Speed limits

[AM9]

A Japanese car; with a CVT gearbox. Ouch. That sounds like an (automotive) fate worse than death.

I didn't say that it was Japanese.

 

[hexagon789]

But apart from checking the logs, is there no system to prevent speeding?

ATP/ERTMS where provided will, plus TPWS on the approach to some (but not all) heavy reductions in speed limits.

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.

Probably not needed very much, there's not an awful lot of continous high speed running, most Welsh mainline have relatively sawtooth speed profiles. It's not like the GWML or ECML where you have near 30 mile long sections of continuously permitted 125mph running.

No, this is not the case. The 80x ASL can be set at any speed or none. The only exception is when an 801 unit is running in diesel/limited traction mode. In this instance the ASL will not operate.

My mistake, I've obviously misread whatever it was I read on the subject. I can't find it now anyway in searches.

I strongly suspect we exceeded the speed limit to do this when we were on the LGV

The TVM imposes a strict 15km/h overspeed, so I'm not sure how that could've happened unless it was disabled (whether that's permitted is another matter). We've had similar discussions previously with late running ICE trains in Germany though...

 

[Highlandspring]

Some Hot Axle detectors have speed equipment built into them which can show the speed of passing trains in the signal box.

All HABD and Gotcha/Wheelchex equipment records train speeds.

Speed guns are very rare these days but can still be used.

ScotRail still use them a lot for some reason.

 

[choochoochoo]

But apart from checking the logs, is there no system to prevent speeding?

Apparently the 313 was limited to 30mph in DC mode whilst on the Northern City Line section. Not that I ever tested it out.

I believe it cut out the traction motors but wouldn't stop you exceeding the speed should you be coasting downhill.

 

[edwin_m]

The TVM imposes a strict 15km/h overspeed, so I'm not sure how that could've happened unless it was disabled (whether that's permitted is another matter). We've had similar discussions previously with late running ICE trains in Germany though...

With no lineside signals on LGVs the TVM can't be disabled totally in passenger service. Speed supervision can clearly be disabled sometime for test purposes, witness the serious accident on LGV Est during commissioning tests. I believe SNCF schedules trains at less than maximum speed to give some reserve for recovery of delays.

 

[norbitonflyer]

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.

On the cars I've had with it (Ford, Vauxhall, Citroen), you can still brake with cruise control - a touch of the brake (or clutch) pedal is enough to cancel it. However, a speed limiter remains set if you slow down.

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.

I did that to my son - we stopped to swap drivers and, as I didn't switch off, the limiter remained set. (It was set to 72 anyway). He also thought we had a puncture because the lane departure warning system was on (it makes the steering slightly heavier if you stray towards the white lines)

 

[O L Leigh]

All HABD and Gotcha/Wheelchex equipment records train speeds.

As does Panchex.

 

[AM9]

On the cars I've had with it (Ford, Vauxhall, Citroen), you can still brake with cruise control - a touch of the brake (or clutch) pedal is enough to cancel it. However, a speed limiter remains set if you slow down.


I did that to my son - we stopped to swap drivers and, as I didn't switch off, the limiter remained set. (It was set to 72 anyway). He also thought we had a puncture because the lane departure warning system was on (it makes the steering slightly heavier if you stray towards the white lines)

My last car had a speed limiter that would do just that, - it acted as though the engine had a govenor fitted (that limited in every gear) and that limit stayed on as long as the engine was running or until it was manually cancelled. The cruise function would cancel whenever the braking was activated, - including when the stability system blipped one or more of the wheels. When re-engaged, it retained the set speed unless the engine had been stopped.

 

[Inversnecky]

My Vauxhall has a speed limiter adjacent to the cruise control, if you wish to use it.

 

[O L Leigh]

Bringing it back on-topic...

Speed set was on the EMUs I used to sign but was not permitted to be used and/or deactivated (depending on who you asked).

Ditto.

We were not permitted to use it because I believe that it's (mis)use was implicated in the causes of a SPAD that happened on a different TOC using similar units. There was also the issue that if you touched the brakes it would switch itself off, so there was a risk that a driver would have it set to the linespeed, have to brake for a cautionary aspect related to a crossing and then open the taps at the next green believing that the speed-set would still be active and prevent overspeeding.

