Store Locator Plus searches are based on Radius. Not roads that go around the mountain or over terrain. How would you know which direction mileage to provide if the person doing the search checks “do not allow my location to be shown” for instance. Or if there are two or three stores within 5 miles from them, which mileage per which route in which direction do you show them? What if they can take two different routes to get to their destination, for instance they want to take the scenic route or do not take highway route 1 and want to travel down route 17 instead…? Even Google directions allows you to select a different route. As you can see there are too many variables and dependencies to make this solution one size fits all.
You might be able to write some code for your particular wants or needs but it is not something in the regular base plugin or add-ons. The closest thing with that type of logic would be territories in the Premier plug in There was a lot of complex coding and logistics built into that one feature with oodles of developer hours to design that one little feature.
How search works