Exceeding maximum line speed on LNER

[Tallguy]

I know the max speed on the London (KGX) to Newcastle route is 125mph on LNER with their very nice Azuma Trains.

Is it technically possible for the driver to accelerate the train beyond 125mph should he or she want to, or is there some form of speed limiter device on the trains so when the specified max speed is reached, the train will not accelerate further and will only hold the speed, regardless of human input?

 

[JonathanH]

A speed limiter applies at 124.89mph.

RIP Great western 125mph.... (IETs to have speed limiter automatically set)

As of next week all GWR IETs will have the speed limited set automatically to 125mph (in practice this keeps the train at 124mph due to the difference between mph and kph). So no more 125mph on the Western :-(

www.railforums.co.uk

 

[hexagon789]

I know the max speed on the London (KGX) to Newcastle route is 125mph on LNER with their very nice Azuma Trains.

Is it technically possible for the driver to accelerate the train beyond 125mph should he or she want to, or is there some form of speed limiter device on the trains so when the specified max speed is reached, the train will not accelerate further and will only hold the speed, regardless of human input?

The Azumas have the speedset (like cruise control on cars), hardwired to be both permanently on and unable to be set above 125mph.

In practice due to rounding the actual maximum as mentioned above is 123-123.5mph.

While the tolerance is 201km/h (the 124.89mph quoted above), the system works in whole mph. Ie 123.6 is 124mph, 123.4 would be 123mph.

Power dials off about 1mph before the set speed, so the balancing speed ends up being about 1-2mph below that set.

 

[Tallguy]

Thanks to both for your replies

 

[ComUtoR]

What if the unit was on a down gradient ? Would it accelerate past the limiter or would the brakes kick in ?

 

[driver9000]

What if the unit was on a down gradient ? Would it accelerate past the limiter or would the brakes kick in ?

In electric mode they should hold themselves back.

 

[hexagon789]

What if the unit was on a down gradient ? Would it accelerate past the limiter or would the brakes kick in ?

On electric the rheo brake should begin to kick in at about 124; on diesel mode I understand that the speedset doesn't do braking but will of course cut traction power.

 

[ComUtoR]

Cheers

 

[DanNCL]

The Azumas and associated fleets (IETs, 802s, 803s etc) are software limited to 124mph now but weren't when they were first introduced. There were a few overspeed incidents, one reaching as much as 148mph if I recall correctly, which is what led to the software change being implemented.

Many older fleets either have no speed limiting equipment at all or (as is the case with LNER's Mark 4 fleet) have a speedset that can be adjusted and enabled/disabled by the driver, effectively like cruise control in a car.

More generally overspeeding is protected against in key locations by TPWS but it's far from a perfect system and it isn't fitted everywhere.

 

[Juniper Driver]

What if the unit was on a down gradient ? Would it accelerate past the limiter or would the brakes kick in ?

444s and 450s do that as well.
Shows driving (taking power) on the gauge but doesn't go over 100mph even downhill.So obviously governed by computer.

 

[43066]

There were a few overspeed incidents, one reaching as much as 148mph if I recall correctly, which is what led to the software change being implemented.

If it was on diesel that would mean the HST has technically been dethroned as the “world’s fastest diesel train”.

Perhaps not a record the industry wants to shout about on this occasion, though….

 

[zwk500]

If it was on diesel that would mean the HST has technically been dethroned as the “world’s fastest diesel train”.

Perhaps not a record the industry wants to shout about on this occasion, though….

The old thread is here: https://www.railforums.co.uk/threads/a-tpe-class-802-got-up-to-145mph-a-record.211675/

 

[172007]

Class 172's limit to 100mph too.

 

[hexagon789]

If we are going on the line of trains with maximum speed limiters, as opposed to speedsets which cannot be set above the normal service maximum:

168/170/171 limit to a maximum 103mph
185s - same

In both cases I believe traction power cannot be reapplied until speed falls below 97mph and the TBC needs put to 'OFF' and then reopened before power can be obtained.


68s limit to 102 or 103, I forget which and power can't be restored until speed falls below 96mph IIRC.

 

[3RDGEN]

Did the 91/MKIV's get the overspeed lowered to 125ish or are they still 140+ limited?

 

[hexagon789]

Did the 91/MKIV's get the overspeed lowered to 125ish or are they still 140+ limited?

The speedset can be set as high as 150 and can still be set 'off' if desired.

 

[Pumbaa]

Class 172's limit to 100mph too.

How often do you get that out of them?

 

[D365]

In both cases I believe traction power cannot be reapplied until speed falls below 97mph and the TBC needs put to 'OFF' and then reopened before power can be obtained.

”Traction restrike” facility is commonplace on units with traction cut-off. Not sure whether or not it’s been a mandatory feature since the introduction of CTBC (combined traction-brake controllers).

 

[hexagon789]

”Traction restrike” facility is commonplace on units with traction cut-off. Not sure whether or not it’s been a mandatory feature since the introduction of CTBC (combined traction-brake controllers).

I don't think 165/166 have an overspeed limiter (so no 'traction restrike' either) and they have a CTBC.

Possibly it came in with 168s and onwards?

 

[thomalex]

I read somewhere that the ECML had been upgraded in preparation for 140mph on some sections but due to various reasons this wasn’t able to be operated.

