Why the unusual exit signal at Bedzin?

[NeatKefe]

To set exit signal, e.g. E2, I must first set D when exiting towards Dąbrowa Górnicza. In the notes for the station it says this is “a safety aspect”. What safety aspect would that be? I’m struggling to understand the purpose of signal D, and I haven’t seen this setup anywhere else. Are there more examples out there..?

[Shiralyn]

Łódź Chojny has a similar exit but this is due to a crossing, I'm also interested in the answer.

[pan kura]

I wouldn't say it's a safety aspect nor is it directly connected with a crossing. The real answer is hidden in the rule books. According to Ie-4 §51 ust.6

and §8 ust. 1, 2

If the breaking distance from signal A to signal B is greater than twice the length of braking distance for a given railway line, a distant signal paired with home signal B must be installed...

..another signal can be placed in between. For explanation purpose let's name it signal C

This is also the case in Będzin. Due to the fact the braking distance for this section of lk1 was 700m a few years back and the distance from signal E2 is to ABS signal 3036 is ~1.7km (L>1400m), an additional signal (E2->D->3036) had to be placed.

 

[jeroezie]

Is that not a very expensive and inflexible solutuin? An simple ABS sigbal would do just fine in the Bedzin case. And it does not anwser the hard interlocking requirment enforing the extra signal to be clear for the sigal inside the station to be clear (usually it would be silly to hace a train depart in yellow but now it has been made 100% impossible in a weird siruation it would have been needed).

[pan kura]

Cytat

Is that not a very expensive and inflexible solutuin? An simple ABS sigbal would do just fine in the Bedzin case.

Not really that expensive, a couple more relays and an additional signal. Far less expensive solution than adding extra ABS block or moving closer 3036 signal. Furthermore it was quite a popular method to interlock mechanical systems with ABS on the line.

Cytat

And it does not anwser the hard interlocking requirment enforing the extra signal to be clear for the sigal inside the station to be clear (usually it would be silly to hace a train depart in yellow but now it has been made 100% impossible in a weird siruation it would have been needed).

Again. The real answer is hidden in the rule books - Ie-4 §13. ust.6

TLDR; because there isn't 700m (minimum breaking distance) between signal E2 and D in Będzin and ABS status isn't directly interlocked with those two signals (cost reduction), signal D has to be cleared first

Edited 18 hours ago by pan kura

[longmun_]

Very interesting, thank you! Is it vaguely the same thing happening at Sk M PZS, Gr P1-4 and who knows where else? Also, LK1 at Zw towards Myszków has those starting block signals. I guess they are there for the same reason, but perhaps the braking distance isn't reduced between E4-7 and these signals, thus they were fine as ABS?

[pan kura]

28 minut temu, longmun_ napisał(a):

Is it vaguely the same thing happening at Sk M PZS, Gr P1-4 and who knows where else?

Yeah. Iirc such solution can be found in Skierniewice, Bedzin, Grodzisk Maz., Łódź Chojny, Katowice Zawodzie, Kutno

56 minut temu, longmun_ napisał(a):

I guess they are there for the same reason, but perhaps the braking distance isn't reduced between E4-7 and these signals, thus they were fine as ABS?

it actually is reduced to 400m as the max. speed on route E4 -> 2728 is only 40km/h so all standards are met