explain gradients

[furnessvale]

We don't, routinely. The NMT can measure altitude and location, but does hiccup at times. The trouble is that the measured track profile is smoothed out by tampers over the years and has no dclearly efined "changes"; it's OK to measure level changes between any two points though.

So combining your thoughts and The Planner's, there is definitely a need for updated gradient information.

Surely a case for a modification on the measurement train.

 

[3141]

Yes, it is called spurious accuracy.

That said, tan16.09 (~40%/1 in ~2.5) is very steep. If I recall correctly, hardknot pass is 1 in 3 at its steepest.

1 in 3 is what I've always understood to be the gradient of Hardnott Pass, and it certainly seemed like that when I drove up it 35 years ago. I remember an article in the Guardian in the 1960s where the writer had enjoyed watching cars going up and the drivers thinking it was quite easy till they got to a bend followed immediately by a much steeper section, where they stalled because they hadn't yet engaged first gear.

When I was in primary school I remember being told about gradients, expressed in those days as ratios, and my recollection is that most people understood that 1 in 4 is very steep, whereas if a road is 1 in 20 you'd hardly feel it mattered, but would be highly unusual for a railway.

When road gradients began to be expressed as percentages, my way of converting them was to divide the percentage into 100. E.g. if it's 25%, 100/25 = 4 so the gradient is 1 in 4. 12% is 100/16 = 8 and a bit, so it's moderately steep at 1 in 8.3. 10% or less and you wonder why they bothered to tell you.

 

[Railsigns]

I agree with Mr Locke the gradient information has probably not been updated for years, perhaps not even since the lines were originally built.

Just to demonstrate that gradient information was sometimes updated (I have several more of these):

 

[jopsuk]

10% or less and you wonder why they bothered to tell you.

I think there's only a requirement on the roads to sign gradients of 10% or more?

Relevant to railways: guidance for wheelchair accessible pedestrian ramps is that they should be no more than 5% and should have flat sections (if I recall correctly) every 10m of horizontal distance. This is why new ramped footbridges are so massive- that and the need to build any new structure so that it clears any OHL or future OHL without modification to the structure or lines.

 

[D1009]

If we do then Ive never seen it, we have always gone off signalling diagrams and 5 mile diagrams, even an old Ian Allen gradient map book!

I've still got my Ian Allan gradient book, and the page covering the Settle and Carlisle still shows evidence of the soot from the Jubilees which I travelled behind in 1967!