Why 85mph?

[southern442]

When I last went down that line I don't remember seeing anything better than 70, though I'll take your word for it

That is probably because most of the down line between Sanderstead and Oxted is actually 70, it is 85 mph on the up side (this is info I have from a driver). Hurst Green-Lingfield is also 85.

 

[brad465]

I see, do you know what the up side has that the down side doesn't to get the 15mph higher value?

 

[bramling]

I see, do you know what the up side has that the down side doesn't to get the 15mph higher value?

I suspect almost certainly due to gradient in this case. It's an uphill run from South Croydon all the way to Oxted Tunnel (1 in 100 springs to mind), so the chances of any down trains exceeding 70 mph were probably minimal at the time the limits came into being - especially as most non-stop trains were/are formed of diesels to Uckfield, the classes 205 and 207 having a maximum speed of 75 mph anyway, not that they could reach much above 50 mph on this section in reality, and I suspect a Turbostar doesn't do a great deal better.

Today perhaps an Electrostar on a non-stop down run might be able to exceed 70, but I suspect not worth the effort given almost every electric service is all stations on this line.

By contrast, the downhill gradient on the up line means higher speeds are more readily attainable, so presumably at the time a case was able to be made for increasing the speed.

This is only conjecture, but it does provide a possible explanation.

 

[70014IronDuke]

Surely that could be argued until the days of OTMR and TPWS as speed limits would have been difficult to enforce?

That is actually a very good point. By the late 60s (or early 70s at the latest) drivers talked of the risk of "speed guns" (presumably like police roadside speed checks) being used trackside - but i never actually met a driver who had been pulled up for overspeeding. Or at least I can't remember so. (And I know from experience there were definitely drivers willing to 'give it a go' if they were running late.)

But I don't know if they had the technology before about 1965 - so what did they do then?

And, in truth, if someone went through, say, Wolverton at 85 instead of 75 (or whatever it was), and speedometers were not fitted to the locomotive, what would the unions say about this? enough for a new thread all to itself!

 

[furnessvale]

But I don't know if they had the technology before about 1965 - so what did they do then?

In the mid 1960s we had a treadle system at the District Engineers office which could be fitted to the track to measure speeds.

One was fitted at Lancaster because of complaints of speeding. It was getting speeds of 130mph+! Was Mallard under threat? NO. The local shunt engine was going back and forth over the treadles upsetting the readings.

 

[Donny Dave]

I see, do you know what the up side has that the down side doesn't to get the 15mph higher value?

I've been wondering about this as well, as there is a section between Scunthorpe and Doncaster like this. From Doncaster, it's 25mph over Marshgate Jn, then 80mph until Hatfield and Stainforth station. in the opposite direction though, it's 85mph from Hatfield and Stainforth, dropping to 60mph at Bentley Jn, before dropping again to 25mph for Marshgate Jn.

 

[bramling]

That is actually a very good point. By the late 60s (or early 70s at the latest) drivers talked of the risk of "speed guns" (presumably like police roadside speed checks) being used trackside - but i never actually met a driver who had been pulled up for overspeeding. Or at least I can't remember so. (And I know from experience there were definitely drivers willing to 'give it a go' if they were running late.)

But I don't know if they had the technology before about 1965 - so what did they do then?

And, in truth, if someone went through, say, Wolverton at 85 instead of 75 (or whatever it was), and speedometers were not fitted to the locomotive, what would the unions say about this? enough for a new thread all to itself!

Speed guns have been used on LU since the 1980s. The agreement is that a warning poster is displayed in the notice case, although the poster doesn't give the location or time. Any infringements *will* be followed up. Occasionally an infringement might be picked up via a train download, for example in response to a passenger complaint.

Speeding certainly happened on the mainline up until OTMR. I can think of many journeys on suburban services out of King's Cross even up until the 1990s where 75 mph was quite evidently being exceeded on the slow lines. Never happens today though.