Class 1 highways had one- or two-digit numbers, while Class 2 highways had three-digit numbers. For example, routes 1 and 57 were Class 1 highways while 507 (the one with the highest number) was a Class 2 highway. A 1964 amendment to the governing law resulted in a unification of the classes, which took effect in April of the following year. Highways numbered since that time have had three-digit numbers, so the numbers 58-100, which had so far been unused, remained unused. However, when Okinawa Prefecture reverted to Japanese control in 1972, Route 58, with its southern endpoint in Okinawa's capital city of Naha, was established. The numbers from 59 to 100 remain unused. Some other numbers have been vacated by the joining or changing of routes: 109 (joined with 108), 110 (renumbered as 48), 111 (renumbered as 45), 214-216 (joined to form 57).