The Anonymous Widower

Thoughts On Train Times Between London Paddington And Cardiff Central

I went to Cardiff from Paddington on Tuesday.

These were the journey details.

  • Distance – Paddington and Cardiff – 145.1 miles
  • Time – Paddington and Cardiff – 110 minutes – 79.1 mph
  • Time – Cardiff and Paddington- 114 minutes – 76.4 mph

There were four stops. Each seemed to take between two and three minutes.

I do feel though, that the trains are still running to a timetable, that could be run by an InterCity 125.

I watched the Speedview app on my phone for a lot of both journeys.

  • There was quite an amount of 125 mph running on the route.
  • Some stretches of the route seemed to be run at a line speed of around 90 mph.
  • The Severn Tunnel appears to have a 90 mph speed.
  • Coming back to London the train ran at 125 mph until the Wharncliffe Viaduct.

These are my thoughts.

Under Two Hour Service

The current service is under two hours, which is probably a good start.

Improving The Current Service

It does strike me that the current timetable doesn’t take full advantage of the performance of the new Hitachi Class 80x trains.

  • Could a minute be saved at each of the four stops?
  • Could more 125 mph running be introduced?
  • Could the trains go faster through the Severn Tunnel?
  • If two trains per hour (tph) were to be restored, would that allow a more efficient stopping pattern?
  • The route has at least four tracks between Paddington and Didcot Parkway and the Severn Tunnel and Cardiff.

I would reckon that times of between one hour and forty minutes and one hour and forty-five minutes are possible.

These times correspond to average speeds of between 87 and 83 mph.

Application of In-Cab Digital Signalling

Currently, a typical train leaving Paddington completes the 45.7 miles between Hanwell and Didcot Parkway with a stop at Reading in 28 minutes, which is an average speed of 97.9 mph.

This busy section of the route is surely an obvious one for In-cab digital signalling., which would allow speeds of up to 140 mph.

  • Services join and leave the route on branches to Bedwyn, Heathrow, Oxford and Taunton.
  • The Heathrow services are run by 110 mph Class 387 trains.
  • There are slow lines for local services and freight trains.

If an average speed of 125 mph could be attained between Hanwell and Didcot Parkway, this would save six minutes on the time.

Would any extra savings be possible on other sections of the route, by using in-cab digital signalling?

I suspect on the busy section between Bristol Parkway and Cardiff Central stations several minutes could be saved.

Would A Ninety Minute Time Between Paddington And Cardiff Be Possible?

To handle the 145.1 miles between Paddington and Cardiff Central would require an average speed including four stops of 96.7 mph.

This average speed is in line with the current time between Hanwell and Didcot Parkway with a stop at Reading, so I suspect that with improvements to the timetable, that a ninety minute service between Paddington and Cardiff Central is possible.

It may or may not need in-cab digital signalling.

My Control Engineer’s nose says that this signalling upgrade will be needed.

Would A Sixty Minute Time Between Paddington And Cardiff Be Possible?

A journey time of an hour between Paddington and Cardiff Central would surely be the dream of all politicians the Great Western Railway and many of those involved with trains.

To handle the 145.1 miles between Paddington and Cardiff Central would require an average speed including four stops of 145.1 mph.

It would probably be difficult to maintain a speed a few mph above the trains current maximum speed for an hour.

  • How many minutes would be saved with perhaps a single intermediate stop at Bristol Parkway station?
  • Perhaps the Cardiff service could be two tph in ninety minutes and one tph in sixty minutes.
  • Full in-cab digital signalling would certainly be needed.
  • Faster trains with a maximum speed of up to 155-160 mph would certainly be needed.
  • There may be a need for some extra tracks in some places on the route.

A journey time of an hour will be a few years coming, but I feel it is an achievable objective.

The Extended Route To Swansea

Cardiff Central and Swansea is a distance of 45.7 miles

A typical service takes 55 minutes with three stops, at an average speed of 49.8 mph.

This would be an ideal route for a Hitachi Intercity Tri-Mode Battery Train, which is described in this Hitachi infographic.

It would probably be needed to be charged at Swansea station, to both enable return to Cardiff Central or extend the service to the West of Swansea.


Big improvements in journey times between Paddington and Cardiff Central are possible.


June 10, 2021 - Posted by | Transport/Travel | , , , , , , , ,


  1. Hi, yes one hour is possible, but, The Severn Tunnel has always been a wet tunnel prone to leaks. There is also no way of compensating for pressure change as faster trains approach each other. Definately an area to explore. In steam days it had a 60mph limit, and in those days trains were prone to stalling on the steep gradients climbimg out. Not so much a problem with 8000HP electric units. I would suggest another potential ares to visit is what happens if a train leaves the rails? There are no escape tunnels, or space to extract people, or rescue teams, in fact I have never heard of any scheme that allows for emergencies in long tunnels. There was a train that stalled in Italy in 1944 in a long tunnel The train crew under toxic fumes, were unaware the train had stalled, and the train was only apparently discovered, engines still slipping, by accident. Six hundred people were thought to have died in the train by asphyxiation.

    Comment by jagracer | June 10, 2021 | Reply

  2. Could the tunnel evacuation problem be helped by using two five-car trains? One would evacuate to Wales and the other to England.

    Fred Snow’s plan of a Severn Barrage is looking better. This would have had a rail route and a motorway on the barrage over the estuary.

    Comment by AnonW | June 10, 2021 | Reply

    • Two five car trains is an idea. On You Tube there is a report of the high spead train in Germany throwing a wheel tyre at speed. Horrendous situation, and the result concertinered the carriages. Imagine that happening at 100 mph in a tunnel. A once in 100 years episode, but maintenance and NDT inspection is where the Inquest said the fault lay.

      Comment by jagracer | June 10, 2021 | Reply

  3. BR used to have one or two trains that did Parkway in just shy of 60mins so sub 100mins to Cardiff should be more than possible by just tweaking up timings. Cl8xx are already on a 23m timing to Reading yet have a lower average speed to Swindon where the line speed is largely 125 all the way. There appears to have been no line speed improvements west of Parkway but the 800’s clearly have better acceleration under the wires than a HST does.

    Comment by Nicholas Lewis | June 10, 2021 | Reply

    • Thanks!

      Probably confirms my view, that the timetable isn’t up to the Class 800s yet!

      I do think, though that we’ll see very fast speeds between Paddington and Reading, as streams of 140 mph race to and from London.

      Comment by AnonW | June 11, 2021 | Reply

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