问题
I want to add some custom roads using google maps api (i.e. off-road routes, gravel roads that aren't marked as roads in the map, etc) and then use those roads in conjunction with existing roads to get directions. I know this isn't possible out of the box, but I wonder if there are any tools, custom implementations or 3rd party libraries to do that.
回答1:
No, there isn't a way to do this at this time. You would have to essentially create your own routing application.
来源：https://stackoverflow.com/questions/9880053/is-there-a-way-to-add-custom-roads-e-g-off-road-routes-to-google-maps-and-the