Are Top Speeds Really Just the Recommended Speed?

[Islineclear3_1]

I believe most of the slam-door Mk1 third-rail units bar the "Greyhounds" and 4REPs balanced at about 88 mph on level track.

When a many of these units were introduced in the '50s and '60s the Southern Region 'officially' had an 85mph ceiling anyway.

Maybe officially, but I remember seeing lineside "90" signs enabling 90mph running and on the straight between Tonbridge and Ashford, doing the "ton" wasn't unheard of in a Cep

 

[hexagon789]

Maybe officially, but I remember seeing lineside "90" signs enabling 90mph running and on the straight between Tonbridge and Ashford, doing the "ton" wasn't unheard of in a Cep

Presumably it changed at some point. Certainly 90 was permitted on the Bournemouth line by 1967.

 

[30907]

Presumably it changed at some point. Certainly 90 was permitted on the Bournemouth line by 1967.

The SR limit for hauled stock was 85, but MU stock was 75 until IIRC Kent Coast stage 2 was completed in 1962, when the 90 limit was introduced.

 

[hexagon789]

The SR limit for hauled stock was 85, but MU stock was 75 until IIRC Kent Coast stage 2 was completed in 1962, when the 90 limit was introduced.

Interesting, I would've thought that the EMUs would've also been allowed 85 where permitted what with their faster-acting EP brakes.

 

[Railperf]

Wasn't the class 350 uplift due to a modification by Siemens to allow greater motor spinning speeds so would have been design approved before release on service duties?

There were a number of modifications required as far as I recall ... https://www.railwaygazette.com/news...leet-upgraded-for-higher-speed-operation.html

 

[Jozhua]

Speaking of going over rated speeds, say a class 158 super sprinter (with a limit of 90mph) was pulling a class 156 (with a limit of 75mph) on a downhill section, such as in the South Transpennine from Manchester to Sheffield, could the whole train go up to 90 or would it have to remain at 75mph?

 

[Shaw S Hunter]

Speaking of going over rated speeds, say a class 158 super sprinter (with a limit of 90mph) was pulling a class 156 (with a limit of 75mph) on a downhill section, such as in the South Transpennine from Manchester to Sheffield, could the whole train go up to 90 or would it have to remain at 75mph?

Lower limit always applies. More interesting is something like a reasonably solid riding 156 (75mph limit) leading a rather more nervous riding 142 (also 75mph limit): it's not unusual in certain locations for such a combination to exceed 80mph with the driver not noticing if not checking the speedo. Meanwhile the guard in the rear of the 142 is only too well aware of the speed!

 

[Jozhua]

Lower limit always applies. More interesting is something like a reasonably solid riding 156 (75mph limit) leading a rather more nervous riding 142 (also 75mph limit): it's not unusual in certain locations for such a combination to exceed 80mph with the driver not noticing if not checking the speedo. Meanwhile the guard in the rear of the 142 is only too well aware of the speed!

Strange the 156 has the same limit as a Pacer! Makes me wonder whether it's worth rating slower trains to be able to work at higher speeds, especially if they are needed to work alongside faster units?

 

[Shaw S Hunter]

Strange the 156 has the same limit as a Pacer! Makes me wonder whether it's worth rating slower trains to be able to work at higher speeds, especially if they are needed to work alongside faster units?

The longer vehicled types might be ok, questionable for 150s and no chance for Pacers.

 

[Jozhua]

The longer vehicled types might be ok, questionable for 150s and no chance for Pacers.

Yeah definitely not a chance for pacers, even doing 75mph in one of those things is an experience! It's like riding a bus mounted on a freight car or something!

 

[Richard Scott]

Presumably it changed at some point. Certainly 90 was permitted on the Bournemouth line by 1967.

Remember having 73110 with a 3-Rep plus 8TC between Southampton and Bournemouth in 1988 on a very wedged train meaning we were stood next to one of the TC cabs. The speedo hit 100mph and someone near a window timed it to 103mph (allowing a bit for error would expect it was a comfortable 100mph).

 

[driver_m]

TPWS overspeed grids are only fitted in advance of some severe reductions in permissible speed. Though Virgin's Super Voyagers have TASS which I think would prevent such an overspeed.

I am slightly surprised that Voyagers don't have a speed limiter fitted like HSTs and some DMUs such as 170s.

Only just noticed this thread. But yes, the TASS does prevent overspeeding on our 221's in exactly the same way as on a Pendo . The maain difference being that a pendo will let you release the brakes when it has intervened and the required speed drop has been achieved , a voyager won't and will bring the train to a stop following an intervention.

 

[AJM580]

Speaking of going over rated speeds, say a class 158 super sprinter (with a limit of 90mph) was pulling a class 156 (with a limit of 75mph) on a downhill section, such as in the South Transpennine from Manchester to Sheffield, could the whole train go up to 90 or would it have to remain at 75mph?

Mostly they would stick to 75 mph. But in my experience,156s were quite capable of 80 mph + and I have records of a 156/158 combo doing 86 mph on the downhill section from Hethersett to Trowse.

 

[Eccles1983]

A 142 has been dragged at 90mph for a long distance on the WCML inadvertently behind a 158.

Would of been some ride .....

 

[Metal_gee_man]

At least it happened on the WCML, imagine that happening over a curvy or pretty knackered bit of track with dips and camber changes, theoretically the WCML was engineered to such a standard so that 125mph was comfortable and 140mph was achievable (if they'd allowed it without in cab signals)

 

[atraindriver]

<deleted>

 

[theageofthetra]

Maybe officially, but I remember seeing lineside "90" signs enabling 90mph running and on the straight between Tonbridge and Ashford, doing the "ton" wasn't unheard of in a Cep

A REP did an alleged 115mph with a contingent of no doubt bowel loosened French engineers when testing if 3rd rail could cope with Eurostar stock and current drain. A night possession between Tonbridge and Headcorn and a 'Kojak with a Kodak' speed gun.

