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Why You Can’t Reverse a Route

Sep
23
2010

A question that comes up again and again in our GPS Discussion Forums is Why can’t you reverse a route? A similar question with virtually the same answer is Why does my GPS pick a different route when going back to the original starting point? People often notice that a GPS might pick a different route from point B to point A than it does from A to B. Why is this? There are a few reasons.

The simplest answer is that it is simply a different route. When the GPS calculates a route and computes directions it is doing so only in one direction. So when you get to point B and want to get back to point A it needs to generate a new set of directions. But why does it sometimes take a different route? Here are a few reasons.

One Way Roads

If your original route contains one way streets then it obviously can’t go the same way for the return trip.

Interstates, Freeways

Keep in mind too that many Interstate Highways and Freeways are also “one way” streets and thus new directions need to be calculated. Another factor is that with a typical “clover” style exit traveling from the West and headed North you will travel further than you would going the opposite direction coming South and exiting to the West. That extra distance could cause a different route to be more efficient.

Turn Restrictions

Many intersections have turn restrictions where a left turn might not be allowed, but a right turn is permitted. Thus this could cause a different route to be more efficient.

Crossing Lanes

In North America a left turn often takes longer than a right turn because you need to cross more lanes of traffic. On a four lane road when turning left you need to fully cross two lanes and merge into a third lane. While turning right there are no lanes to cross and only a merge into the lane furthest right. So some GPS devices might account for this and take a route that slightly favors a right turn.

Time of Day

Newer GPS devices on the market today build routes based on time of day and predicted (rather than live) traffic. So if you go from A to B during a slow time of day but go back to point A during rush hour the GPS might pick an entirely different route based on predicted traffic patterns.

So each of these factors, and possibly others, account for why a GPS might not take the same way back to the starting point as it did going to your original destination.

5 Responses


  1. I’ll add one more reason: Sometimes there is simply no logical reason. Case in point: I used to commute back and forth on weekends between my apartment in NJ and my parents’ house on Long Island. I know what the quickest way to go is and that was the way it would always tell me to go when starting on Long Island. However, when starting from NJ it would always try and route me out of my way and through Manhattan. Didn’t matter what time of the day was involved. Going the preferred way was always the fastest and there were no real one-way streets or illegal turns involved. I came to the conclusion that my HP is just a little tech’d in the head.

    patruns - September 24th, 2010
  2. I think the point is that it would be nice to have a button that said “Reverse Route” or something along those lines.
    Here’s a personal example. A friend of mine gave me directions to his house, and I simply asked him for his address to put into my gps. He told me “don’t follow your gps, it will take you through an area with train tracks and it’s always much faster to come across the viaduct and then trace back down to my house”. So when using local knowledge of a small detailed area, rather than having to ask for directions back out I’d like to have my gps “attempt to its best effort” to take me back the way I came.

    dodgypete - December 4th, 2010
  3. There should be a return the same route option, what the heck is wrong with these programmers that they don’t listen to what the consumer wants? I hear this all the time and I’ve experienced it with maddening frequency I get routed through downtown traffic on a return route where I arrived on interstates!!! Not buying your explanation of more efficient or whathaveyou, it needs to be fixed!

    Elizabeth - May 27th, 2011
  4. There should be a reverse route function to allow some flexibility.

    Let’s say you prepared a route from Alpha point to Beta point with several Via’s along the way to see some scenic areas. Now if there were a change in your itinerary which had put you closer to the Beta point and you now want to take that route but in reverse from B to A and all the intervening vias.

    I would certainly want a button to reverse the order of that route rather than have to plug in all the information again in reverse order. That data was previously there, so why must I re-enter it again, but in reverse order? Isn’t that what computers do so well?

    bob - June 17th, 2011
  5. Is there a reverse/return route on any Garmin model for off the road use. We plan to use it in the dessert?

    Ruth - November 30th, 2011



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