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Rh more account for 2,123 miles, and similar streets in smaller incorporated places add 492 miles.

The balance—5,526 miles or nearly 68 percent of the 8,141-mile total—is on rural sections of the interregional system, and includes all rural sections of the system that serve traffic in excess of an average of 10,000 vehicles per day. This high-volume mileage totals 532 miles. The rural mileage within the zones of city influence also includes 3,558 miles or 48.3 percent of the 7,363 miles of rural sections that carry traffic averaging between 3,000 and 10,000 vehicles per day.

These 2 rural mileages—532 miles and 3,558 miles—comprise 74 percent of the total rural mileage within the zones of influence of cities of 10,000 or more population, and serve traffic well above the average daily volume for all rural sections of the system.

The remaining 26 percent of the rural mileage within these zones, or 1,436 miles, carries traffic averaging less than 3,000 vehicles per day.

Nearly a third of this latter mileage, however, carried traffic in 1941 in excess of the approximately 2,600 vehicles per day average for the rural system as a whole.

The more heavily traveled of the rural sections that lie outside the zones of traffic influence of cities of 10,000 or more population, total 3,624 miles and carry traffic averaging 4,809 vehicles per day. By far the greater part of the rural mileage lying outside these zones—a total of 20,300 miles—carries traffic averaging less than 3,000 vehicles per day. The average for the entire 20,300 miles is only 1,531 vehicles per day.

Most of these facts are tabulated in table 10 for the entire United States, and in tables 11 and 12 by geographic regions.