or decaying vegetation, sometimes mixed with fine-grained mineral sediments such as peat or muskeg. It is identified by coarse and fibrous appearance and odor. Odor may be intensified by heating. Plastic soils containing organic material can be rolled into soft, spongy threads.

ROAD-CAPACITY COMPUTATIONS

The charts that follow will help give you an accurate estimation of the load-bearing capacity of a road with flexible pavement. Tables 5-3, 5-4, and 5-5 and Figure 5-34 will help determine the road's load-bearing capacity. The load-bearing capacity of a road for wheeled vehicles is made by measuring the thickness of the surface and base course and by determining the type of subgrade material.

Table 5-5. Maximum axle and wheel loads for wheeled vehicles

Hypothetical Vehicle
Class Number

Maximum Single-Axle
Load (in tons)

Maximum Single-Wheel
Load (in pounds x 1,000)

4

2.5

2.5

8

5.5

5.5

12

8.0

8.0

16

10.0

10.0

20

11.0

11.0

24

12.0

12.0

30

13.5

13.5

40

17.0

17.0

50

20.0

20.0

60

23.0

20.0

70

25.5

20.0

80

28.0

20.0

90

30.0

20.0

100

32.0

20.0

120

36.0

20.0

150

42.0

21.0

Figure 5-34. Load-bearing capacity of roads with a flexible surface

ROAD-CLASSIFICATION FORMULA

The road-classification formula is a systematic way of describing the worst section of a road. Do not confuse it with the route-classification formula. Recorded information from the road-classification formula is included in the route-classification formula. The following paragraphs describe each portion of the formula shown below:

B g s

4 / 5

r

(8 km)

(OB)

(T)

(1)

(2)

(3)

(4)

(5)

(6)

(1) Limiting characteristics. Prefix the formula with "A" if there are no limiting characteristics and "B" if there are one or more limiting characteristics. Represent an unknown or undetermined characteristic by a question mark, together with the feature to which it refers. In the example above, the letter g indicates steep gradients and the letter s indicates a rough surface (see Table 5-6).

Table 5-6. Symbols for limiting characteristics

Limiting
Characteristics

Criteria

Symbol

Sharp curves

Sharp curves with radius of 25 meters and less (82 ft); are
also reported as obstructions

c

Steep gradients

Steep gradients, 7 percent or steeper; such gradients are
also reported as obstructions

g

Poor drainage

Inadequate ditches, crown or camber, or culverts; culverts
and ditches blocked or otherwise in poor condition

d

Weak
foundation

Unstable, loose, or easily displaced material

f

Rough surface

Bumpy, rutted, or potholed to an extent likely to reduce
convoy speeds

s

Excessive
camber or
superelevation

Falling away so sharply as to cause heavy vehicles to skid or
drag toward shoulders

j

(2) Minimum traveled-way width. Express this width in meters followed by a slash and the combined width of the traveled way and the shoulders. In the example above, the minimum traveled way is 4 meters and the combined width is 5 meters.

(3) Road-surface material. Express this with a letter symbol. The formula above describes the surface material as r, meaning water-bound macadam. Use the symbols listed in Table 5-7; they are further related to the X, Y, and Z route types of the route classification described earlier in route-recon procedures.

Table 5-7. Symbols for type of surface materials

Symbol

Material

Route Type

k

Concrete Type X; generally heavy duty

kb

Bituminous (asphaltic) concrete (bituminous plant
mix)
Type X; generally heavy duty

p

Paving brick or stone Type X or Y; generally heavy
duty

pb

Bituminous surface on paving brick or stone Type X or Y; generally heavy
duty

rb

Bitumen-penetrated macadam, water-bound
macadam with superficial asphalt or tar cover
Type X or Y; generally medium
duty

r

Water-bound macadam, crushed rock or coral or
stabilized gravel
Type Y; generally light duty

l

Gravel or lightly metaled surface Type Y; generally light duty

nb

Bituminous surface treatment on natural earth,
stabilized soil, sand-clay, or other select material
Type Y or Z; generally light duty

b

Used when type of bituminous construction cannot
be determined
Type Y or Z; generally light duty

n

Natural earth stabilized soil, sand-clay, shell,
cinders, disintegrated granite, or other select
material
Type Z; generally light duty

v

Various other types not mentioned above Classify X, Y, or Z depending on
the type of material used
(indicate length when this symbol
is used).

(4) Road length. Express the road length in kilometers and place in parentheses.

