Upon the miasma of midnight, a darkling spirit identified as Roger T.
gently breathed:

Irrelevant. We know that with the brakes applied traction power
cannot be obtained.

Does this mean that any brake application automatically cuts traction power?

I believe the systems are set such that as soon as the brake pressure or
vacuum drops (or rises) beyond a certain point, power is automatically
cut and cannot be reapplied until the brake is restored.

It's typical in North America to "power brake". In power braking, the
throttle is left in notch two or three, the independent brake in full
release while the train is brought to a stand with the train brake working
against the throttle. Is this not possible in the UK?

I can see the advantages of this on very long freight trains, even with
continuous brakes there must be a lot of slack in a mile long train, but
your later post said it was common on passenger trains too - any idea
why? I don't see any advantage to it on something like an HST, where
the control layout ensures that brake valves open and shut
simultaneously at front and rear powercars, and there is no slack worth
speaking of in the 8 coach formations. Even in the days of 15 coach Mk1
rakes, it wasn't, AFAIK, possible. Possibly north American couplers
have more slack than UK ones do? The buckeyes fitted as standard from
Mk1 onwards are 3/4 scale copies of the US ones, though, and of course
until just a few years ago (and still, on railtour stock) the loco is
attached via screw-link over the drawhook with buffers extended to take
the compression.

Btw, what is the independent brake? We tend to have straight-air on
locos, and automatic air or automatic vacuum on the train.

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