Page:Highways for the National Defense.pdf/13

12 Military traffic was observed to have about the same effects as ordinary civil traffic, and the damage done during maneuvers was in all probability no greater than would have resulted from an equally intensive use by civil traffic.

Observations in the States of Washington, Wisconsin, New York, Texas, and Louisiana showed that main highways already giving reasonably adequate service to substantial volumes of civil traffic were not damaged by military traffic. Addition of the military traffic to the normal civil traffic on the highways caused some inconvenience and delay to the latter, and on nan-ow surfaces some damage to road edges and shoulders resulted.

County and town roads in combat areas suffered damage principally because they were of light construction not designed for the intensive use to which they were subjected during maneuvers. In addition, three unusual features connected with the military use contributed to the damage: (1) Use of tire chains by trucks; (2) use of large numbers of iron-shod cavalry horses; and (3) maintenance operations were either suspended entirely or were not as intensive as the greater use required.

Damage was reported to dirt roads, gravel roads, and thin bituminous treatments on light bases, the latter suffering damage to both surfaces and bases. Failure of a few pipe and wooden culverts on county roads occurred in Wisconsin. In Louisiana the cost of necessary repairs was estimated at $68,000. In Texas the cost of repairing extraordinary damages as reported by the State highway department was $140,000.

The New York, Wisconsin, and Washington maneuvers were held in the summer when there was no extended period of rain. Even at the time of the spring maneuvers in Louisiana and Texas road subgrades were comparatively dry. It is probable that damage to light surfaces would have been greater had the maneuvers occurred in wet or thawing weather.

Plans of the War Department are not yet sufficiently revealed to determine the mileage of roads that will be subjected to tactical uses; but the obligation of the Federal Government to make adequate provision for necessary improvements of roads thus regularly used and for the repair of damage caused by similar occasional uses is apparent.

The strategic network.—The condition of the main lines of the strategic network in rural areas has been surveyed in detail by the Public Roads Administration and the State highway departments, and the results of these surveys have been recorded on sectional graphs, of which a typical example is presented in plate 5.

On the basis of these surveys and the design requirements for adequate accommodation of both civil and defense traffic on each section of the network, it has been determined that the most critical deficiencies of the rural sections of the network consist of 2,436 bridges of load capacity inferior to the H–15 loading standard, which is a minimum requirement from both civil and defense standpoints. There are also on the network in rural areas approximately 5,090 miles of road with present surfaces less than 18 feet wide, and approximately 14,000 miles on which the existing surface is incapable of supporting in all weather, vehicles of 9,000 pounds wheel load, equipped with low-pressure pneumatic tires.