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How are distances listed on freeway signs between cities determined?

Updated on October 5, 2012

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 state agency that builds 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. I always thought the distances meant from one city limit to another, but then once I started driving, I realized this was unlikely, as I drove between cities and figured I had driven fewer miles than was indicated on the signs.

I hope this was helpful... a little bit of trivia! This question isn't as relevant for the signs that show how much longer until you reach an exit or junction or so on... those need to be more accurate!


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    • Matthew Cepican profile image

      Matthew Cepican 9 years ago

      I always thought it was from the Post Office...

    • glassvisage profile image

      glassvisage 9 years ago from Northern California

      Thanks ladies! (and gentleman!)

    • Earth Angel profile image

      Earth Angel 9 years ago

      GREAT Hub!!

      I have thought about it a million times!! Alas, I also must have traveled a million miles by car for business!! The distance on the signs never made any sense to me!! Thanks for clearing up that bit of trivia!!

      Blessings always, Earth Angel!

    • SweetiePie profile image

      SweetiePie 9 years ago from Southern California, USA

      Interesting topic. I had not thought about this in awhile, but thanks for answering any question I had about this issue. The picture also is good for grabbing peoples' attention and this hub would make a good discussion on a road trip.

    • lauren.rabaino profile image

      lauren.rabaino 9 years ago from Los Angeles, CA

      strangely, I've always wondered about this...

    • ToddieM profile image

      ToddieM 9 years ago from Diamond Bar, CA

      I bet Las Vegas is calculated via the "first exit" method. Downtown Las Vegas is not where it's at these days.