Oklahoma highway patrolman Clinton Riggs was a student at the Northwestern Traffic Institute, now the Center for Public Safety, in 1939 when he created the yield sign as a class assignment. His goal was to improve public safety and determine liability in an accident.
In 1950, as a member of the Tulsa Police Department, Riggs placed the first yield sign at the most dangerous intersection in the city. Within a year, the number of accidents fell to zero, and yield signs soon appeared at intersections across the country.
Riggs, who retired as the administrative assistant chief of the department in 1970, was also credited with the integration of the department, developing the Tulsa Police Academy and authoring several laws, including one that prohibits convicted felons from carrying firearms.