(5) Obstructions. Indicate any obstructions along a road by placing the symbol "OB" after the road length, as shown in the example above. Details of the obstructions are not shown in the formula; they are reported separately by appropriate symbols on accompanying maps or overlays or on DA Form 1248. Report the following obstructions:

  • Overhead obstructions (less than 4.3 meters over the route).
  • Constrictions in traveled-way widths less than 6 meters for single-flow traffic or less than 8 meters for double-flow traffic (tracked or combination vehicles [see Table 5-1]).
  • Slopes of 7 percent or greater.
  • Curves with a radius of less than 25 meters (report curves of 25.1 to 45 meters).

(6) Blockage. If blockage is regular, recurrent, and serious, then the effects of snow blockage and flooding are indicated in the road-classification formula. The symbol for snow blockage is "T" and the symbol for frequent flooding is "W."

EXAMPLES OF THE ROAD-CLASSIFICATION FORMULA

A sample Road Reconnaissance Report is shown in Figures 5-35 and 5-36. The following are examples of the road-classification formula:

Figure 5-35. Sample Road Reconnaissance Report (front)

Figure 5-36. Sample Road Reconnaissance Report (back)

  • A 5.0/6.2k--road with no limiting characteristics or obstructions, a minimum traveled way of 5.0 meters, a combined width of traveled way and shoulders of 6.2 meters, and a concrete surface.
  • B g s 4/5 1 (OB)--road with limiting characteristics of steep gradients and a rough surface, a minimum traveled way of 4 meters, a combined width of 5 meters, gravel or lightly metaled surfaces, and obstructions.
  • B c (f?) 3.2/4.8 p (4.3km) (OB) (T)--road with limiting characteristics of sharp curves and unknown foundation, a minimum traveled way of 3.2 meters, a combined width of 4.8 meters, paving brick or stone surface, obstructions and that is 4.3 kilometers longsubject to snow blockage.

NOTES:

1. Where rock slides are a hazard or poor drainage is a problem, include information on a written enclosure or legend.

2. DA Form 1248 is primarily self-explanatory. However, ensure that a new classification formula is entered each time the road changes significantly, as depicted in Figure 5-36.

BRIDGE-CLASSIFICATION RECON

A bridge recon must take place to ensure that commanders know what bridge load-carrying capabilities are along a certain route or what material is needed to destroy a bridge. Engineers are responsible for reconning all bridges.

REQUIRED BRIDGE INFORMATION FOR CLASSIFICATION PROCEDURES

This manual reviews the basics of hasty bridge load-classification procedures and recon procedures for bridge destruction. Appendix B references hasty bridge classification. (Refer to FM 5-446 for a complete discussion of bridge-classification procedures.) The Sheffield Method for bridge destruction is discussed in FM 5-250.

The method of bridge load classification covered in Appendix B is adequate for most bridge recons. It allows vehicle operators to avoid bridge failure by determining what can cross the bridge without causing damage. Vehicle operators may cross without restrictions if their vehicle's load class (including the load) is less than or equal to the bridge's load class. The vehicle's load class can be found in the vehicle's TM.

Appendix B covers the most common bridges in existence today, including a--

  • Timber or steel trestle bridge with timber deck.
  • Steel-stringer bridge with concrete deck.
  • Concrete steel-stringer bridge.
  • Concrete T-beam bridge with asphalt surface.
  • Masonry arch bridge.

REQUIRED INFORMATION

To classify a bridge (see Appendix B), you must know the information concerning the bridge's basic components, including the following:

  • Approaches (the portions of a route leading to a bridge). Approaches may be mined or booby trapped, requiring thorough investigation during a recon.
  • Substructure (lower part of a bridge). The substructure consists of the abutments and intermediate supports that transfer the bridge's load to the ground. It is important to measure all aspects of an abutment, including its height, width, and length; the abutment wings; and the intermediate supports for bridge demolition missions. It may be more feasible to destroy the intermediate supports or abutments when compared to the rest of the bridge structure.
  • Superstructure (the upper part of a bridge). The superstructure consists of the following components (see Figure 5-37):
-- Stringers rest on and span the distance between the intermediate supports or abutments. Stringers are the superstructure's main load-carrying members. They receive the load from the flooring and the vehicles and transfer it to the substructure.
-- The flooring system often consists of both decking and tread. The decking is laid directly over the stringers at right angles to the centerline of the bridge. The tread is laid parallel to the centerline of the bridge and between the curbs.
-- Curbs are placed at both edges of the flooring to guide the vehicles. A vehicle with an axle that is wider than the traveled-way width (between the curbs) cannot cross the bridge. Most bridges, however, allow for vehicular overhang beyond the normal traveled area. This allowance is called horizontal clearance above the curbs and is a safety factor. Commanders must perform a risk analysis before attempting such a crossing.
-- Railings along the bridge are built to guide drivers and to protect vehicular and foot traffic.
-- Trusses are used in some bridge superstructures, either above or below the traveled way, to increase the load-carrying capacity. A truss is a structural element made of several members joined together to form a series of triangles.
-- The number of members in each span is noted where applicable (for example, stringer bridges and concrete T-beam bridges). Exact dimensions of specific bridge members are taken as outlined later in this chapter.
-- The span length is measured from center to center of the supports. The bridge's classification is usually based on the weakest span. If the weakest span is apparent, no other spans need to be reconned. However, if the weakest span is difficult or impossible to locate, all spans must be classified. Even if several spans look identical, actual measurements should be taken to prevent error.
-- The traveled-way width is measured between the inside faces of the curbs. However, the horizontal clearance on a truss bridge is measured from a point 1.21 meters above the roadway.

