On Sat, 19 Jan 2008 20:09:35 +0000, asdf
wrote:

On Sat, 19 Jan 2008 19:24:58 +0000, Tom Anderson wrote:

Fair enough, I see your point - and yes, I suppose the Victoria line
can be a bit jerky. Perhaps the new stock on the upgraded line will
manage to do the job in a smoother manner, without sacrificing the
speed.

That seems perfectly possible - they could lower the rate of change of
deceleration, without significantly sacrificing the magnitude of the
deceleration.

You beat me to it! The rate of change of acceleration [1] is known as
'jerk rate',

[1] The fourth derivative of position with respect to time - fourth!

Third, surely?

"In the fall of 1972 President Nixon announced that the rate of
increase of inflation was decreasing. This was the first time that a
sitting president used the third derivative to advance his case for
reelection." - Hugo Rossi, Mathmetician.