1933 Virginia state highway renumbering

In 1933, the U.S. state of Virginia renumbered almost all of its state highways. This renumbering was caused by the assignment of numbers from 600 up to the new secondary system, but all three-digit numbers were affected. At the same time, all numbers that conflicted with U.S. Routes - except State Route 13 - were renumbered, and all long overlaps with U.S. Routes were eliminated. Several new routes had the same numbers as U.S. Routes and served as their extensions.

Prior to 1933, routes were assigned by district. Two-digit routes generally crossed district lines, while three-digit routes were assigned with their first digit as the district number. The new system also grouped routes by district, but not as strictly (these routes could cross lines) and with no room for expansion; thus additional routes, starting later in 1933, often received numbers from 283 up.

...
Wikipedia