Don't know if we'll get any Bristolians on here complaining that the GWM is really the one that goes to Temple Meads, but I'm really thinking of the line that diverts to us in South Wales past Swindon (Wooton Basset funnily enough).

I've been reading up online quite a bit on it recently. Such information isn't necessarily 100% accurate but nonetheless several things have struck me. Firstly I believe the electrification is supposed to be complete by 2017 and 2018 for Swansea? It's been said this will reduce journey times from Paddington to Swansea by 20 minutes. You would assue that would mean perhaps 15 minutes from Cardiff to Paddington. Now currently the line speed is a maximum of 125mph. However my online reading suggested that once you get past Bristol that speed is only 75mph! So much for the Intercity 125 in Wales. This might suggest that the biggest opportunity for improving journey times would be within Wales?

Now I'm presuming the reduced journey times would be accounted for by the greater accelerating/decelerating qualities of electric trains. However the 125mph limit (which doesn't seem to apply in Wales!) isn't set in stone. The trains could well be capable of trvelling up to 140mph+ (actually as the current ones are) it's just a question of safety and I believe the quality of signalling. If this were possible might we see journey times to Paddington reduced to 100 minutes or less. The current time is funnily enough 125 minutes, although I notice at the moment the weekends are more like 150 minutes perhaps due to the work being done on the line.

Finally there is the issue of crossrail and the possible rail-link from Reading to Heathrow. Whether our trains would continue on their current line or we would have to change at Reading who knows. The posibility of a 90 minute train journey to Heathrow seems quite enticing. Of course if there ends up being an adventure on Boris Island and Heathrow turns into a giant housing estate it would rather pull the rug from under our feet.

I don't get it either. I thought the increase in journey times since the 1980s was due to track congestion, which presumably won't change after electrification.

I remember in the 1980s, there was a massive poster across Newport Station, with a picture of an Intercity 125, and the caption; "Newport to Paddington in 93 minutes".

After 30 years of "progress", the very best you can hope for is 110 minutes - over 18% longer, and that's only if it coincides with numerous optimal conditions, and various constellations come into alignment.

decreased times can only really come from decreased stops, its not going to happen, if anything we will get additional stops with didcot becoming more regular and adding 5 mins back in.
its a shame, but as with HS2, does 15 to 20 mins make any realistic difference?
On train services such as wirles, signals and power more appealing

Well they did claim that electrification would lead to shorter journey times. As for the number of stops, there's plenty of distance between Cardiff and Bridgend to attain top speed and yet apparently there's a 75mph speed limit. That makes sense when you consider that it's a 20 minute journey to go 20 miles.

if it all stays as it is Cardiff should get 15 mins quicker, but I think the case for didcot will be well made and will become a regular stop.
it will be a little bit, maybe ten mins for Cardiff.
not being negative, lots of plus sides for electrification, but re configuring reading and sorting the severn tunnel properly pretty much deliver the same savings on their own.

less sure on the welsh side, thionk there is an issue with the small stations on the line and going through them at platform line at full tilt, will ask a rail friend.

Don't they all stop at Didcot nowadays? I thought that was one reason why it was over 2 hours nowadays. It does mean you can get a good change for Oxford of course.

I'd like to see how they handle the severn tunnel electrification-wise which is a further complication to what is already problematic. I've noticed myself how trains often seem to slow down at stations even when they don't stop, Chepstow is a good example of this whenever I go to Birmingham.

I wonder if the problem with speed is more about other trains on the line. It's all well and good having one that can go at 125mph, but if the one in front only does 100mph, then you have a problem.

Given the amount of money being spent on Reading station it better all be sorted.