After World War I, the race car specifications for the national championship were mostly aligned with what the Indianapolis Motor Speedway wanted to run during its Memorial Day classic, and this still holds mostly true today. AAA, again, restarted the championship with the close of the war for the 1946 season and continued uninterrupted through 1955. After that season, AAA completely pulled out of auto racing, citing the Le Mans disaster and the death of Bill Vukovich at Indianapolis as contributing factors. The United States Auto Club filled the void left by AAA's departure. During the last half of the Racing Boards existence they sanctioned many forms of racing such as midgets, sprint cars, sports cars and stock cars as well as top level championship car racing.