Possibly detected as an extra wheel by axle counter sensors resulting in a miscount? I wonder if DB have any problems with this as MTB and axle counters are widely used.
That's a very good point, especially with ancient stock. I expect the most modern bogie designs will be suitable as at least in outline they tend to be designed generically for international markets, some of which routinely specify the tech.
There is plenty of equipment available, that does not cause any issues. But it has to be installed.
Unfortunately not. Since weight plays a decisive role, even modern designs cannot always accommodate a magnetic track brake. Even similar bogies can differ depending on the specification.
Precisely my point.
We're talking about DMUs with barely enough power as it is - the units you describe are tram trains, where that technology is more normal.
Retro-fits of all kinds are difficult in many respects. Clearly much better if you can design the feature into a new train... like the massive near total fleet replacement taking place in Wales currently.
An interesting read. The train did not slide though, the WSP did it‘s thing. In fact the rate of brake retardation reduced as the brake was moved from step two to emergency. Very similar to other incidents. Could it be a rather primitive WSP not being able to keep the wheels in a controlled slide prolonged the braking distance unnecessarily?
Of course the train slid, the coefficient of friction wasn't able to support the brake demand and the wheels were going round more slowly than the train was travelling forward. Just because they weren't locked doesn't mean they weren't sliding.
I know MTBs are common on light rail derived vehicles. I do not advocate retrofitting the cl.158s. These will be gone (from Wales at least) fairly soon, but consideration might be given to MTB provision on replacement new trains. Power consumption is not large (can't find any figures currently) and is only for a short period when deployed, but a suitable supply is required.
Which requires a material electricity supply. And the replacements for the class 158s will also be mechanical rather than electrical, hence my doubts about the applicability of the technology.
and
This is going to depend on the exact details of the WSP algorithm and hardware. As mentioned by @millemille more modern systems have better algorithms and the DB425 with the modified algorithm might have been more effective than the one at Stonegate.
It’s a what if but the Salisbury report has a fairly good infographic showing stopping distances with different types of sanders, including no sand.
3 weeks is a bit late for that.
Isn't the loop at the summit? I.e. trains don't descend into the loop, they are ascending from both directions.
Its possible that investigations have unearthed new technical factors (e.g. the performance of a component) not previously identified, needing fleet-wide checks.
The most important point with the ET425 was not even the optimization of the software in general, but the prevention of dangerous freakouts of the WSP software. Improved braking performance in general was just a bonus.
With an EMU, the dynamic brake can be used to control the WSP very quickly and accurately.
Yes it’s possible, but we’re talking about an identified on day 1 problem that saw all of TFW’s units go through checks within days.
probably am, my mistake sorry.
Variable rate may not make a difference, but surely more sanders (and so more sand pipes) gives the train as a whole redundancy - better to have two out of four sand pipes work than zero out of two. I assume the left and right pipes commonly share a single sander / sand supply.
Some rolling stock have been modified so that all units in a formation sand at the same time thereby giving redundancy and is almost equivalent if a double rate sander in those cases.
Which isn't a lot of use for a single unit like this. Remember of course that TfW are famous for the number of two-car formations running around in spite of loadings.
Just thinking that "defensive driving" policies may actually make this worse. If the driver only ever uses light braking then they may not be aware that adhesion is poor or the sanders are faulty, until it gets bad enough that their gentle braking doesn't work and then the higher notches don't work either. I'm actually inclined to think that drivers should user higher braking notches when approaching a station (except when there's also a red signal) and the occasional station overrun should be tolerated. This might also reinforce the importance of signal stops by encouraging drivers to treat them differently from other stops.
In my experience, no difference. A train cannot enter passenger service from any location with a known sander defect and has to come out of service if the driver becomes aware of a sander defect.
If they break a bit harder for a station, but still reasonably early when adhesion is suspected to be poor, then they will find out whether there is enough adhesion to sustain a heavy brake application and if there isn't they can probably still stop on a lighter one (assuming adhesion is gradually deteriorating). If they don't hen they've only overrun a station, more of an operating inconvenience than a safety issue.
Is a very good question and one I'm sure RAIB and others are looking at as we speak...
It had also worked a full day's diagram. In October, I'd suggest that inspection at the start of day may not be the key issue.
