Birmingham New Street tunnel - acceleration

[brick60000]

Hi all,

A question that has been on my mind the last few times I've departed from Birmingham New Steeet towards Wolverhampton on a LNR 350.

There is a period of fast acceleration, followed by relatively heavy allbeit brief deceleration towards the end of the tunnel, before the unit then accelerates out of the tunnel mouth. Does anybody know why this deceleration happens, and why a more gradual acceleration throughout isn't applied?

I've no doubt there's a logical reason!

 

[hexagon789]

Hi all,

A question that has been on my mind the last few times I've departed from Birmingham New Steeet towards Wolverhampton on a LNR 350.

There is a period of fast acceleration, followed by relatively heavy allbeit brief deceleration towards the end of the tunnel, before the unit then accelerates out of the tunnel mouth. Does anybody know why this deceleration happens, and why a more gradual acceleration throughout isn't applied?

I've no doubt there's a logical reason!

Running brake test?

If the train originates at Birmingham New Street or a fresh driver takes over there, then the rulebook requires a running brake test to be carried out before I believe either a station stop or permanent speed restriction to test the brake is performing in line with the drivers expectations after a train has either started a journey or a new driver takes over.

Generally when I get a train out of Glasgow Central, for instance, the driver will make a hard but short brake application, then power up again long before reaching the next station out.

 

[rdeez]

I've noticed something similar in the Gloucester-bound tunnels leaving New Street, which would fit in with the answer given above. There's a period of acceleration (I think the line speed is 20mph as you enter the tunnel), often (but not always) followed by a brief but fairly sharp brake prior to hitting the 30mph line speed part way through, when speed then picks up again.

Doesn't always happen, which would make sense if it was sometimes a 'fresh' driver doing a brake test.

 

[whhistle]

While unlikely, might it be a very short period of a temporary speed limit?

 

[Bald Rick]

Definitely a running brake test.

 

[route101]

Running brake test?

If the train originates at Birmingham New Street or a fresh driver takes over there, then the rulebook requires a running brake test to be carried out before I believe either a station stop or permanent speed restriction to test the brake is performing in line with the drivers expectations after a train has either started a journey or a new driver takes over.

Generally when I get a train out of Glasgow Central, for instance, the driver will make a hard but short brake application, then power up again long before reaching the next station out.

Ah i was thinking it was to do with signals at Glasgow , i see now

 

[brick60000]

Thanks all for the reply! I hadn't thought of that - but makes perfect sense as the Liverpool's originate from New Street .

 

[hexagon789]

Ah i was thinking it was to do with signals at Glasgow , i see now

Sometimes you do get restrictive aspects going out of Glasgow Central, Barrhead trains in particular seem to conflict with an incoming train off the Cathcart lines but on 156s going out towards East Kilbride/Barrhead I generally find most drivers make a brake application just before Muirhouse North Junction, usually fairly light (presumably Step 1) killing off many be 5mph in speed, then back into Notch 7 to accelerate back to 30mph.