It is important to me to get a seat when I’m travelling by train in the rush hour. This means getting on board without having to indulge in fisticuffs and that, in turn, means that when a train stops, I need to be standing by the doors.
The trouble is that trains seem increasingly to come to a stop with a positional error of more than a few metres, so I miss the chance to park my rear end.
Today’s invention is a device, something like the toe-operated calculator described in ‘The Newtonian Casino. ‘
As a train passes me on the platform, I shine a torch at the windows of the first carriage. This torch incorporates a light sensor which allows a processor to count the number of seconds it takes for each of say three windows to pass (by noting the dark periods during which the light fails to reflect off them).
This allows a deceleration graph to be obtained and used to predict where the carriage doors will end up in relation to my current position. Before the train stops, the torch emits a directed flash which illuminates briefly a spot on the platform where the doors will stop and to which I can preemptively sprint.