A few people have asked why the "new" platform 7 at Gatwick isn't level with the doors on the train in the pic and why we couldn't just build it higher. It's a sensible question and to save everyone getting a slightly different answer, here's why... /1
Very few mixed-use (freight and passenger) railways anywhere in the world have true level access to trains. As the owner of a legacy system dating back to the 1830s we're often in the position of having to make the most of a bad hand and our platforms heights are no different. /2
Over time we've alighted on a standard platform height of 915mm across the UK, with some room for variation. That standard is what all train providers work towards so all their stock (freight and passenger) will run past platforms without scraping them or worse. /3
Stationary or low-speed trains don't wiggle about much so this picture gives the impression we could add a few inches to the platform to match the doorsteps and all will be well, especially as it's straight. /4 Image
...but a moving train - and trains run through Gatwick at over 50mph - move around quite a lot and were the platform at the same height as the train doors, we'd need to move the track away from it to stop trains whacking it at speed. You'd still need a ramp to get on and off. /5
That's not even considering freight trains, of which there are quite a few on this line, which are of different sizes and heights, albeit all within a prescribed "envelope". Again, a higher platform would get struck by their wagons, and we would be in trouble. /6
While this platform is straight, many are not, and on those platforms a level height would require the track to be even further away, as the corners of train carriages swing out on curves. Added together those are the "kinetic envelope"... /7
... which means we have to design the railway around a bigger size (or envelope) than a stationary train in a picture would suggest. The reason for sticking to a standardised height is that we know that trains will run past platforms curved or otherwise, with no problems /8
What can be done though? Well, multiple train types use Gatwick's platforms so a standard height is sensible, but on platforms at stations only served by @TLRailUK class 700 trains, we've built "humps" that match their accessible coaches. /9
That allows for level boarding in those particular coaches, but at stations with multiple train types and freight, we need still need to use ramps. There is another alternative, which is to lower the doors on trains and build ramps into the trains themselves. /10
That is already happening on some train fleets, and new railways - which only have a single type of train ever using their platforms - can have higher standard platform heights. That's the case on some Tube lines, for instance. /11
So to conclude, we realise it was a more complicated answer than many of you hoped for, and we also know how important it is for passengers with wheelchairs/buggies and luggage to have simple, easy journeys. /12
...which is why Gatwick is being rebuilt with more lifts and wider platforms, and why our colleagues at stations are so important to making sure all our customers are safe and happy on their journeys. We hope that explains it. /Ends

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More from @NetworkRailSE

2 Nov
It was great for us, @CostainGroup, @Gatwick_Airport + @GatwickExpress to welcome @HenrySmithUK to #Gatwick today, to see how we're building for a brighter future with @transportgovuk . Read more about the £150m development here ⬇️ /1
networkrailmediacentre.co.uk/news/construct… Image
This blue sky will be filled with a new overhead concourse, stretching across platforms 7-5, and platforms 5-6 (currently out of use) will be rebuilt much wider, with new escalators and lifts to make travelling through Gatwick's station much easier for everyone. /2 Image
This former escalator from platforms 5+6 is no more, and the footbridge is also set for demolition - a tough task with trains running on the Brighton Main Line underneath! /3 Image
Read 5 tweets
24 Aug
UPDATE: You'll have seen plenty of coverage of this picture today and yesterday, showing the derailed train at #Tonbridge. Here's a brief overview of where we are and what we are doing, also why @Se_Railway are affected even though it's not their train... /1
This picture shows clearly the cables cut when the low-speed derailment happened yesterday, in sidings off the line to Redhill. The cut cables mean those sidings are completely "dead" and trains can't move. That includes @Se_Railway trains, which are trapped without power. /2
Our colleagues @Se_Railway are running as many trains as they can on the Tonbridge/Charing Cross services but there will be some cancellations as some of those trains are usually formed of stock trapped in the sidings today. Please check with them for travel details /3
Read 9 tweets
29 Jul
We’ve been filling your timelines with #HitherGreen content this week to show what we’ve been doing while no @Se_Railway trains are running in the area, and now it’s time for a serious #geekthread! What is signalling and why are we replacing it? /1
Signalling allows for the safe movement of trains, making sure they don’t hit each other, and making sure they’re literally on the right tracks. A train travelling at 90mph will take a mile or so to stop, so these are much more than traffic lights. /2
Our 92 signals in #HitherGreen are now mostly 4-aspect (colour) LEDs. The reason for 4 aspects is to give trains time to slow down. These go red, yellow, double yellow, green. Red means STOP, yellow means “caution, the next signal is red”. /3
Read 23 tweets
22 Jul
If you enjoyed our #geekthread on the upcoming #HitherGreen engineering work, which marks the end of 46-years of signalling from this brutalist building at London Bridge, you might enjoy this mini-thread... /1 Image
Among the sadness from everyone who has worked at this signalling centre is the knowledge that the railway is always evolving, and when London bridge box opened it took with it some smaller boxes, including the busiest in the country...
Borough Market Jn (pic @RailwayMuseum ). /2 Image
Perched high on the viaduct above the market, it signalled 100 trains per hour at the busiest times, using an old lever frame (pictured), and was a two-man job. Amazingly, the box has been preserved @RailwayMuseum , which reopens to the public on 4 August. /3 Image
Read 6 tweets
13 Feb
Please get comfortable as this is a long thread from our MD John Halsall to explain what’s happened at #EastGrinstead and what we’re doing to get it fixed. Here goes…
We've had a landslip near East Grinstead station, so it’s not safe to run trains @SouthernRailUK @TLRailUK
We already had a smaller landslip at the same site on December 28 last year, however we were able to run trains safely by introducing a 20mph speed restriction. Since then we’ve been monitoring the embankment closely and designing options for a long-term fix.
However, the recent severe weather as a result of Storm Ciara and heavy rain overnight yesterday has beaten us to it, because the ground has started moving again and the embankment has got worse.
Read 14 tweets
9 Feb
⚠️ #StormCiara super-thread. We'll update this as the day goes on with incidents/advice affecting @Se_Railway / @SouthernRailUK + @TLRailUK until the winds die down.
This is the Chelsfield trampoline as it was at 7am today - it has since been removed!
@Se_Railway @SouthernRailUK @TLRailUK Ongoing incidents affecting @Se_Railway + #TLUpdates:
Power lines on track @ Chilham, line blocked between Canterbury + Ashford
Train struck tree @ Slade Green
Tree blocking London-bound line @ Falconwood
Tree down and hit by train Knockholt, line blocked coast-bound...
@Se_Railway @SouthernRailUK @TLRailUK ...
Debris on line @ Sutton - both lines blocked while we remove it.
Train struck tree @ Tadworth, blocking both lines to Tattenham Corner (affecting #SNUpdates)
Platforms 5+6 closed @ Gatwick for loose roof.
Tree down blocking lines @ Ashhurst station (picture below)...
Read 46 tweets

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