Page:America's Highways 1776–1976.djvu/411

 upon uniform statewide highway numbering systems. In addition, travelers were greatly aided by the widespread production and distribution of tourist maps that made use of readily identifiable landmarks, as well as route markers and signs. This increased availability of other devices for the guidance of travelers resulted in a marked decline in the use of mileposts, except in a few States and on turnpikes.

An early railroad crossing warning.

Immediately after World War I, as the States engaged in a greatly speeded-up road development program, it became apparent that a simplified and adequate marking system was a necessity. In 1918, Wisconsin decided that proper names could not be applied to an extensive network of highways and so developed the route marker and the numbering method of designating its highways and for directing travel over them. The shape selected for its route marker signs was a triangle with the apex down, using black and white colors. The triangle showed “State trunk highway,” the route number and the State name. Also Wisconsin placed directional and distance signs for the trunk system and for lesser roads.

In 1921 Minnesota established its trunk highway system and promptly installed full-scale marking and signing. Minnesota adopted a star shaped design, with lemon yellow and black colors for all official route signs on the system and suggested white and black for signs placed by other jurisdictions.

In 1911 the road commissioner in Wayne County, Michigan, ordered that a white line be painted down the center of every bridge and curve under his authority. Later, he carried the idea to its logical conclusion and painted the centerline along all the highways. The obvious benefits of the centerline strip were eventually realized, and the striping spread to all highway agencies.

In 1915, a Detroit police official designed the first stop sign. When the first installation proved effective, the city promptly allocated funds to make six major streets through thoroughfares, by placing stop signs on intersecting streets.

Traffic signals were developing in this same decade, first with the hand operated semaphores, then a motorized version that was patented in 1910. The first use of electric traffic signals was during the period 1912 to 1914 with Cleveland, Salt Lake City, and St. Paul all claiming their use to be the first. In 1920, the first three-colored traffic signal light to control street and highway traffic was installed in Detroit. The first four-way three-color signal was installed in Detroit in 1920.

The first traffic control tower, located within an intersection, was set up in 1917, at a main Detroit crossroad. Similar towers also were used about the same time in New York City. 405