 

[hexagon789]

Remember having 73110 with a 3-Rep plus 8TC between Southampton and Bournemouth in 1988 on a very wedged train meaning we were stood next to one of the TC cabs. The speedo hit 100mph and someone near a window timed it to 103mph (allowing a bit for error would expect it was a comfortable 100mph).

I've definitely read that 4REPs were capable of far more than 90, definitely at least 100.

Only just noticed this thread. But yes, the TASS does prevent overspeeding on our 221's in exactly the same way as on a Pendo . The maain difference being that a pendo will let you release the brakes when it has intervened and the required speed drop has been achieved , a voyager won't and will bring the train to a stop following an intervention.

Is that on any overspeed or simply going over the maximum for the unit?

 

[Llama]

Any overspeed where TASS is in operation, as well as the unit maximum speed irrespective of TASS, I suspect.

 

[hexagon789]

Any overspeed where TASS is in operation, as well as the unit maximum speed irrespective of TASS, I suspect.

That must be quite a pain if you allow the unit to just slip over the limit, because you don't get much leeway with TASS compared to ATP IIRC.

 

[cjmillsnun]

If that were the case, wouldn't a few examples have been converted for when deputising for 91s by now?

No as there would be a shedload if paperwork to complete.

 

[Highlandspring]

I know of a 150 being dragged at a ton by a 158, back in the day.

Doubt many 158s would even get to a ton on their own nowadays, let alone dragging a 150!

I've seen a photo of a 158 speedo showing just I've 100 (in an intermediate cab being dragged by a 170). 90mph+ for a 158/150 combo wasn't unheard of when the 158s were new to Scotland.

 

[hexagon789]

I've seen a photo of a 158 speedo showing just I've 100 (in an intermediate cab being dragged by a 170). 90mph+ for a 158/150 combo wasn't unheard of when the 158s were new to Scotland.

On the record breaking Edinburgh & Glasgow run with two 158s in the 1990s (I forget the precise year), the units ran most of the line at 100 or over and recorded a maximum of 107.

 

[PudseyBearHST]

Any overspeed where TASS is in operation.

Correct.

That must be quite a pain if you allow the unit to just slip over the limit, because you don't get much leeway with TASS compared to ATP IIRC.

You get a few mph leahway but some units are more sensitive than others. The unit I was on yesterday had TASS going off even though speedometer was showing exactly 125 (line speed 125) which is annoying.
Also, if you lose tilt, you have to get the brakes in quickly and heavy otherwise TASS will go off.

 

[hexagon789]

Correct.



You get a few mph leahway but some units are more sensitive than others. The unit I was on yesterday had TASS going off even though speedometer was showing exactly 125 (line speed 125) which is annoying.
Also, if you lose tilt, you have to get the brakes in quickly and heavy otherwise TASS will go off.

I think I read in a previous thread that TASS gives 1.5mph before giving a warning, 3mph before an intervention brake application. ATP is 3 and 6mph respectively I believe. So TASS gives less of an allowance, unless I've remembered the figures wrongly.

Must be 'fun' when that happens, do drivers routinely drive slightly under the limit to allow for this?

 

[Jozhua]

Do the automatic braking systems activate when the train goes over it's "Maximum Speed" or just line speed?

So for example, would a 158 be able to do 100 in a 125 zone without a problem?

 

[hexagon789]

Do the automatic braking systems activate when the train goes over it's "Maximum Speed" or just line speed?

So for example, would a 158 be able to do 100 in a 125 zone without a problem?

Unless there is TPWS fitted in the vicinity (such as approaching a significant speed restriction), I don't believe there is anything to physically prevent a 158 from doing 100mph like that, no.

Not all trains have either speed limiters, nor systems to prevent such overspeeds.

 

[BMIFlyer]

On Siemens units there is a failsafe - on the 185 IIRC it is 103mph.

Unless there is TPWS fitted in the vicinity (such as approaching a significant speed restriction), I don't believe there is anything to physically prevent a 158 from doing 100mph like that, no.

Not all trains have either speed limiters, nor systems to prevent such overspeeds.

 

[hexagon789]

On Siemens units there is a failsafe - on the 185 IIRC it is 103mph.

170s also have an overspeed device which cuts power if speed rises above 103mph. Power then cannot be reapplied until speed drops below 97mph. Class 68s have a similar device but with slightly different cut-out speeds.

However, I don't believe any 158s have such a device.

 

[PudseyBearHST]

I think I read in a previous thread that TASS gives 1.5mph before giving a warning, 3mph before an intervention brake application. ATP is 3 and 6mph respectively I believe. So TASS gives less of an allowance, unless I've remembered the figures wrongly.

Must be 'fun' when that happens, do drivers routinely drive slightly under the limit to allow for this?

I believe in a 390 it is 3.5mph above you get a TASS warning and 6mph above you get an intervention. I think 221 is 4.5mph and 5.5mph respectively. I need to double check this though.

Not really to be honest unless you know the unit is particularly sensitive. Losing tilt is what you can call ‘fun’ for the passengers and catering crew especially on a few units that keep losing and gaining tilt every few minutes which causes a sudden and heavy brake application as speed needs to be reduced by 25 mph quickly before TASS starts screaming at you.