Differential Speed Restrictions

[rogerbun]

Originally Posted by swisstrains

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?

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)

[swisstrains]

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

[John H-T]

Originally Posted by swisstrains

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.

[Madcaravanner]

Originally Posted by swisstrains

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

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

[rogerbun]

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

[rogerbun]

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

[aussiesteve]

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.

[swisstrains]

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

[aussiesteve]

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

[Beeyar Wunby]

Originally Posted by swisstrains

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

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