 

[hexagon789]

With no lineside signals on LGVs the TVM can't be disabled totally in passenger service. Speed supervision can clearly be disabled sometime for test purposes, witness the serious accident on LGV Est during commissioning tests. I believe SNCF schedules trains at less than maximum speed to give some reserve for recovery of delays.

That would make more sense, I didn't see them permitting the speed monitoring to be disabled somehow

 

[Watershed]

The timing rules used for timetables do not assume everything will go perfectly, they have slack built in.

Yes and no - SRTs are rounded up to the nearest half-minute, and there are engineering and performance allowances to ensure that TSRs/ESRs and the imperfection of daily operations don't cause a cascade of delays. But these are usually only a few minutes at a time - you wouldn't recover a big delay in most cases.

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?

There are many factors, just one of which will have been ensuring a 3 minute headway with the 3 aspect signalling that is predominantly in use on the Chiltern line.

A sudden increase in linespeed means that the braking distance is also suddenly much greater, and thus the next signal might need to be a mile away where the previous signals were half a mile apart.

Any change in speed will create a localised increase in headway, but a big change creates a big increase that may then become the limiting factor on the route.

As I say, it just takes one small thing to give rise to the limiting factor for speed limits. I'm sure they increased the limits as much as was economically viable as part of the Evergreen phases.

 

[387star]

It's often complete guess work and certainly adds to the difficulty of learning routes with different train formations

Some low speeds are baffling. 20mph on perfectly straight track but there must be a reason for it.

 

[43066]

I didn't say that it was Japanese.

Touché. I made an assumption there.

We were not permitted to use it because I believe that it's (mis)use was implicated in the causes of a SPAD that happened on a different TOC using similar units. There was also the issue that if you touched the brakes it would switch itself off, so there was a risk that a driver would have it set to the linespeed, have to brake for a cautionary aspect related to a crossing and then open the taps at the next green believing that the speed-set would still be active and prevent overspeeding.

Ditto not allowed to use “low speed control” into sidings/through the wash road.

Rightly so, in my view. If you can’t control the speed of your train, whether at 125mph, or 3mph, you’ve got absolutely no business being in the driver grade.

 

[dk1]

On 755s the tortoise (or is it a turtle) mode is selected which closes all vents on the power pack and limits the train speed to 3mph. The new wash plant at Crown Point also displays the exact speed on a line side display as it passes through.

 

[hexagon789]

On 755s the tortoise (or is it a turtle) mode is selected which closes all vents on the power pack and limits the train speed to 3mph. The new wash plant at Crown Point also displays the exact speed on a line side display as it passes through.

Do you have to coast through or can the engines run for a short period with the vents closed?

 

[dk1]

Do you have to coast through or can the engines run for a short period with the vents closed?

The engines continue as normal as it’s not long enough to cause any to overheat. Under normal circumstances we can also pass through in electric mode.

 

[gimmea50anyday]

in the old days where speeds 10 mph over limit were not un common, seen logs of Deltics doing 110mph plus, HST’s doing 135mph and 91’s doing 135-138mph, I have done 135mph plus on 91’s in the 90’s.

I used to read 132-133mph on the shop TMS on VXC voyagers between Didcot and Reading on evening services when they were first introduced. Old Oak drivers wanting to get home! As much as people mock them they were certainly far smoother at 130 than 80x units are today at 110!

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.

I think, I may be mis-remembering bits

124mph is 200kmh, but 125mph is 201kmh (and totally buggering up anyone’s OCD in the process! XD)
In the rear cab I see 124 displayed on the speed meter on the TMS. If the train is holding the service speed at 200kmh then that would make sense as far as any cruise control/speed set/speed limiter is concerned as the computers will be working logically (no pun intended) in metric.

 

[The Planner]

Yes and no - SRTs are rounded up to the nearest half-minute, and there are engineering and performance allowances to ensure that TSRs/ESRs and the imperfection of daily operations don't cause a cascade of delays. But these are usually only a few minutes at a time - you wouldn't recover a big delay in most cases.


