Differential Speed Restrictions
 

On the railways you often see differential temporary speed restriction signs like this one.
http://www.railsigns.co.uk/pics/pic_tsrwb2/pic_tsrwb2.html

The slower speed appears to apply mainly to freight trains but what actually determines which speed applies to which type of train?
Can anyone throw some light on the subject please?

Speed limits of specific steam engines
 

Slightly off topic but I would like to know why steam engines operating on the mainline have speed limits below that for the line, i.e RAH has a speed limit of 60mph on the main line yet Im sure that in steam days they ran at more than 60 mph. Even if the halls had a maximum speed of 60mph then surely Kings, Castles, Pacifics etc must have had top speeds in excess of 75 mph.

The top speed board (lower speed) applies to all trains, except passenger and empty coaching stock trains not conveying four-wheeled vehicles.

The lower speed board applies only to passenger and empty coaching stock trains not conveying four-wheeled vehicles.

Tony

Thanks Tony, I have already seen that information on the web but it doesn't appear to be as straightforward as it makes it sound.
From observations, questions that spring to mind are:
a) Why do freight trains with bogie wagons have to comply with the lower speed limit but passenger trains don't?
b) Why do light engines have to comply with the lower speed limit but loco-hauled passenger trains don't?

Freight trains have to comply with the top speed (slower) due to I presume weight. Light Diesels are not restricted to the slower speed.
The rule book states that a light engine can run at 75mph on a line where the line speed is 90mph or higher but is restricted to 60mph on a line where line speed is 85mph or lower I hope this clears up a bit of the confusion.

Les

Thanks Les. I assume the term "line speed" also apples to "temporary line speeds". If so that will explain why the light engines I have seen appear to be going noticeably slower than the passenger trains. I am not sure what the exact speeds are because the face of the TSR sign can't be seen from a public place.

Arn't permissible speeds set by braking distance? It is fairly well known that light engines and especaily steam engines take longer to stop than a whole train because most of the braking is done by the train.

So are air-braked passenger carriages better at stopping than air-braked freight stock?

I have seen a TSR (temporary speed restriction) of 30 over 70 this means that passanger trains and empty stock can run at 70 but freight runs over at 30 but a light engine can do 60.

Confused I know I am but its easier to understand when you work on it on a daily basis.

Les

Shed Cat you are actually straying off on a whole different ball game,
Its been awhile but here goes, Most pass trains run on the twin pipe system where most freight trains run on the single pipe system. By twin pipe I mean that the two rubber tubes (Bags) on the front and rear end of the loco/wagons/carriges are both coupled up throughout the train on a single pipe only the bags with the red handle are coupled.
We now come onto brake timings, on a loco and some types(not all) of freight wagon there is a pass/goods change over lever this changes the timing of the brake. All passanger trains,and freight trains timed to run at 65mph run in the pass timing, freight trains timed to run at 60mph or less run in the goods timing.The diff being that pass timing applies and releases the brake much quicker that in goods (dont ask me the timings as I don't know).
With a freight train in goods and the brake applying slower I assume it cause less wear and tear on the vehs and the track.
There are exceptions to the above as there is throughout the whole NR rulebook but these are far to many to go into on a forum like this but I hope this helps a little.

Les

Oops ! :o

but thanks for the explanation, Les.

I'll second Shed Cat's comments. Thanks Les, your explanations go a long way towards explaining matters.
To go back to my original TSR query, I am now starting to think that the two light engines that I saw going "noticeably slower" than the passenger trains were doing so for completely different reasons. Today I saw a light engine pass through the TSR much faster than the other two and certainly way above the speed that freights do.
Your mention of light engine speed limits does, however, bring one question to mind....... Would a consist of say 5 locos coupled together still be subject to the same conditions as a single light engine?

Would a consist of say 5 locos coupled together still be subject to the same conditions as a single light engine?[/QUOTE]

Depends as to why 5 loco are coupled are they,

1. in multy
2. in tandem

To explain if loco's are in multy that means the loco are all coupled up electrically and can be controlled by 1 driver getting power from all locos.

Or in tandem is the locos are not coupled electrically, can be worked by 1 driver but power from the lead loco only.

To try and answer the querie, I think providing all the locos are in good working order with no brake problems etc then yes I believe that 5 light locos are classed the same as 1 but I will find out and get back soon.

Les

Les,
I assume that the consists I am thinking of are not running in multiple because they are often mixtures of 66's and 60's. I don't think 60's and 66's can multiple together, can they?
It is nearly always on a Saturday afternoon when I see them so I assume that they are travelling from the EWS depot at Warrington to Crewe ready for PW duties on the Sunday.

