That ' s exactly why giving the distance is less useful than the time spent driving . 20 km could take an hour or 20 minutes depending on where you are . I repeat myself you often have the option to take a major highwayautobahn , where you can cover three times the distance in the same it takes on the other streets . And this argument is beside the point Fair , but city driving consumes way more gas than highway driving , so it ' s still not a constant metric . It ' s not about being constant , it ' s about being generally so expensive that it ' s a huge factor in any consideration regarding driving anywhere . Partly because we have fairly useful public transportation available , so people might decide to rather use that to cover bigger distances or those that go through major traffic areas . If I say it takes 45 minutes from A to B , that would get me 10 km if I have to get through Frankfurt during rush hour . It gets me 100 km if I drive that distance on the autobahn , and more if I have a fast car and like to use it . It gets me ? distance when using public transportation . It ' s simply to malleable a factor to give a true indication of how far something is away . So for us , measuring by time isn ' t useful because it gives less information than measuring distance . For you , it ' s reversed . For each concept , you have to know something about the context of why the different methods make more sense , and until you do , you ' ll take your own method as standard and most useful , as you are doing right now .