"TPWS Activation: A Driver's Reflection"

[Railsigns]

I wasn’t aware of that. But the idea of ‘most’ of them being 12.5 doesn’t make me want to test any of them just in case.

No, I wouldn't want you to test them either . If you were really curious, you could roughly measure the distance between the two loops from the platform edge. 4.5 metres gives a set speed of 10 mph, and 5.5 metres gives a set speed of 12.5 mph.

 

[43066]

Most buffer stop loops are set at 12.5 mph. 10 mph was originally the standard set speed for buffer stop loops, but this was increased to 12.5 mph after a few years.

Is there anything official on that, out of interest?

 

[Railsigns]

Is there anything official on that, out of interest?

Yes; Network Rail Technical Instruction TI 025 "TPWS Loop Positioning - Buffer Stops", dated February 2006.

 

[43066]

Yes; Network Rail Technical Instruction TI 025 "TPWS Loop Positioning - Buffer Stops", dated February 2006.

Thanks very much.

It doesn’t seem to be online, sadly. I don’t suppose you have a link you’d be able to share?

 

[Railsigns]

It doesn’t seem to be online, sadly. I don’t suppose you have a link you’d be able to share?

I don't have a public link for that, sorry.

 

[Stossgebet]

It's another reason trains are slower in the snow. "There's grids here somewhere, can't see them, better brake earlier or harder just to be sure"

 

[LoogaBarooga]

There are requirements for additional running brake tests when it's snowing so I'm no sure that's necessarily true.

 

[AverageJoe]

There are requirements for additional running brake tests when it's snowing so I'm no sure that's necessarily true.

Not sure that helps you see the grids
Which I presume is what he meant.

 

[Stossgebet]

There are requirements for additional running brake tests when it's snowing so I'm no sure that's necessarily true.

Yeah, I did say "another reason". But my comment was a bit tongue in cheek.

 

[LoogaBarooga]

Ah apologies in that case, I completely misinterpreted your post!

 

[SiTheTrainGuy]

No, I wouldn't want you to test them either . If you were really curious, you could roughly measure the distance between the two loops from the platform edge. 4.5 metres gives a set speed of 10 mph, and 5.5 metres gives a set speed of 12.5 mph.

Is that legit? Surely they could space them the same width apart but just change the activation time between arming and trigger loop to change the speed it is set for?

 

[Railsigns]

Is that legit? Surely they could space them the same width apart but just change the activation time between arming and trigger loop to change the speed it is set for?

The distance between the two OSS loops is what determines the set speed. Since the TPWS timer on board trains runs for a fixed duration (0.974 seconds for passenger trains and 1.218 seconds for freight trains), you can calculate the set speed (for both passenger and freight) of any OSS if you know the distance between the loops. Altering the duration of the train's timer would change the set speed of every OSS on the whole network.

 

[SiTheTrainGuy]

The distance between the two OSS loops is what determines the set speed. Since the TPWS timer on board trains runs for a fixed duration (0.974 seconds for passenger trains and 1.218 seconds for freight trains), you can calculate the set speed (for both passenger and freight) of any OSS if you know the distance between the loops. Altering the duration of the train's timer would change the set speed of every OSS on the whole network.

Never knew that! Good knowledge. I’ll still drive over them at 8mph (approaching buffers) just to make sure though

 

[NSEWonderer]

Classic Distance / Time = Speed

 

[choochoochoo]

There isn’t enough openness when incidents occur for drivers to learn from others mistakes. I understand the offending driver is entitled to some privacy, but drivers are pretty good at detective work and figuring out who had the incident.

Whilst most depots have a spad notice case, other incidents aren’t as well publicised and details are only gained from mess room discussion.

I talk to pilots and they tell me that are all made aware of any incidents that happen pretty soon after they happen and the findings of the investigation are made available via a briefing document. Why can’t we have this on the railway ?