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David Cantrell · February 18th 16, 02:24 PM posted to uk.transport.london

On Wed, Feb 17, 2016 at 05:04:50PM +0000, d wrote:
On Wed, 17 Feb 2016 16:33:55 +0000
Mike Bristow wrote:
I don't have a good grasp of the cost/benefit ratio of your proposed
scheme. I don't think you do, either. But feel free to prove me
wrong by estimating the cost of installing - and maintaing for a
decade, say - a set of points, and the benefit of doing so - again,
expressed in cost terms.
Feel free to tell me why the actual cost matters, rather than as a percentage
of the total cost of the ELLX.

Because you want the actual cost to be equal to or less than the actual
benefit. And because sensible people "look after the pennies and the
pounds will look after themselves".

What's the odd 1% here, 3% there, 0.5% there, 2% there and so on? It's a
50% cost overrun and you'd be screaming and shouting about it.

Don't forget to include the cost of increased delays when the points
fail. Obviously, you'll know the MTBF for points - I'd be interested
in knowing what that is, as it happens, so can you share your
estimate for that, too?
I imagine the MTBF would be the same as other sets on that line.

I expect it wouldn't, simply because stuff that is rarely used will not
behave in the same way as stuff that is often used. The MTBF might be
longer (due to less wear and tear) or it might be shorter (because lack
of use means the mechanism gets gunged up with pigeon **** and dead
mice).

It's also worth noting that because they never get out of the "infant
mortality" part of the bathtub curve, things that arehardly ever used
are rather more likely than you would expect to fail when you need them.

Oh GOOD sigmonster.

--
David Cantrell | Enforcer, South London Linguistic Massive

Good advice is always certain to be ignored,
but that's no reason not to give it -- Agatha Christie