"These are much more complicated questions than those about individual journeys, but one thing they all have in common is transport: can I get to and from the places I'm considering quickly and easily?"
The maps on this page show one way of answering that question. Using colours and contour lines they show how long it takes to travel between one particular place and every other place in the area, using public transport. They also show the areas from which no such journey is possible, because the services are not good enough."
(Src. Boing Boing)