Figure 5-37. Bridge parts

BRIDGE CONDITION

It is essential to note the bridge's general condition, paying particular attention to evidence of damage from natural causes (rot, rust, and deterioration) or combat action. Classification procedures presume that a bridge is in good condition. If the bridge is in poor condition, the class obtained from mathematical computations must be reduced according to the classifier's judgment.

WIDTH AND HEIGHT RESTRICTIONS

Table 5-8 lists width restrictions for bridges. If a one-lane bridge does not meet width requirements, post a rectangular warning sign under the classification sign showing the actual clear width (see Figure 5-38). If this is a route restriction, annotate it in the route-classification formula. For a two-lane bridge, downgrade the two-way classification to the highest class for which it does qualify (one-way class is not affected). Post a limited-clearance sign if the overhead clearance is less than 4.3 meters. These signs must be a minimum of 40 centimeters in height or width, with a yellow background, and the appropriate description in black letters. Separate rectangular signs are used if necessary to denote width limitations, height limitations, or other technical information. The same signs are used for tunnels, if applicable.

Table 5-8. Minimum roadway widths

Roadway Width
(meters)

Bridge Classification

One-Way

Two-Way

2.75 to 3.34

12

0

3.35 to 3.99

30

0

4 to 4.49

60

0

4.5 to 4.99

100

0

5 to 5.4

150

0

5.5 to 7.2

150

30

7.3 to 8.1

150

60

8.2 to 9.7

150

100

Over 9.8

150

150

NOTE: Minimum overhead clearance
for all classes is 4.3 meters

Figure 5-38. Width and height signs

BRIDGE TRAFFIC-CONTROL PROCEDURE

Posting standard bridge signs and other signs needed for proper and efficient traffic control across a bridge is an engineer's responsibility. Additional signs are used when it is necessary to warn vehicles that require special controls while crossing. When necessary, holding areas, turnouts for parking and unloading vehicles, and checkpoints are installed near bridges to provide the necessary control during crossings.

FULL NORTH ATLANTIC TREATY ORGANIZATION (NATO) BRIDGE SYMBOL

Bridge information is recorded on a map or overlay by using the full NATO bridge symbol (see Figure 5-39). It is different from an on-site bridge-classification sign; do not confuse the two. The information necessary for the full bridge symbol includes the--

  • Bridge's serial number.
  • Geographic location.
  • Bridge's MLC.
  • Overall length.
  • Traveled-way width.
  • Overhead clearance.
  • Available bypasses.

Figure 5-39. Full NATO bridge symbol

A bridge serial number is assigned for future reference and is recorded in the symbol's lower portion (assign a number according to the unit's SOP). For proper identification, do not duplicate serial numbers within any one map sheet, overlay, or document. The unit's S2 can obtain special maps containing bridge information for developed areas of the world.

The bridge's geographic location is shown by an arrow extending from the symbol to the exact map location. The bridge's MLC number is shown in the symbol's top portion. This number indicates the bridge's carrying capacity; classifications for both single- and double-flow traffic are included. In those instances where dual classifications for wheeled and tracked vehicles exist, both classifications are shown.

The bridge's overall length is the distance between abutments, measured along the bridge's centerline. This figure is placed to the right of the circle and is expressed in meters.

The minimum lane width is the clear distance between curbs. Place this figure below the symbol and express it in meters. Bridges may be obstructions to traffic flow because the traveled-way width of the overall route may be reduced on the bridge to below the minimum standards prescribed in Table 5-1.

The overhead clearance is the minimum distance between the bridge's surface and any obstruction above it. This figure is shown (in meters) to the left of the symbol. Underline any overhead clearance less than the minimum required by the bridge class number (see Table 5-9). Unlimited overhead clearance is indicated by the symbol . Often a telltale (see Figure 5-40) or other warning device is placed before the bridge to indicate overhead-clearance limitations. Report any overhead clearance less than 4.3 meters as an obstruction in the route-classification formula. A question mark is used to indicate information that is unknown or undetermined and is included as part of the bridge recon symbol. See Appendix E for signs used to mark roads and bridges.

