I did a quick search of the top secret website (you know, Google) and found this with the search terms 'Troop Capacity Army Vehicles' and here ya go. It didn't copy and paste that well but here it is.
TB 9-639
DEPARTMENT OF THE ARMY TECHNICAL BULLETIN
PASSENGER-CARRYING CAPACITY OF TACTICAL AND ADMINISTRATIVE VEHICLES COMMONLY USED TO TRANSPORT PERSONNEL
Headquarters, Department of the Army, Washington, D.C. 9 NOVEMBER 1988
This manual supersedes TB ORD-639 dated 15 May 1956
1. Purpose. The purpose of this bulletin is to provide information to authorized personnel on the
passenger-carrying capacities of tactical and administrative vehicles commonly used to transport personnel.
2. General. The passenger-carrying capacities listed below are for normal passenger-carrying operations and
are consistent with safety policies and design features of the vehicles. The passenger capacities apply only
when the vehicle is properly equipped with permanent or temporary seats.
3. Passenger-carrying capacities
NOTE
The passenger capacity indicated does not include the operating crew.
Passenger-Capacity
Vehicle
a.
14
2 1/2 Ton Cargo Truck
18
2 1/2 Ton Extended Cargo Body Trucks
10
2 1/2 Ton Dump Trucks
16
5 Ton Cargo Trucks
20
5 Ton Extended Cargo Body Trucks
12
5 Ton Dump Trucks
8
5/4 Ton HMMWV Troop Carrier
4
5/4 Ton HMMWV Cargo/Troop Carrier
8
5/4 Ton M880, M881, M882
80
Semitrailer Personnel Van
b. Passengers, who are not crew members and carried in the cab of the vehicle, are limited to available seat
belt positions.
c. The passenger capacity of sedans, vans, station wagons, and other administrative vehicles is limited to
the number of seat belt positions.
d. Refer to the operator's manual and AR 385-55 for vehicles not listed. Do not crowd passengers on bench
type seats in cargo beds.
e. Passengers may be transported on post without fixed seats for short distances, under 10 miles,
provided each passenger remains seated wholly within the body and the body is equipped with stakes or
sideboards. Canvas tops will be in place with sides rolled down when cargo space is used for passengers.
NOTE
The driver is responsible for the safety of the personnel riding on their
vehicle. Drivers will refuse to move a vehicle if anyone is in an unsafe
position or the vehicle has too many passengers.
Approved for public release; distribution is unlimited.