Highways
Early in the
20th century, most of the streets and roads in the U. S. were made of dirt,
brick, and cedar wood blocks. Built for horse, carriage, and foot traffic, they
were usually poorly cared for and too narrow to accomrrmdate(容纳) automobiles.
With the increase in auto production, private turnpike (收费公路)
companies under local authorities began to spring up, and by 1921 there were
387, 000 miles of paved roads. Many were built using specifications of 19th
century Scottish engineers Thomas Telford and John MacAdam (for whom the macadam
surface is named ), whose specifications stressed the importance of adequate
drainage. Beyond that, there were no national standards for size, weight
restrictions, or com