Your spot on a 66 can only multi up with another 66/67 or a 59.

Les

kinda confusing....just as you think theres a simple explination theres another explination to go with it that raises more questions! Certainly a complicated subject!

locomotives working in multiple are down to the connectors linking each locomotive not the coupling of the trains.

so if a class 60 was attached to a class 66 they wouldn't be able to work in multiple, one of the locomotives would be "dead" or running idle if the engine was running.

Class 59's Class 66's and class 67's can work together in powering trains as they use a system called AAR or something like that its called.

But going back to speed restrictions. The class 66 differs from the class 59 in the sense that the wheels follow the curvature of the track as the end wheels of each boogie are self steering thus preventing rail wear so would be interesting to know if there is a difference for class 66 on speed restictions if it goes on wear and tear on some things.

Plus class 59's (not sure about the 59'2's tho) have some sort of computer control thing that controls the amount of wheel slip on the rail...allowing the wheels to slip by a certain amount on pulling away from a heavy start but the amount they are allowed to slip by is small.

but would be interesting to know if things like that affect speed restrictions on loco's.

The simple answer is NO to the different class of loco on speed restrictions, a differential speed restriction applies to the class of train not the loco.

As for the 59/2, Yes they have a system on them called creep control this basically works similar to the 66/67 in that when the computer detects the wheel starting to slip (not slide) then the system will automatically start to apply sand to the rails, this is what you see when a 59/66 or a 67 is pulling away and you see a dust trail from the leading bogie. The system will cut out in normal conditions at about 10mph unless the computer detects poor rail conditions by continuos wheel slip.
In the case of a train sliding then the sand has to be applied manually by the conrol lever in the cab by the driver.

To explain slid/slip, Wheel slip occurs under power when pulling away etc and wheel slide occurs usually under braking conditions.

Hope this clears a few thing up.

Les

Ok Les, here's some questions for you. (I don't know the first thing about locos, as I only ever drive EMUs).

1) If a loco like a 66 is dead and all the air has leaked out of the main res and brake cylinders, does it have a spring operated safety brake, or will it run away if you haven't applied a handbrake ?

2) If you are in tandem with another 66 (so that presumably you're effectively hauling it dead), do you have to isolate the brakes on the other unit, or what do you do ?

TIA

Foggy

Simple answer to point one is yes it will run away if the parking brake is not applied and/or scotched.

Point two is yes we isolate the brake unit, also known as the E70, from inside the clean air air compartment, What this does, in laymans terms is it stops the brake pipe control on the DIT loco but allows the brakes to apply when operated from the lead loco.

It gets a bit more complicated if the loco is a failure and gets assistance from the rear, We have to isolate the E70 and the AFT cock (assistance to failed trains) which allows us to move the train with the failed loco dead therefore unable to maintain 72.5psi in the brake pipe, used only to clear the line so that a working loco can be put on the front of the train.

Not forgetting that a brake test MUST be carried out after attaching a loco to the failed train.

Hope you can understand that basic explanation, its harder to explain than do.

Les

Like most things on the railway. :D

And thanks for the clear and concise explanation Les

Speed signs
 

The lower speed always applies to Goods Trains which unless composed of empty wagons, are likely to be significantly heavier than passenger rolling stock and thus present a higher risk of derailment through PW works unless so restricted.
Roger (BR Retd)

Thanks for that Roger.
It's good to see that these old threads are still being looked at.

Good to see you posting John.

Happy New Year.

John H-T.

That said I only just got the thread posted up and the images originally there are not the website has been removed and the domain is for sale

Glad to see someone from Blandford Forum! Started my railway career at the end of 1963 at Wimborne and later had a spell in the Booking Office at Blandford. Ended up in an office on the 3rd floor at Waterloo!
Roger

anyone got a cut out 20 0r 25 MPH speed sign for sale or in exchange for a 30 or 40?
[email protected]
01507 463630

