How do they come up with freeway numbers? They all sound alike: 5, 105, 405, 605.

    There will be a quiz on this, so pay attention. The California Department of Transportation picks the numbers. I asked how this was done and was pointed to a Web site. It was created by road fan Daniel P. Faigin, who explains that two-digit routes usually have odd numbers if they run north or south and even numbers if they run east or west. Routes numbered with multiples of 5 (I-10, for instance) typically go cross-country. Three-digit routes have odd first numbers if they spur into cities and even first numbers if they loop around cities. Of course, says Caltrans spokesperson Maria Raptis, all of this is open to interpretation and valid “only in leap years.”