Does anyone know what exactly is preventing this. I’m presuming if the tracks are in place, and the trains are capable of it, it would be power supply issues?

 

[DanNCL]

I read somewhere that the ECML had been upgraded in preparation for 140mph on some sections but due to various reasons this wasn’t able to be operated.

Does anyone know what exactly is preventing this. I’m presuming if the tracks are in place, and the trains are capable of it, it would be power supply issues?

Signalling. Conventional signalling can only be used for speeds up to 125mph. Anything above that requires cab signalling.

 

[LNW-GW Joint]

I read somewhere that the ECML had been upgraded in preparation for 140mph on some sections but due to various reasons this wasn’t able to be operated.
Does anyone know what exactly is preventing this. I’m presuming if the tracks are in place, and the trains are capable of it, it would be power supply issues?

Bald_Rick has the complete answer, but very little of the ECML is 140mph-ready.
That's track, signalling, OHLE, power supplies etc.
Once the ETCS conversion is commissioned (south of Peterborough), the signalling and trains will be ready.
But there's a lot to do to upgrade the track/formation and OHLE for regular 140mph, and such work is unfunded.
The power supply is being upgraded now, for the planned 125mph services, but whether it could cope with 140mph I don't know.
The amount of freight also comes into the equation (currently much less than on the WCML, but very little is electrically operated on either route).

 

[notadriver]

Bald_Rick has the complete answer, but very little of the ECKL is 140mph-ready.
That's track, signalling, OHLE, power supplies etc.
Once the ETCS conversion is commissioned (south of Peterborough), the signalling and trains will be ready.
But there's a lot to do to upgrade the track/formation and OHLE for regular 140mph, and such work is unfunded.
The power supply is being upgraded now, for the planned 125mph services, but whether it could cope with 140mph I don't know.
The amount of freight also comes into the equation (currently much less than on the WCML, but very little is electrically operated on either route).

I had a cab ride the other day - I think the overhead line equipment needs substantial upgrading if 140 mph were to be permitted. But I’d try to find a way to increase existing line speeds such as Stilton Fen and Newark and Doncaster - both of which are 100 mph. Imagine if some sort of spectacular tunnel was built avoiding york that could save 15 minutes too.

== Doublepost prevention - post automatically merged: 3 Jun 2023 ==

I don't think 165/166 have an overspeed limiter (so no 'traction restrike' either) and they have a CTBC.

Possibly it came in with 168s and onwards?

You don’t sign those tractions do you? Are your observations based on Train Simulator or similar ?

 

[zwk500]

I read somewhere that the ECML had been upgraded in preparation for 140mph on some sections but due to various reasons this wasn’t able to be operated.

Does anyone know what exactly is preventing this. I’m presuming if the tracks are in place, and the trains are capable of it, it would be power supply issues?

Signalling. Conventional signalling can only be used for speeds up to 125mph. Anything above that requires cab signalling.

And the track alignment, tolerance, cant, points, dynamic profiles clearance, OLE and some other bit's I'm sure I've forgotten. AIUI There was no serious upgrades for 140mph, even the flashing Green signalling was only installed on the sections used for testing around Stoke Bank north of Peterborough.

 

[D365]

Level crossings and platform edges.

 

[driverd]

168/170/171 limit to a maximum 103mph

Is this a Chiltern specific thing? I've never heard of this and I sign one of those traction (mind you, I've never tried this and don't think there's a 100mph stretch of track long enough to even threaten a 170 with getting to a ton, if it's even possible!).

On all the DMUs I sign (including some very new ones), there's no speed set, speed limiter or whatever traction restrike is - and a lot of them have CPBC.

 

[3RDGEN]

Is this a Chiltern specific thing? I've never heard of this and I sign one of those traction (mind you, I've never tried this and don't think there's a 100mph stretch of track long enough to even threaten a 170 with getting to a ton, if it's even possible!).

On all the DMUs I sign (including some very new ones), there's no speed set, speed limiter or whatever traction restrike is - and a lot of them have CPBC.

The Voith transmission on 175 flags overspeed at 103mph, guess it's the same on the other fleets using the same/similar transmission such as the 168/170/185's. 103mph is a bit tight if your on a falling gradient running at 100 anyway, I assume the power off/on requirement is to confirm the driver is still active.

 

[The Planner]

I had a cab ride the other day - I think the overhead line equipment needs substantial upgrading if 140 mph were to be permitted. But I’d try to find a way to increase existing line speeds such as Stilton Fen and Newark and Doncaster - both of which are 100 mph. Imagine if some sort of spectacular tunnel was built avoiding york that could save 15 minutes too.

Don't fall into the trap of thinking upgrading from 100 to 125 gets you loads of time, it doesn't. Its 7 seconds a mile ignoring acceleration and braking.

 

[Ken H]

Where does the speed input to the speed limiter come from?
A sensor on an axle which could be inaccurate due to tyre turning, or doppler radar? Or is there another new method I don't know about?
I dont think GPS would be accurate enough.

 

[apinnard]

Don't fall into the trap of thinking upgrading from 100 to 125 gets you loads of time, it doesn't. Its 7 seconds a mile ignoring acceleration and braking.

It was either going to be you or @Bald Rick