from six countries were placed along the road for test subjects to gauge their legibility at a distance. The test strips were located along Ohio State Route 104 near Columbus, U.S. Route 250 and Virginia State Route 53 near Charlottesville, Minnesota State Highway 101 near Minneapolis, and other roads in New York. France, Chile, Turkey, India, and Southern Rhodesia reciprocated by installing MUTCD signs on their roads. In the U.S., the experiments attracted unexpected controversy and curious onlookers who posed a hazard. However, the experiments eventually led to the Vienna Convention on Road Signs and Signals. In 1953, after cooperating with the UN conference's initial experiments, the United States declined to sign or ratify the UN's then-proposed protocol for a worldwide system of uniform road signs. There were two major reasons behind this decision. First, most U.S. roads and streets were (and still are) under state jurisdiction. Second, the United States was developing modern controlled-access highways at the time (culminating in the creation of the Interstate Highway System in 1956), and the novel problems presented by such new high-speed highways required rapid innovations in road signing and marking "that would definitely be impaired by adherence to any international code". In 1960, the National Joint Committee on Uniform Traffic Control Devices was again reorganized to include representatives of the National Association of Counties and the National League of Cities, then known as the American Municipal Association. In 1961, the MUTCD was again revised to make yellow center lines mandatory for the two exceptions where they had previously been recommended. The 1961 edition was the first edition to provide for uniform signs and barricades to direct traffic around road construction and maintenance operations. In 1966, Congress passed the Highway Safety Act, , , which is now codified at et seq. It required all states to create a highway safety program by December 31, 1968, and to adhere to uniform standards promulgated by the U.S. Department of Transportation as a condition of receiving federal highway-aid funds. The penalty for non-compliance was a 10% reduction in funding. In turn, taking advantage of broad rulemaking powers granted in , the Department simply adopted the entire MUTCD by reference at . ((a)(1), also enacted in 1966, authorizes federal agencies to incorporate by reference technical standards published elsewhere, which means the agency may merely cite the standard and need not republish its entire text as part of