How to read gradients?

I've been wondering, how do you read gradients when they are written down like this?

1 in 1642 on the left hand side of the sign, 1 in 191 on the right.

Chris

with it being a summit rather than a change in steepness on the same slope?

Oh yeah, that as well...

Or Downhill both ways

Aye, if it was a change of steepness on the same slope they would both 'point' the same way wouldn't they?

The centre-point of the gradient marker represents the change point, so to the left will be one gradient and to the right will be the other gradient. These can be any combination of rising, falling, or level.

However how many are actually accurate?
To me they are just an indication of a steep bit or not so steep bit.
They really only refer to the average grade on that section of line not the real gradient to be found when surveying. (I have found a short section of 1 - 20 within a 1 - 49 marked grade)
Not just me either as can be seen if you read the foreword to the NERAs publication on North Eastern Railway gradient sections.

Ploughman said:

However how many are actually accurate?
To me they are just an indication of a steep bit or not so steep bit.
They really only refer to the average grade on that section of line not the real gradient to be found when surveying. (I have found a short section of 1 - 20 within a 1 - 49 marked grade)
Not just me either as can be seen if you read the foreword to the NERAs publication on North Eastern Railway gradient sections.

Click to expand...

I have never taken any notice of what a gradient is in number I judge a gradient on how much power you need to climb and how much brake you need to stop

Gradients are required to design a Temporary Speed Restriction.

Ploughman said:

However how many are actually accurate?
To me they are just an indication of a steep bit or not so steep bit.
They really only refer to the average grade on that section of line not the real gradient to be found when surveying. (I have found a short section of 1 - 20 within a 1 - 49 marked grade)
Not just me either as can be seen if you read the foreword to the NERAs publication on North Eastern Railway gradient sections.

Click to expand...

They are only as accurate as when they were applied, which is normally during construction of the original line.

As you say the gradient is averaged out between the two points, and of course subsequent track work may well have altered this, but not significantly.

On the new buidl lines I have worked on, the gradients are derived from the formation design, and the change point is where there is a significant chnage in the gradient of the terrain. Different Railway systems will have their own policy on what represents a significant change sufficent to trigger the installation of a gradient post, but you can consider it to be a change where there is likely to be an impact on the handling of the train, such as compression or expansion.

Many heavy haul railways prohibit more than two changes of gradient underneath the train at any point which means that the gradients tend to change not more frequently than around 1 to 2 miles separation at the most, and then only by small amounts.

We generally try to install passing loops on level ground, or at least level out the length where that is possible.

Poss Planner said:

Gradients are required to design a Temporary Speed Restriction.

Click to expand...

Gradients are also required for signal section lengths