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Rh more than 1 in each 1½ miles of the system. All other curvature on the rural system is not greater than 3 degrees.

A 3-degree curve has a radius of about 1,900 feet. It is a curve that can be rounded with safety at 70 miles an hour; but any curvature of greater degree requires for safety a reduction of vehicle speed below 70 miles an hour. On a curve of 11 degrees (radius about 520 feet) it is unsafe to travel above 50 miles an hour. Curves sharper than 11 degrees occur On mountainous sections of the system with a frequency of more than once per mile. About once in each 1⅓ miles in these sections in mountainous areas a curve is encountered which is sharper than 14 degrees, which is safe for a speed of only about 40 miles per hour.

Photo by Tennessee Conservation Department

Curvature and safe speed

If by reason of the frequency of occurrence of curves in excess of 11 and 14 degrees, the mountainous sections of the system in their