Route change on the American freeway system

The first elements of the American freeway system were built in the 1920s and now comprise over 59,000 miles of roads. In addition to growth in the system at both the national and urban levels and increases in capacity, over five hundred miles of freeways have been relocated. These route changes have previously escaped attention from researchers. A database of all route changes on the Interstate system and other freeways was compiled in GIS and analyzed. Route changes are due to the need to replace old and obsolete bridges and tunnels, rebuild sharp curves or steep grades, and eliminate substandard sections. These route changes are overwhelmingly urban in nature. New relocations will appear as the American freeway system ages and continues to adapt to changing conditions. Some bypassed sections of freeways may eventually become tourist attractions.