Reconnaissance trucks, designed for the United States army, run the gauntlet of grueling tests to prove themselves fit for field service. The olive drab vehicles have four-wheel drives, must maintain a top speed of forty-five miles an hour on the level, and the fuel systems cannet falter on steep slopes or roughest terrain. To meet rigid army requirements, the light half-ton trucks, loaded with one thousand pounds, must be able to climb a sixty per cent grade in low gear, a seven per cent grade in high gear, and a five per cent grade - towing an extra thousand-pound load - in high gear. Carrying three thousand pounds, the one and one-half ton trucks must go up the sixty per cent grade in low, a five per cent grade in high, and, with an additional four-thousand pound tow-load, climb a three and one-half per cent grade in high.