There are many factors, just one of which will have been ensuring a 3 minute headway with the 3 aspect signalling that is predominantly in use on the Chiltern line.

A sudden increase in linespeed means that the braking distance is also suddenly much greater, and thus the next signal might need to be a mile away where the previous signals were half a mile apart.

Any change in speed will create a localised increase in headway, but a big change creates a big increase that may then become the limiting factor on the route.

As I say, it just takes one small thing to give rise to the limiting factor for speed limits. I'm sure they increased the limits as much as was economically viable as part of the Evergreen phases.

SRTs are rounded down too. Evergreen was only targeting 100mph as that was all the stock could do. It should have spent the money used on bi-di on extra normal signaling north of Risborough as its a bit of a mess and even worse north of Bicester.

 

[ExRes]

On the juvenile side, one bit of fun was to set the speed limiter on a 90 to zero and see if the driver trying to take it out of the holding sidings cottoned on or reported it as a failure, the reverse of that of course, was the idiot who would leave it set on max

 

[Felixkoch2312]

Speeding is carefully not permitted, except if in firmly controlled test conditions, with pertinent notification presented on all material staff ahead of time.

That doesn't stop it occurring, mind. There have been some fascinating paces done by class 80x on the ECML as of late.

 

[philthetube]

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?

This limit will be to increase line capacity until the line splits at Neasden.

Also there is no logical advantage to having higher speeds out of a terminus than entering as there is no need for higher capacity, though in reality it is useful for recovery

 

[hexagon789]

The engines continue as normal as it’s not long enough to cause any to overheat. Under normal circumstances we can also pass through in electric mode.

Thanks. The wash road has OLE then?

124mph is 200kmh, but 125mph is 201kmh (and totally buggering up anyone’s OCD in the process! XD)
In the rear cab I see 124 displayed on the speed meter on the TMS. If the train is holding the service speed at 200kmh then that would make sense as far as any cruise control/speed set/speed limiter is concerned as the computers will be working logically (no pun intended) in metric.

Yes, afaik it works in km/h so it makes 125mph, a round 200km/h which is of course actually 124mph hence the discrepancy.

I used to read 132-133mph on the shop TMS on VXC voyagers between Didcot and Reading on evening services when they were first introduced. Old Oak drivers wanting to get home! As much as people mock them they were certainly far smoother at 130 than 80x units are today at 110!

I've seen a few logs with such speeds in the early days, but none of 390s doing anymore than 128. Presumably because 390s simply can't because of TASS on all sections of route they run on at 125mph.

 

[dk1]

Thanks. The wash road has OLE then?

Certainly has. The 745s have to go through like the 90/DVTs did before them.

 

[hexagon789]

Certainly has. The 745s have to go through like the 90/DVTs did before them.

Sorry, I think I worded that poorly to what I actually meant. I should've said live OLE, never mind.

 

[Bald Rick]

I've seen a few logs with such speeds in the early days, but none of 390s doing anymore than 128. Presumably because 390s simply can't because of TASS on all sections of route they run on at 125mph.

Yes the TASS will stop them going over.

 

[dk1]

Sorry, I think I worded that poorly to what I actually meant. I should've said live OLE, never mind.

Oh I get what you meant now. Yes it’s not a problem being live.

 

[JonasB]

ATP/ERTMS where provided will, plus TPWS on the approach to some (but not all) heavy reductions in speed limits.

How common is ATP or ERTMS? Are there many lines without it?

 

[hexagon789]

Yes the TASS will stop them going over.

Is it 126.5 or higher that it intervenes are?

Oh I get what you meant now. Yes it’s not a problem being live.

Yes, that's what I meant even of it wasn't quite what I typed!

How common is ATP or ERTMS? Are there many lines without it?

In the UK? Almost all of them.

I believe ERTMS is just on the Cambrian as a long-term trial. ATP is on the GWML (including Heathrow branch) and the Chiltern Mainline. Both different incompatible systems.

 

[Bald Rick]

How common is ATP or ERTMS? Are there many lines without it?

ETCS is only on the Cambrian line, the Thameslink core (although not mandatory use on the latter), and the Heathrow branch. It will be appearing on the Moorgate branch next year, and then start appearing more widely.