> The London underground generally runs at about 24 TPH at rush hour on a single line (in each direction) Not quite. All of the resignalled lines manage more t

> The London underground generally runs at about 24 TPH at rush hour on a single line (in each direction) Not quite. All of the resignalled lines manage more than that. The Central line reaches something between 27 and 30 tph, the Jubilee Line 30 tph (and I think there are still plans to go even higher) and the Victoria Line 36 tph. The Northern Line is a bit special because of its branching, but the single section south of Kennington towards Morden manages 30 tph as well. And even the Subsurface Lines (which for the largest part are still conventionally signalled, although not for much longer) manage around 27½ tph on the north (Baker Street - Aldgate) and south (Tower Hill - Gloucester Road) sides of the circle. > the problem is that as the trains get more crowded, their braking distance increases A properly designed brake system will a) be designed to achieve the required deceleration even under maximum loading b) include load compensation, i.e. the braking force for each car is adjusted depending on its loading to achieve the same deceleration so no, that shouldn't really matter.