The map doesn't guarantee that at all. Two items on the map can appear next to each other and take a very long time to get between -- perhaps they're separated by a freeway that you can't cross, for example.
There are two channels of buses going N-S in the city, and both channels meet downtown. From downtown, two locations can be about equally distant in travel time northwards, and nearby in E-W distance compared to their N-S displacement, but they're separated by a freeway and lie on different N-S channels, and so the E-W distance takes as long to commute (by foot or transit) as going downtown and back northwards would.