Page:America's Highways 1776–1976.djvu/392

 going to the market center. One critic claimed that the center was the most desirable position because it was better looking, was more easily drained, and was safer to traffic.

The dilemma as to the most suitable position for single-lane pavements was soon resolved—the rate of traffic growth was so rapid that single-lane pavements were short lived and such construction was uneconomical. Consequently, this type construction was discontinued. The Federal Highway Act of 1921 doubtless spurred this action. This legislation required, for the first time, that the wearing surfaces on Federal-aid highways be at least 18 feet wide.

With the discontinuance of single-lane construction, practically all subsequent paving between 1920 and 1930 was of two-lane width, ranging from 14 to 20 feet. Pavements wider than two lanes were rarely needed. The experience in Maryland may be typical. In 1920 the concrete roads were constructed 15 feet wide, 6 inches in depth at the edges and 8 inches in depth at the center, resulting in a crown of 2 inches. This same type construction was used in 1921. In 1922 the Commission thought it desirable to reduce the crown and adopted a section 6½ inches in depth at the edges and 7½ inches in the center. This construction method was used in 1922 and 1923. At that time, however, concrete was finished by hand, and some difficulty was experienced in getting a smooth road with only a 1-inch crown. In 1924 the Commission went back to building a 2-inch crown, still using a 15-foot width, 6 inches in depth at the edges and 8 inches at the center. This type construction continued to the end of 1927. In 1928 the thickened edge was adopted, and the standard width of roadway was increased to 16 feet with a depth of 9 inches at the edges and 6.3 inches at the center and was the method still used in 1930.

In contrast, Illinois during this period was building concrete pavements 18 feet wide (in some cases 20 feet) on a roadway 30 feet wide. In 1926 Illinois constructed its first four-lane highway. Lanes 10 feet or more in width were rare anywhere in the country.

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