Creation of Interstates

 In 1941, President Roosevelt appointed a special committee to explore the idea of a "national inter-regional highway" system, but the committee's progress was halted by the initiation of World War II. After the war was over, the Federal-Aid Highway Act of 1944 authorized the designation of what are now termed "Interstate Highways", but did not include a funding program to build the highways. Limited progress was made until President Dwight D. Eisenhower renewed interest in the plan in 1954. This began a long, bitter debate between various interests such as rail, truck, tire, oil, and farm groups, over who would pay for the new highways and how.  After compromises had been made, the Federal-Aid Highway Act of 1956 authorized the construction of the Interstate Highway System, an interconnected network of controlled-access freeways that allowed larger trucks to travel at higher speeds through rural and urban areas. This act also authorized the first federal maximum gross vehicle weight limits for trucks, set at 73,208 pounds (33,207 kg). In that same year, modern containerized intermodal shipping was pioneered by Malcom McLean, allowing for more efficient transfer of cargo between trucks, trains, and ships.

In the late 1950s, the American Association of State Highway and Transportation Officials (AASHTO) conducted a series of extensive field tests of roads and bridges to determine how traffic contributed to the deterioration of pavement materials. These tests led to a 1964 recommendation by the AASHTO (to Congress) that the gross weight limit for trucks should be determined by a bridge formula table based on axle lengths, instead of a static upper limit.^[2] By 1970 there were over 18 million trucks in America.