Speed check Shrewsbury to Wellington

[Bertiethebobby]

I have a question that has been bugging me for ages and am hoping that someone here will be able to answer it.

When trains are on route to Wellington from Shrewsbury, after a few minutes, the train is checked down for a few seconds before accelerating again. This has happened on every train I've been on for a while now. As it seems to be on the approach to the first signal controlled by the West Mids SC, my theory FWIW is that the signal shows a restrictive aspect until it detects that the train is entering it's control area, when it then changes.
It could just be a TSR of course, however, this change seemed to happen after the resignalling and the dip in speed isn't consistent with that. it's more of a power off, then a few seconds and power on. Imagine the speed graph being more like a sign wave than a "down, along and up" shape which one would expect with a TSR. Also I haven't noticed it happening on the Down direction towards Shrewsbury, although of course the train is already slowing down from line speed at that point.

An info would be appreciated.

 

[Arriva 175]

I believe it is no more than a running break test. Crews change over at Shrewsbury.

 

[lammergeier]

Probably a running brake test after a crew change or after the driver has changed ends (they have to do another one from the new cab.)

 

[Bertiethebobby]

Ah, I hadn't thought of that.
It would certainly explain the dip in speed, I have noticed a slight dab on the brakes occasionally but most times not. How much braking constitutes a brake test, just enough to see the needle move but not enough to feel as a pax?

 

[TheEdge]

Not sure if it's a set thing, but for my TOC a RBT is a drop of 10mph using step 1-2-1

 

[lammergeier]

It's company specific, some require a 5 mph reduction, some 10.

 

[daikilo]

Whilst I cannot confirm that a brake test is the reason, it cetainly makes sense given that the platform loop at Wellington has a 15mph lead and approach control.

 

[craigybagel]

Almost all services leaving Shrewsbury for Birmingham will have at least one of the following - a change of direction, a change of driver or a change of formation (like a 2nd unit being attached). Any one of those require a running break test.

 

[Bertiethebobby]

Thanks guys, an RBT does seem like the most plausible explanation. I don't think I've noticed it at other stations but maybe I wouldn't have if the train were still negotiating it's way out of a large station, say Brum or Euston.
This just seemed strange as once past Abbey Foregate the driver throttles up but after a couple of minutes there's this short dip in speed the accelerating again.
My signalman's brain interpreted this as someone forgetting to clear the signal, but every time makes this seem unlikely. And even less so now I've had this explanation!

 

[XDM]

I am told that not every TOC demands a running brake test. And one TOC I know only specifies it if it is below freezing.