Sunday, July 13, 2008

User ballistics

'User ballistics' is a term I sometimes find myself using to describe the movement of people around environments. It's important for the placement of signs, and suggests that, as well as a logical analysis of decision points and sight lines, you need to take account of users' initial trajectory, speed and momentum.

David Lewis and I came up with the term about ten years ago, when researching and advising on the placement of flight information displays in Gatwick Airport. Observing people entering the airport concourse from the train station, we found they came through in bursts (all having arrived on the same train) and were impelled into the room by the momentum of the crowd. Often they progressed 20 or 30 metres into the concourse before they had a chance to stop and look around. At this point they had missed the flight information screens, which were placed to be visible if you looked to the left just a few metres from the door.

As well as the push effect of the crowd, we also found distant features to have magnetic force. At this same point, a very large flight information wall was visible, but not legible. People would walk towards it, but stop at a certain point when the word 'Arrivals' became visible. Those wanting Departures would then turn and look for another direction.