In many parts of the GB network, once you get more than a minute or two late you end up with delays propagating throughout the network, because enough is timeta

In many parts of the GB network, once you get more than a minute or two late you end up with delays propagating throughout the network, because enough is timetabled with lines near capacity. You get up to about ~82% within 3 minutes and ~88% within 5 minutes. Beyond that you see little gains.