A three-digit interstate or 3di is an Interstate Highway that acts as a loop, bypass, or spur from a main Interstate route (known as a one or two-digit interstate). Three-Digit Interstates that begin with an even number are generally routes around or through cities, and routes that begin with an odd number are generally routes that spur into cities or reach areas not located near the main Interstate. The term "three-digit interstate" was coined by Scott Oglesby, who originally cataloged them all at Kurumi.com.