hexagon789
Veteran Member
As evidenced by the 802s...In many cases they don’t, even on types far newer than the HST. It’s down to the driver to avoid exceeding max line speed, just as with any other speed limit.
As evidenced by the 802s...In many cases they don’t, even on types far newer than the HST. It’s down to the driver to avoid exceeding max line speed, just as with any other speed limit.
In many cases they don’t, even on types far newer than the HST. It’s down to the driver to avoid exceeding max line speed, just as with any other speed limit.
I’ve certainly never driven a car with a 70mph speed limiter.
Ah, like a speed-set. The 90s and 91s have one, don't know if any others doSorry I didn’t specify. Some cars have a thing where you can set a certain speed and when you reach that speed the power will cut off regardless of how much throttle you are giving. A bit like cruise control but you still accelerate and brake like normal.
Been common for many years. Class 90s/DVTs had ASL in 1987 and class 170s had limiters kicking in at 102mph from the late 90s.I’m sure there’s an extremely simple answer to this question but why are trains even capable of exceeding the maximum speed they will encounter in the UK? Why doesn’t an HST just cut power at 125mph like the speed limiter in a car?
Ah, like a speed-set. The 90s and 91s have one, don't know if any others do
Am I right in thinking they're 200km/h or off? Whereas the 90s and 91s are variable in 5m/h increments.The Hitachi units have speed set.
Needs to be set, of course...
Sorry I didn’t specify. Some cars have a thing where you can set a certain speed and when you reach that speed the power will cut off regardless of how much throttle you are giving. A bit like cruise control but you still accelerate and brake like normal.
Ah, like a speed-set. The 90s and 91s have one, don't know if any others do
Am I right in thinking they're 200km/h or off? Whereas the 90s and 91s are variable in 5m/h increments.
And the 89, the unique 87101, 175s, 180s, 185s, 390s and a few moreAh, like a speed-set. The 90s and 91s have one, don't know if any others do
I did read something about the 80x ASL, something like it only works at 60mph or above and works in km/h so the maximum it will allow is 124mph.Am I right in thinking they're 200km/h or off? Whereas the 90s and 91s are variable in 5m/h increments.
it's fun when you activate it un-knowingly, my sister has done that twice and once was in a loan car, she got a bit worried when it would not accelerate past a really low speed (~15Mph?), disabled it an all was well.Ah yes, I know what you mean. I’ve driven cars with that, I’ve just never used it .
But apart from checking the logs, is there no system to prevent speeding?Historically it did happen, not that infrequently, nowadays only by accident really (the TPE 802 doing over 140mph a wee while back being a case in point).
They do download the OTDR logs from time-to-time to check.
Though as far as I know it's long since disabled on the 175s - judging by the state of some of the buttons I'm not sure they've ever worked.And the 89, the unique 87101, 175s, 180s, 185s, 390s and a few more
Not sure, but don’t think so - as the RAIB report into the Neville Hill collision implies it could have been used there, at a speed clearly less than 125mph. (Ironically, see the avatar of @43066 for the result!)
My last car had a cruise/limiter which could be set to any speed between 20mph and 75mph. It had a CVT gearbox as well so it could reduce the (virtual) gear to provide engine braking if necessary.In many cases they don’t, even on types far newer than the HST. It’s down to the driver to avoid exceeding max line speed, just as with any other speed limit.
I’ve certainly never driven a car with a 70mph speed limiter.
On some traction yes, on others no.But apart from checking the logs, is there no system to prevent speeding?
My last car had a cruise/limiter which could be set to any speed between 20mph and 75mph. It had a CVT gearbox as well so it could reduce the (virtual) gear to provide engine braking if necessary.
The timing rules used for timetables do not assume everything will go perfectly, they have slack built in.How come delays can sometimes be "made up", if speeding isn't allowed and drivers are expected to go at line speed?
I think you’re misunderstanding what the purpose of the RAIB is. It’s remit is to investigate, report and recommend. It isn’t there to take enforcement action, that is down to others, notably the ORR.Here is where I tend to find the RAIB a little toothless. A TOC may have the capability to implement use of a speed limiter to prevent a Neville Hill style collision but can freely refuse to do so. My TOC doesn't allow the use of Speed Set.
id read something about the 80x ASL, something like it only works at 60mph or above and works in km/h so the maximum it will allow is 124mph.
I think, I may be mis-remembering bits
Most timetables are based on sectional running times, which are based on recorded data. This usually will be assigned to rolling stock which is either similar or the same as what usually works the route. Note, if a train loses time due to performance differentials (e.g. a 150 on a 158 diagram) then this would be considered a fleet delay rather than a timetabling problem.How come delays can sometimes be "made up", if speeding isn't allowed and drivers are expected to go at line speed?
How is a train’s speed recorded/monitored to ensure a driver isn’t speeding? I remember seeing an old episode of The Tube where a Driver Manager was standing on a platform with a speed gun. Does that still happen? Are there cameras like on roads?
Speed guns are very rare these days but can still be used.How is a train’s speed recorded/monitored to ensure a driver isn’t speeding? I remember seeing an old episode of The Tube where a Driver Manager was standing on a platform with a speed gun. Does that still happen? Are there cameras like on roads?
How are speed limits decided?
For example, leaving Marylebone - once out of the tunnels the line is straight but the speed limit is less than 100 until the line reaches Wembley. Why can't it be 100 sooner?
The timing rules used for timetables do not assume everything will go perfectly, they have slack built in.
Also many timetables are scheduled based on slower rolling stock than that which normally operates the line. While the top speed may not be any higher due to linespeed restrictions a modern EMU like a 331 running on timings intended for an older EMU like a 319 can make up a lot of time due to faster acceleration.
Also if things aren't too busy station stops can often be completed in less time than scheduled.
Also bear in mind running times are based on ½ minutes and therefore rounded, it shouldn't make much difference end to end, but some roundings will allow time to be caught up.Most timetables are based on sectional running times, which are based on recorded data. This usually will be assigned to rolling stock which is either similar or the same as what usually works the route. Note, if a train loses time due to performance differentials (e.g. a 150 on a 158 diagram) then this would be considered a fleet delay rather than a timetabling problem.
Added into the timetables are engineering allowances to cover speed restrictions imposed, pathing allowances to allow trains to change routes for example, or running against expected restricted aspects and performance allowances which are agreed as a measure to protect against services persistently losing time in a section. TOCs usually are reluctant to include the latter as this will negatively impacts the business.
So, if a train loses time in a section and it has 1.5 mins performance allowance, it may catch that time up. It is more difficult to catch up with engineering and pathing allowances. Not impossible but more difficult.
A signalman can also proactively path a train to allow it to catch up time and prevent a PPM failure. This will usually be agreed as part of a regulation policy. It may mean holding other services to let a train catch up to its schedule and prevent it being regulated for trains which are on time.
I hope this gives an overview of how delays can be caught up. Unfortunately, the railway is very tightly pathed and trains run very close together, it can be extremely challenging to catch up time.
I was on a TGV in France a number of years ago. We left the regional station I was travelling from 1h45 late but arrived into Paris only 45 late. I strongly suspect we exceeded the speed limit to do this when we were on the LGV as there would have been very little traffic ahead of us, but it was a very long time ago and I have no evidence we did as smart phones weren't a thing then.