ScotTrainLad
Member
Just interested in how speed limits were set.
Primarily safety. For example.Just interested in how speed limits were set.
Considering this is in the Railway Discussion section, I doubt we are...If we’re talking speed limits on roads, parish councils have an input so they can be quite subjective and based on local politics.
One of the familiar experts on this board has mentioned the number of factors that need to be taken into consideration before increasing a speed limit. If I remember correctly he said it was more than 80.
Tail wagging the dog. Permissible speed usually determines braking distances, not the other way around.Braking distances. The right to speed is dictated by the ability to stop!
That's not how signalling works...Tail wagging the dog. Permissible speed usually determines braking distances, not the other way around.
Yes, it is.That's not how signalling works...
OK, let's be pedantic. To run a single captive train at any speed does not require a signalling system but that wasn't my point. I'm a signalling engineer by the way...Yes, it is.
I'm a signalling schemes designer, by the way.
Which was exactly the mistake that the German Maglev trial system with just one train made, culminating in their disastrous accident.OK, let's be pedantic. To run a single captive train at any speed does not require a signalling system but that wasn't my point. I'm a signalling engineer by the way...
Yes, based on driveability and also consideration for standardising line speeds in both directions to reduce driver workload.Some limits between Chinley and Hazel Grove have just been reduced based on what is actually achievable versus what you *could* do.
Yes, it is.
I'm a signalling schemes designer, by the way.
What comes first? Do we say "we want a 100mph railway, design the signals to cope with it" Or do we say "This is where the signals are, how fast can we go?"OK, let's be pedantic. To run a single captive train at any speed does not require a signalling system but that wasn't my point. I'm a signalling engineer by the way...
We say the former (and we want this timetable with these trains so make sure it can accommodate that too please).What comes first? Do we say "we want a 100mph railway, design the signals to cope with it" Or do we say "This is where the signals are, how fast can we go?"
How long the blocks are , are based on the speed/stopping distance are they not?OK, let's be pedantic. To run a single captive train at any speed does not require a signalling system but that wasn't my point. I'm a signalling engineer by the way...
They also increased speed limits for regular trains at a point in the 1980s I recall, so the Colwich-Cheadle Hulme line speeds increased from 85mph to greater numbers such as 95mph.Speed limits around bends are set for passenger comfort. Hence when BR resarch showed that it was possible for trains to go 40% faster round the bends without risk of derailment, they proposed the Advanced Passenger Train with tilt so that it could go 40% faster round the bends.
Almost certainly not. If such a thing did exist, how would it account for cant?Is there a clear plastic graduated gauge available that can be laid over an ordnance survey map to give you an indication of speed of a rail curve?
another problem is if there room for a well laid out transition curve (where the radius get gradually smaller or greater each side of a curve. Too short a transition curve would cause the train to lurch so a slower speed would be better. Stations, junctions and structures could affect transition curves.Almost certainly not. If such a thing did exist, how would it account for cant?
You could have a tool which helped you to measure the horizontal radius of a curve. Many years ago I made a crude tool with greaseproof paper (semi-transparent), a pencil and a pair of compasses, when I was interested in road design. You could then see what was the cant required for any specified speed or vice versa, and the maximum speed assuming maximum cant.Almost certainly not. If such a thing did exist, how would it account for cant?
I think that was the case on some lines from the 1960s. First generation units were restricted to 70 mph, so some line limits were reduced tp 70 mph (e.g. Wigan / Southport.)if a line isnt scheduled to see stock faster than, say, 75mph max speed (and so all services are timetabled accordingly), is it considered that there is "no point" maintaining it to a standard for higher speeds and the limit set accordingly?
Avanti 221s still tilt.Tilting Voyagers (I appreciate they no longer tilt),
Good to know - still a pain in the sectional appendix and when you do the speed calcs!Avanti 221s still tilt