Most VoiceMap follow a set route, starting from a specific point, and this is how we can match audio times to travel times and include turn-by-turn directions
No – at least not in the case of the vast majority of tours, and when this is possible, it is clearly stated in the tour description.
VoiceMap's tours almost all include turn-by-turn directions, and if you started a tour at the end and did it in reverse, left turns would become right turns.
Beyond that, the tours are all carefully timed so that audio duration matches travel duration. This means that the audio that starts automatically at point X is under two minutes if the walk to point Y is two minutes, but the same is not true in reverse. The audio for Y might be 3 minutes because the walk to point Z takes that long, and so if you go in reverse it would still be playing by the time you arrived at point X.
But finally, and most importantly, because we've built the experience around giving directions and timing the audio, the playback is also sequenced for better accuracy, so automatic playback won't actually work at all in reverse.