These routes for heavy traffic should be properly sign-posted; and information concerning then should be circulated throughout the command. It will evidently be impossible to provide all routes with the heaviest bridges; hence a rigid traffic supervision should be exercised to prevent heavy vehicles from wandering into the minor routes where the bridges have not sufficient strength to carry the loads that would thus be imposed upon them.

The foregoing requirements conflict to some extent with the previous statement that a hasty bridge should be built with a low factor of safety and to meet the exigency of the moment only. Most bridges constructed for tactical uses will be off the main routes of transport. In any case, the engineer must decide whether the probable future service justifies the expenditure of more time in initial construction.

In the operations of the large, fully-equipped, modern army, standardized steel superstructures, capable of carrying its heaviest loads, will hereafter be characteristic of all important routes of transport, even quite close to the front. In the operations of small, detached, rapidly-moving, and lightly-equipped forces in a sparsely settled country, the lighter forms of floating bridge, and various kinds of improvised structures to carry moderate loads, will in the future, as in the past, be typical of bridging activities. In any campaign, improvised structures will always be required in the combat zone.

Transportation of Materials

There is always a shortage of transportation for every purpose in time of war. Such important supplies as ammunition, weapons, and food must naturally take precedence over construction materials. When the necessity for a bridge can be foreseen for a reasonable time, it may be practicable to assemble in advance the plant and material requisite for its erection. This will often be possible on the lines of communication; but at the front it will be absolutely impracticable to have on hand, at every locality where an emergency may demand a bridge, all the materials required for the standardized design. The engineer is thus compelled to improvise and adapt to his needs such miscellaneous material as he can secure on short notice, locally or otherwise.

Where military activities can be foreseen, depots or "dumps" of construction material are assembled in the vicinity, so that only local transport will be required. Large, heavy, awkwardly-shaped pieces will always be delayed in transport. They are difficult to load and ship; moreover, they arouse the hostility of the transport personnel, who have a natural tendency to push them towards the bottom of the "priority list"; hence, all bridge material should be of a size and weight that will insure reasonable promptness in transportation.

While it will seldom be possible to supply the engineer with everything that he needs, it will often be practicable to provide certain materials that