Differential Speed Restrictions

[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?

[GWR9600]

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.

[tonyharker]

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

[swisstrains]

Originally Posted by tonyharker

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?

[LesG]

Originally Posted by swisstrains

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

[swisstrains]

Originally Posted by LesG

...............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.

[Shed Cat]

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?

[LesG]

Originally Posted by swisstrains

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.

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

[LesG]

Originally Posted by Shed Cat

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?

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

[Shed Cat]

Originally Posted by LesG

Shed Cat you are actually straying off on a whole different ball game

Oops !

but thanks for the explanation, Les.