Tripping past signals

[Chris M]

At least two trains today (the one I was on and the one ahead of it) had to be tripped past the station starter on the northbound Bakerloo Line at Oxford Circus today. At least that's what I assume was happening as we progressed about half a carriage length into the tunnel before coming to a stop with a clunk and hiss of air, followed by proceeding at not much more than walking pace most of the way to Regents Park. However, the train operator did not make any announcements at all and there were some worried looks in the car I was in, some of which turned to rather perplexed looks when we resumed normal line speed.
I thought that when it was known in advance that, for whatever reason, the train would have to be tripped past a signal that the driver was supposed to make an announcement to the train explaining what was going to happen ("applying a routine safety procedure" or something like that?) so as not to worry passengers (there was a person at the headwall talking to the driver, presumably advising them about the failed signal)?
This is the first time I've been on a train that's been tripped in this manner, and the stop was quite a jolt even at the low speed. It was a quiet time (about 11:15) so there weren't any standees, but had I been standing and just leaning (just as I was doing on the Central Line last night) I could quite easily have fallen over. I imagine that there must be even more of a risk of this if a stick is hit at full speed.

(ps I couldn't decide whether this thread belongs here, trains technical, the Bakerloo board or general LU/TfL, so feel free to move if if you think I plumped for the wrong one)

[North End]

Jan 23, 2010 22:19:08 GMT Chris M said:

At least two trains today (the one I was on and the one ahead of it) had to be tripped past the station starter on the northbound Bakerloo Line at Oxford Circus today. At least that's what I assume was happening as we progressed about half a carriage length into the tunnel before coming to a stop with a clunk and hiss of air, followed by proceeding at not much more than walking pace most of the way to Regents Park. However, the train operator did not make any announcements at all and there were some worried looks in the car I was in, some of which turned to rather perplexed looks when we resumed normal line speed.
I thought that when it was known in advance that, for whatever reason, the train would have to be tripped past a signal that the driver was supposed to make an announcement to the train explaining what was going to happen ("applying a routine safety procedure" or something like that?) so as not to worry passengers (there was a person at the headwall talking to the driver, presumably advising them about the failed signal)?
This is the first time I've been on a train that's been tripped in this manner, and the stop was quite a jolt even at the low speed. It was a quiet time (about 11:15) so there weren't any standees, but had I been standing and just leaning (just as I was doing on the Central Line last night) I could quite easily have fallen over. I imagine that there must be even more of a risk of this if a stick is hit at full speed.

(ps I couldn't decide whether this thread belongs here, trains technical, the Bakerloo board or general LU/TfL, so feel free to move if if you think I plumped for the wrong one)

Yes, Train Operators are required to make a PA to passengers, advising that there will be a slight jolt and to sit down or hold on. The jolt is actually less of an issue if the train does get tripped from full speed, because everyone knows the brakes are on and subconsciously prepare themselves for it, when done from low speed it comes as a surprise.

It is possible that the trains weren't expecting to be tripped though. We had an incident on the Northern Line a little while ago where one particular train was repeatedly being tripped on one particular station starting signal, even though the signal was green. It transpired that the can guard on the trainstop housing was fractionally high, and the tripcock on that individual car was at the low end of the tolerance range.

[railtechnician]

Jan 23, 2010 22:47:37 GMT North End said:

Jan 23, 2010 22:19:08 GMT Chris M said:

At least two trains today (the one I was on and the one ahead of it) had to be tripped past the station starter on the northbound Bakerloo Line at Oxford Circus today. At least that's what I assume was happening as we progressed about half a carriage length into the tunnel before coming to a stop with a clunk and hiss of air, followed by proceeding at not much more than walking pace most of the way to Regents Park. However, the train operator did not make any announcements at all and there were some worried looks in the car I was in, some of which turned to rather perplexed looks when we resumed normal line speed.
I thought that when it was known in advance that, for whatever reason, the train would have to be tripped past a signal that the driver was supposed to make an announcement to the train explaining what was going to happen ("applying a routine safety procedure" or something like that?) so as not to worry passengers (there was a person at the headwall talking to the driver, presumably advising them about the failed signal)?
This is the first time I've been on a train that's been tripped in this manner, and the stop was quite a jolt even at the low speed. It was a quiet time (about 11:15) so there weren't any standees, but had I been standing and just leaning (just as I was doing on the Central Line last night) I could quite easily have fallen over. I imagine that there must be even more of a risk of this if a stick is hit at full speed.

(ps I couldn't decide whether this thread belongs here, trains technical, the Bakerloo board or general LU/TfL, so feel free to move if if you think I plumped for the wrong one)

Yes, Train Operators are required to make a PA to passengers, advising that there will be a slight jolt and to sit down or hold on. The jolt is actually less of an issue if the train does get tripped from full speed, because everyone knows the brakes are on and subconsciously prepare themselves for it, when done from low speed it comes as a surprise.

It is possible that the trains weren't expecting to be tripped though. We had an incident on the Northern Line a little while ago where one particular train was repeatedly being tripped on one particular station starting signal, even though the signal was green. It transpired that the can guard on the trainstop housing was fractionally high, and the tripcock on that individual car was at the low end of the tolerance range.

Mmm! The can guard is not the brightest of ideas and I often wondered whether on balance they contributed to more trainstop failures than they prevented. The turbulence of passing trains as they accelerated out of stations had a habit of sucking up tin cans and dropping them into the 'Roman helmet' fouling the arm even as they were squashed. Of course having such a guard surrounding the arm made extracting trapped cans a little more difficult !