(The word "road" is used here to avoid the route/highway argument.)
Knowing the logic behind road numbers can help you navigate when you are lost.
Roads that circumscribe major metropolitan areas have three digits. Thus, 495 circumscribes the Boston area.
Roads that run north/south have odd numbers. Thus, 95 runs from Florida to Canada.
Roads that run east/west have even numbers. Thus, Route 2 runs from Cambridge, out through Williamstown, and beyond. I-40 runs from Wilmington, NC, to somewhere way out west, past Texas. And Highway/Route 66 is perhaps the most famous example of an American east/west road.
Knowing this logic can (sort of) help you navigate when you are lost.
It also helps to know that the numbers increase from west to east and south to north (for interstate highways at least)