TM 5-822-2/AFM 88-7, Chap. 5
Group 1.
Passenger cars, panel trucks, and
for-one basis. Traffic composed of tracked vehicles
pickup trucks
exceeding 40,000-pound gross weight has been divided
Group 2.
Two-axle trucks
into the following three categories:
Maximum Vehicle Gross Weight, pounds
Group 3.
Three-, four-, and five-axle trucks
Category
Tracked Vehicles
The design weights for various pneumatic-tired vehicles
have been based on average weights, as determined
V
60,000
from Federal Highway Administration traffic surveys
VI
90,000
made on public highways, plus one-fourth of the
VII
120,000
difference between these average weights and the
Forklift trucks exceeding 10,000-pound gross weight are
maximum allowable weights. For group 2 and group 3
treated in TM 5-809-12/AFM 88-3, chapter 15.
vehicles, maximum allowable weights are based on
(9) Design index for Army and Air Force
single-axle and tandem-axle loadings not exceeding
pavements. The design of pavements for Army and Air
18,000 and 32,000 pounds, respectively. Since traffic
Force roads, streets, and similar areas is based on a
rarely will be composed of vehicles from a single group,
"design index," which represents the combined effect of
pneumatic-tired vehicular traffic has been classified into
the loads defined by the traffic categories just described
five general categories based on the distribution of
and the traffic volumes associated with each of the
vehicles from each of the three groups listed above.
lettered classifications of roads or streets. This index
These traffic categories are defined as follows:
extends from one through ten with an increase in
Category I.
Traffic composed primarily of
numerical value indicative of an increase in pavement
passenger cars, panel and pickup trucks (group
design requirements. Table 3-2 gives the appropriate
1 vehicles)
but containing not more than 1
design index for rigid pavements for combinations of the
percent two-axle trucks (group 2 vehicles).
eight traffic categories based on distribution of traffic
Category II.
Traffic composed primarily of
vehicle type and the six letter classifications based on
passenger cars, panel and pickup trucks (group
the volume of traffic. For flexible pavements, the design
1 vehicles), but containing as much as 10
index method is covered in TM 5-822-5/AFM 88-7, Chap.
percent two-axle trucks (group 2 vehicles). No
3. For example, suppose an ADT of 2,000 vehicles
trucks having three or more axles (group 3
composed primarily of passenger cars, panel trucks, and
vehicles) are permitted in this category.
pickup trucks (group 1), but including 100 two-axle trucks
Category III.
Traffic containing as much as
(group 2) is anticipated for a road in flat terrain. First,
from b.(3) above, the 100 trucks are equivalent to 200
15 percent trucks, but with not more than 1
passenger cars, giving an effective ADT of 2,100. The
percent of the total traffic composed of trucks
effective DHV is then 15 percent of 2,100, or 315,
having three or more axles (group 3 vehicles).
Category IV.
making this a class D facility. Second, the group 2
Traffic containing as much as
vehicles are 100/2,000 or 5 percent of the total of groups
25 percent trucks, but with not more. than 10
1 and 2, making this category II traffic. Therefore, the
percent of the total traffic composed of trucks
appropriate design index from table 3-2 is 2.
having three or more axles (group 3 vehicles).
(a) Tracked vehicles. Provision is made
Category IVA. Traffic containing more than 25
whereby the designer may determine pavement design
percent trucks.
requirements for tracked vehicles in combination with
(b) Tracked vehicles and forklift trucks.
traffic by pneumatic-tired vehicles or for traffic by tracked
Tracked vehicles having gross weights not exceeding
vehicles only. Where both pneumatic-tired vehicles and
15,000 pounds and forklift trucks having gross weights
tracked vehicles are to be considered, the proper letter
not exceeding 6,000 pounds may be treated as two-axle
classification of the road or street is determined
trucks (group 2 vehicles) and substituted for trucks of
according to the total volume of traffic from both types of
this type in the traffic categories defined in (a) above on
vehicles. In most cases of traffic combining pneumatic-
a one-for-one basis. Tracked vehicles having gross
tired vehicles with tracked vehicles having gross weights
weights exceeding 15.000 pounds but not 40.00 pounds
in excess of 40,000 pounds, the determination of the
and forklift trucks having gross weights exceeding 6,000
appropriate traffic category will be governed by the
pounds but not 10,000 pounds may be treated as group
tracked vehicle component of the traffic In table 3-2 the
3 vehicles and substituted for trucks having three or
more axles in the appropriate traffic categories on a one-
3-6
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