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The grade on U S Route 70 averages almost 11 percent for a distance of 0.15 mile. The up-and-down hourly traffic on this grade in 1948 was 555 vehicles. The street has a 55-foot concrete pavement.

Photo by Norman G. Wallace

The longest grade

The longest grade on the entire system is on U S Route 99, south of Bakersfield, Calif. It is 20 miles long and averages 4 percent over the entire length. Included, however, are two 6-percent grades, totaling more than 6 miles, and two 5-percent grades, totaling one-half mile.