Table 5-9. Minimum overhead clearance for bridges

Bridge
Classification

Minimum Overhead
Clearance

Up to 70 4.5 meters
Above 70 4.5 meters

Figure 5-40. Telltale

Railway bridges, which could be used by road vehicles in an emergency, are indicated as use easy or use difficult. Samples of the full NATO bridge symbol used to indicate a railway bridge can be found in the glossary.

NOTE: A railroad bridge is considered to be easy to adapt for use if it can be adapted in less than 4 hours with 35 soldiers and the appropriate resources.

THE BRIDGE RECONNAISSANCE REPORT

A systematic bridge recon obtains valuable data. However, this data will not benefit anyone unless it is recorded in an organized manner. Use DA Form 1249 to report information concerning any reconned bridge, as follows:

  • Column 1. Record the assigned serial number. This number matches the serial number used in the bridge symbol of the route-classification overlay.
  • Column 2. Record the grid coordinates, with the map identifier, of the actual bridge site.
  • Column 3. Record horizontal clearance information, in meters. Horizontal clearance is the clear distance between the inside edges of the bridge structure, measured at a height of 0.3 meter above the surface of the traveled way and upwards. However, horizontal clearance for truss bridges is measured 1.21 meters above the traveled way. Any horizontal clearance less than the minimum required for the bridge's roadway width (as shown in Table 5-8) is underlined. Unlimited clearance is indicated by the symbol .
  • Column 4. Record under-bridge clearance, in meters. It is the clear distance between the underside of each span and the surface of the water. The height above the streambed and the height above the estimated normal water level (pertaining to the appropriate bridge type) are included in this column for each span.
  • Column 5. Record the number of spans. Spans are listed in sequence starting from the west. If the bridge is oriented more north to south, start with the northern most span and work south. Place the letter N in column 5 before the span and list in sequence.
  • Column 6. Record the type of span construction. Refer to the diagrams in Figure 5-41 and Table 5-9 for this information.
  • Column 7. Record the type of construction material. Refer to Table 5-10 for this information.
  • Column 8. Record span length, in meters. This is a center-to-center spacing between bearings. The sum of the span length may not equal the overall length. Spans that are not usable because of damage or destruction are indicated by the pound symbol (#), placed after the dimension of the span length. Spans that are over water are indicated by placing the letter W after the dimension of the span length (see Figure 5-42).

Table 5-10. Construction material

Material of Span Construction

Letter Symbol

Steel or other metal

a

Concrete

k

Reinforced concrete

ak

Prestressed concrete

kk

Stone or brick

p

Wood

h

Other (to be specified by name)

o

Figure 5-41. Typical bridge spans

Figure 5-42. Sample Bridge Reconnaissance Report with full NATO symbol

OTHER INFORMATION

When an abbreviated bridge symbol is used or when a recon mission requires it, columns are added to give the MLC, overall length, roadway width, overhead clearance, and bypass possibilities (specify use easy, use difficult, or use impossible). Do not forget to indicate whether the bridge is simply supported or continuous (see Figure 5-43).

Figure 5-43. Sample Bridge Reconnaissance Report with abbreviated bridge symbol

BRIDGE SKETCHES

Show as much information as possible when sketching the bridge on the backside of DA Form 1249 (see Figure 5-44).

Figure 5-44. Sample bridge sketch on Bridge Reconnaissance Report

BYPASSES

Bypasses are detours along a route allowing traffic to avoid an obstruction. Bypasses limited to specific vehicle types, such as those capable of swimming or deep-water fording, are noted on the recon report. Bypasses are classified as easy, difficult, or impossible. Each type of bypass is represented symbolically on the arrow extending from the tunnel, ford, bridge, or overpass symbol to the map location (see Table 5-11).

Table 5-11. Bypass symbols

Bypass easy. Use when the obstacle can be
crossed in the immediate vicinity by a US 5-ton
truck without work to improve the bypass.

Bypass difficult. Use when the obstacle can be
crossed in the immediate vicinity, but some work to
improve the bypass is necessary.

Bypass impossible. Use when the obstacle can be
crossed only by repairing or constructing a feature
or by detouring around the obstacle.

A bypass is considered easy when the obstacle can be crossed within the immediate vicinity by a 5-ton vehicle without work to improve the bypass. The bypass is considered difficult when the obstacle can be crossed within the immediate vicinity; however, some work is necessary to prepare the bypass (ensure that the estimation of time, troops, and equipment necessary to prepare the bypass is included on the recon report). The bypass is considered impossible when the obstacle can be crossed only by repairing the existing bridge or tunnel, building a new bridge or tunnel, or providing a detour.



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