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Rh They are designed for normal highway operation and compare in size and weight with the civilian trucks and combination units in common use. The second group includes a relatively small number of military vehicles which are designed and intended to meet specialized requirements for which no general-purpose vehicle chassis can be adapted. Tank transporters and tanks are examples of vehicles in the second group. Frrequent use of highway facilities by these vehicles is not expected.

The limitations of size and weight placed on military general-purpose and special-equipment vehicles by Army Regulation No. 7 S-105 are summarized in table 11.

The general-purpose limits exceed those recommended by the American Association of State Highway Officials only in the length and maximum gross weight permitted for combinations other than tractor-semitrailers.

The greater length permitted (65 versus 60 feet), in view of the probable small numbers of vehicles of the permitted dimension, will present no serious traffic problem on existing roads and will require no alteration of new road design standards adequate for 60-foot combination vehicle length.

The greater maximum gross weight permitted (78,000 versus 72,600 pounds) is consistent with the greater length limitation. Vehicles conforming to these greater limits of length and maximum weight will generate in H15 bridges approximately the same stresses as vehicles conforming to the lesser limits of length and weight recommended by the association.

For the various special-purpose vehicles for which the Army regulations permit designs exceeding in dimensions and weight the limits prescribed for vehicles intended for regular highway use, considerations of combat effectiveness are paramount in the determination of size and weight. Their occasional regulated use of roads in times of peace will present no serious traffic problems and all lesser considerations of convenience, necessity, and economy must yield to their exigent use in war.