Differential Speed Limits

[Ardvarna]

Can anyone direct me towards technical information/ official guidelines on the use of differential speed limits for DMU v Loco hauled trains in the UK. I understand that certain lines allow DMUs and Sprinters to travel at higher speeds than loco hauled trains due presumably to they being lighter with greater breaking capacity.

 

[Craig]

http://www.railsigns.co.uk/sect13page3/sect13page3.html

This page would probably be a good starting point.

 

[Ardvarna]

Thanks Craig. Thats very helpful.

Anyone aware of published guidelines or engineering papers justifying the case for higher speeds being permitted for DMUs/Sprinters.

 

[Dennis]

Group standards have probbly got the information hidden away somewhere;

try these for starters (although they don't contain an explicit description of enhanced braking);

http://www.rgsonline.co.uk/docushare/dsweb/Get/Rail-41397/Rt0034a.pdf

http://www.rgsonline.co.uk/docushare/dsweb/Get/Rail-43675/SP_3.PDF

Also, differential speed limits may be applied as a consequence of track condition - the higher track forces associated with heavy vehicles may require lower speeds to limit the potential for track damage.

 

[Ardvarna]

Thanks Dennis.

 

[Ardvarna]

Still on the subject of speed restrictions - is there a published standard governing permanent speed restrictions or route upper speed limits. Or is it down to the mood of the civil engineer or safety officer?

 

[TheSlash]

Alot of it is down to the track maintenance. The Chandlers Ford line has split speed limits for Freight and Passenger trains.
It allows a reasonable speed of Passenger train without much maintenance as the wear and tear done to the track by a freight train is reduced by running freight at lower speeds

 

[The Planner]

Still on the subject of speed restrictions - is there a published standard governing permanent speed restrictions or route upper speed limits. Or is it down to the mood of the civil engineer or safety officer?

It's all down to a number of factors. Signal sighting, traction braking capability (appendix a, b and c braking curves), infrastructure capability (track cant, embankments, structures etc...), whether the train can actually reach the line speed. Then you have the 3973s which apply to freights with out of gauge wagons, dangerous cargo etc...theres several more than I cant think of at the mo.