Trains pass through Boxhill & Westhumble slower southbound than northbound?

[317663]

BoxHill

I've been watching some videos of Boxhill station, including being there myself, and just wondered why trains passing through A LOT SLOWER (non-stopping) on the southbound (towards dorking) go a good 20mph slower, I'd say about 40mph, whilst northbound (towards Epsom) go through at about 60 ish. I know the line speed through boxhill is 75mph.

Is the slower southbound speed because of the signals, or is this an ACTUAL one-track-side speed restriction?

 

[tsr]

Linespeeds should normally be 75mph each way through Box Hill & Westhumble, subject to any restrictions. Southbound trains are most likely either slowing because of a Northbound train (probably a SWT/Southern service starting at Dorking) crossing the points from Dorking Platform 2 or 3 to the Up line ahead, meaning signal CA186 (the Down signal at Box Hill & W.) is at caution, protecting CBK3/4 signals just before said points; braking for the much more restrictive (15/30mph, depending on platform) speeds at Dorking; or running according to any prevailing leaf fall conditions.

 

[TDK]

I don't suppose it is anything to do with the gradients?

 

[tsr]

I don't suppose it is anything to do with the gradients?

The Up end of the station itself is roughly at the lowest point between the two gradients, so I think signalling and prevailing rail conditions are more likely to cause speeds to seem lower in the immediate station area. Obviously any compensation for the uphill gradient out of the station on the Down line could, if practical, be mitigated by the downhill approach to it, and any faster speeds possible.

 

[starlightEXPRESS]

Southbound trains are most likely either slowing because of a Northbound train (probably a SWT/Southern service starting at Dorking) crossing the points from Dorking Platform 2 or 3 to the Up line ahead, meaning signal CA186 (the Down signal at Box Hill & W.) is at caution, protecting CBK3/4 signals just before said points; braking for the much more restrictive (15/30mph, depending on platform) speeds at Dorking; or running according to any prevailing leaf fall conditions.

From my observations as a passenger, CA3/4 tends to be held at red until the down train has left Box Hill and Westhumble, which means that CA186 (at the south end of BXW rarely shows anything other than a single yellow or a red. In roughly twenty years, I've only seen CA186 with a green aspect once (and I think that was when an ECS GEx Class 460 was sent that way).