How are distances listed on freeway signs between cities determined?
Do you ever wonder how the miles between cities are calculated for freeway signs? There are a lot of questions that go along with this idea, like what do the distances measure? When a sign says, for instance, that you have 10 miles to drive until you reach St. Louis, does that mean to the center of the city, or to the first exit, or to the city limits? In an interview with a CalTrans employee (CalTrans is the company that creates and maintains California roads and so on), he said that the company measures the distances by driving and recording the miles on the odometer. There are also markers every mile along some freeways and highways. As far as what the numbers represent on those signs you see, CalTrans said that they consider what part of the city travelers would be most interested in getting to, which is usually the center of the city. The first exit into the city is the alternative destination a freeway sign will prep a driver for. So as you can see, it’s actually pretty arbitrary
