question about the S8 stock

They must be very limited then!

It's not just a bunching issue, which is annoying but not a major problem.

The real issue is that if they can exceed the upper performance characteristics of the A stock, there is a risk of compromising signal overlaps which have been calculated assuming A stock speeds and acceleration.

That might be the case, but LU's standards are very explicit that you only use a generic set of brake rates when calculating overlaps; one for surface and one for tunnel.

In reality the brake rate probably isn't any higher for an S than an A (though prjb is more than welcome to correct me). The difference is in the allowance in the overlap calculation for brake build-up time which will probably be faster on an S as it doesn't have to vent all the air from one part of the train line.

So the points made by Tom and Charlie J are that currently the S stock performance has been matched to A stock capability (rather than blanket 50mi/h). Thus the trains have signal overlap compatible performance. The speed that could be reached at a signal is matched to the safety braking distance provided beyond, in case the signal is passed at danger and the brakes automatically applied by the trainstop/tripcock system. All LU passenger stock has basically the same overall emergency braking performance capability. This is fundamentally limited by the steel wheel on steel rail technology the railway relies on, rather than modernity vs. antiquity!
The S stock does have more train performance available for later deployment with a future ATC system designed to use it safely.

Yes, the Correct Side Door Enable beacons for S stock also command the appropriate train performance curve for the area to match whether the older trains should be Flag Up or Flag Down. The Train Oerator gets a visual indicator in the cab when the train is in the equivalent of Flag Up.

You'd have to have every signal with an approach-controlled added if that was the case to satisfy the HSE and whoever-bloody-else.

Probably because the acceleration of the A stocks is slower than the 67s, and, as has already been said above, the performance of the S8s is limited to match that of the A stock.

i see thanks, i guess the met is a much more complicating line in comparison with the vic!

Unless they resignal the line no. Tom said that the overlaps will be based on A stock acceleration, which is a darn sight lower than the S stock will be when uncapped. That's at 100% motored axles vs. the 50% of the A stock, with AC traction for good acceleration across all speeds!

The power upgrade will need to come too as well. Hence we'll need to wait until ATO is in place.

A stock will be gradually phased out this year.
Hopefully all S stock will be in place by the end of this year.
There will be no improvement in acceleration or braking when the A stock has gone.
There will be no improvement in acceleration or braking until the Power Upgrade and the new Signalling System is completed by 2016.

It's not all that slow to be honest - it's cautious, as the manafacturer has learnt from past mistakes on the proper railway that introducing these new technologies can be troublesome and handing them over instantly and expecting them to work out the box is just unrealisitc. Every fault that occurs in London is rectified on all the units under construction in Derby, won't exist on units yet to be built and will be fixed on the trains already in service as and when the maintenance schedule allows. The more reliable the train becomes the faster we'll see deliveries occuring. Don't forget we're at the delicate stage where neasden can't take many more S Stocks without scrapping A Stocks first - It is my understanding that LU aren't quite ready to let go of the safety net they provide just yet - but such a time will be soon and we shall then see a significant increase in the frequency of deliveries from oop norf.

As for S8 Performance - the capping is independant of the fact A Stock are operating on the line. The signalling is designed for a train with A Stock performance. A train that exceeds that performance exceeds the safe operating window for the signalling. Upgrating the S8s once all the As are gone would be unsafe, as they would then be beyond that window. Why on earth would LU want to compromise safety in such a blatant and pointless manner.

It's the same with the 09TS on the Vic, the 96TS (in stages) on the Jubilee, the 92TS on the Central. We will ultimately see an increased performance S Stock, but the signalling upgrade has to come first.

Ensuring that people don't overheat to the point of fainting is beyond the scope of comfort. Sticking your head in an oven is very uncomfortable if its on, but no-one would say it becomes comfortable once switched off either

I'm pretty sure the power will be turned up to 750v when the A stock has gone. The S stock is a very power hungry train and with all of them running on the line at the same time there are bound to be problems at 630v.

your probably saying the truth and when i said that it sees a long time till the S stock is allowed to run faster i should have thought of how long has taken and is taking for the 96 and 95ts to go ATO