non-reciprocal locking

[onestrangeday]

Hi PJW:

thanks for your clear explanation, I have better understanding on the term of clearance point, fouling point and flank protection. I think I have mixed up with the fouling point and flank protection, there are difference between them.



thanks




william

thanks for your clear explanation. Yes, I have understood what it means. I think it is due to my lack of signalling knowledge, I found some of the explanation in the book (railway signalling) is hard to understand. So I might asking more questions in the future.

Indeed, happy that you ask such questions in future. Rather surprised that more people don't!

One more thing I would like to ask, how do a fouling point is marked on the layout (British Practice) ? because in the book, i cannot see any marking on the diagram that point out the fouling point. (or is there always flank protection for the crossing ?)

As the railway line i have exposed to in the past, there is always letter "F" marked on the layout to show the reader that the section is protected by the flank protection (due to the track next to each other is close enough that a train side collision might happen, as this often the case in depot.). Whereas, if it not marked by the letter ''F'', there is no flank protection.
william

Nowadays we always mark the Clearing Point as "CP" with a double headed arrow, but traditionally (as in the era of this book) it was generally only indicated for those sites which are tight and in particular where there is an IRJ which is foul. Note that the Clearing Point is further from the place of covergence than the Fouling Point which isn't marked (the FP is the place where the vehicles would actually just hit, whereas the CP is the place where the train detection limit needs to be i order to ensure a decent "passing clearance" as well as taking into account the fact that it is the corner(s) of the vehicles hich would hit whereas the train detection only knows where the wheels of the vehicle are located and there is always a degree of "overhang"- the vehicle is longer than its wheelbase.

Also be careful that "foul" isn't precisely the same as "flank"; do you understand the distinction?

We would (almost always) call and lock points as flank where they have the opportunity to deflect a train that has SPADed a protecting sgnal from collision path with the set route, irrespective of how "close" it is to the route in question.

What we mean by Foul is where the adjacent train detection section commences too close to the convergence for us to be sure that there is adequate clearance between a vehicle standing on it and one on the other route. For simplicity a train detection section would always extend sufficiently sideways from the line of the set route to prove that it would be safe to allow the passage of a train on that route, this is not always practicable and the joint between sections has to be placed within this distance. This seems to be what you are calling "Flank".