G'day,
Just found this thread and will toss in my two bob's worth.
Here in NSW we have three specific train speed boards in use as distinct from temporary speed restrictions.
Where the high speed XPT wanders, there will be a silver board denoting the sectional speed for it.
Where medium high speed DMU trains operate, there will be a blue board denoting the sectional speed for such.
And, all track sections have the yellow board which denotes the sectional speed for locomotive hauled trains.
The yellow boards may indicate a relatively high sectional speed, up to a maximum of 115 kph.
But, that does not indicate that freight trains can percolate at such speed.
Only high wheeler freight with high speed bogies through-out the train can operate at top locomotive hauled speeds.
Most freight is limited to a maximum of 80 kph.
And certain slow speed bogies restrict the speed further.
The train crew must know the specific speed permitted for their freight consist.
Light Engine movements are also limited to a maximum sectional speed.
Locomotives are heavy and will take longer to stop if travelling at high speed.
This is determined by the locomotive brake type.
Some locomotives only possess one brake block per wheel, while others possess two brake blocks per wheel.
The single brake block per wheel design is to prevent the wheels from locking up and skidding.
When descending steep grades Light Engine, it is a general requirement that the locomotive have a working dynamic or regenerative brake.
Where trackwork has occurred, or due to a track defect, a temporary speed restriction is applied.
Again, two small speed signs may be attached to advise of the speed for loco hauled trains or the XPT.
The XPT sign will indicate a slightly higher speed limit to that for the loco hauled.
Where no DMU sign is utilized, any DMU train must travel at the loco hauled speed indicated.
Our temporary speed restrictions may also possess a time sign.
The time sign indicates the period during the day when the speed restriction applies.
This generally being the case during summer and hot temperatures.
Steve.

Thanks for that Steve.
It's always good to have an input to a subject from another part of the World.

G'day John,
I am always intrigued by the various lineside signage that is utilized around the globe.
Steve.

Coming to this a bit late, but here's a bit of meat.

Differential boards can also apply to Permissible Speeds (what most of know as linespeed - before NR muddied the water) as well as Temporary (TSR) & Emergency (ESR) speed restrictions.

The signs section of the rulebook (linky here...UK Rulebook) deals with it if you want some late night reading. What we want currently hides on page 802

"Differential temporary speed restrictions

A temporary speed restriction can show different speeds which apply to different types of trains. The bottom figure always indicates the higher speed. It applies to:
•
passenger trains (loaded or empty)
•
parcels or postal trains (loaded or empty)
•
light locomotives.

The top figure applies to all other trains"

Most ESRs, and many TSRs are imposed because of track condition, so the speed is set to allow trains to keep running until the P-Way women & men (god bless 'em) can get out and fix it.

We get some quite hefty differential ESRs on the ECML, such as 30/100 on a Permissible Speed of 125mph. This is usually for the condition of the track or crossings. Passenger trains usually weigh between 20-40 tons per coach (though I stand to be corrected), whereas some of the sand/aggregate trains can weigh up to 100 tons per hopper. You wouldn't want that monster hammering over a weak rail at 60MPH.

BW

Thanks for that BW.

G'day BW,
I have snagged your GERM 8000 pdf.
Sounds like something that you require detergent and gloves to handle.
I will gradually peruse the instructions to glean just how you lot do it differently from us lot.
Here, we now have the TOC (Train Operating Conditions) manual.
This details all operational facets and safeworking systems within the NSW rail network.
I am familiar with the NSW TOC manual.
However, other state systems have slightly different operating conditions and safeworking.
I remember the panic approach to the smog hollow 2000 Olympics.
Three drivers were seconded to Transport House for a week to review the proposed safeworking alterations.
I represented the Freight section.
All three of us were gobsmacked at a couple of the management machinations.
Fearing a shortage of drivers, management proposed hiring some MET drivers from Melbourne Victoria.
HMMM!
I could imagine the chaos had this ploy gone ahead.
Them Mexicans possessing an adapted USRR Speed Signalling system.
Whereas, here in NSW we have Route Controlled signalling system.
Green over Red in Melbourne means Clear Normal Speed.
Green over Red in smog hollow means SLAM the brakes on as the next one will be All On.
Not only signalling can be different between various state systems, but also lineside signs etc.
We also shook our heads at some other whims.
It was also feared that an emu might stall on the 1 in 30 grade around the Olympic balloon loop.
So, management planned to hire a 48 class DL531 950 hp diesel from Freightcorp.
I asked two simple questions; what is the load for a 48'er on a 1 in 30, and what does an 8 car emu weigh ?
Knowing that the average 8 car emu weighs 380 tare tonnes, some weighing much more.
Plus, that a 48'er is only capable of lifting 253 tonnes on a 1 in 30, I suggested that they had better hire an 81 class.
An 81 class JT26C-2ss 3000 hp capable of lifting 745 tonne on a 1 in 30.
Naturally Freightcorp would charge Cityrail much more to hire an 81 class.
Steve.

The people from Victoria are Mexicans/ Those from New South Wales are Cockroaches/
Those from Queensland are Bananabenders; if anyone wants to know.