Episode #2.7 - S2-E7
Plot hole: It is established that there are 4 stations in the N, S, E, W parts of the island and it takes roughly the same amount of time to get to any of them from the central part of the island where the university is. When we see a map of the fictional Saint Marie as DI Richard Poole explains how he is going to look for the camera, the map shows an island with a distance W to E about double the the distance from N to S, making impossible that one could get by car to places with such different distance from the center in equal amounts of time. (00:30:50)