Wiener Übereinkommen
The United States is among the many countries that have not ratified the Vienna Convention on Road Signs and Signals. The first edition of the MUTCD was published in 1935, 33 years before the Vienna Convention was signed in 1968. The MUTCD differs significantly from the European-influenced Vienna Convention, and an attempt to adopt several of the Vienna Convention's standards during the 1970s led to confusion among many American drivers.