Britain is max 200kph (125mph) currently although there is infrastructure designed for 225kph (140mph) on conventional lines though this is not permitted any more. It’s not correct to say that trains circulate at close to top speed a lot of the time as they share tracks with freight and commuter and there is a lot of congestion on uk lines. It’s not as bad as the US as commuter trains can also travel at 100mph and freight at 70-80mph. But it does prevent faster trains from travelling at 125mph for sustained periods. Also most routes were built in the mid 19th century and are not designed for sustained high speed running. If you look on openrailmap you’ll see there are occasional stretches of 125mph, longer stretches of 110mph but both are interspersed with 60-80mph here and there as the line threads its way round various hills that steam locomotives couldn’t cope with 175 years ago. So trains have to constantly decelerate and accelerate for curves and trains that stop more frequently. E.g the average speed of the fastest Glasgow to London train is about 90mph. British intercity trains are dogshit compared to France e.g the fastest Paris Bordeaux train at average 186mph is cheaper and more comfortable. Britain urgently needs more capacity and it might as well be high speed, but we’ve dropped the ball on that. Glasgow/Edinburgh-London should be 2-3 hours making it competitive with flying but it’s more like 4-5 hours, more expensive and as cramped as Ryanair but 6 times longer journey time.
> Britain is max 200kph (125mph) currently although there is infrastructure designed for 225kph (140mph) on conventional lines though this is not permitted any more. It’s not correct to say that trains circulate at close to top speed a lot of the time as they share tracks with freight and commuter and there is a lot of congestion on uk lines.
I was referring to Britain's adoption and pervasive use of its InterCity 125 trains.
The interesting aspect of the InterCity 125 was the fact that, instead of going with an optimized record breaking train, British Rail went the other way around and optimized their track layouts to allow an unimpressive train to achieve what was at the time unmatched commercial speeds.
No you’ve got it the wrong way round the Intercity 125 was an impressive feat of engineering designed very quickly as a temporary stopgap while lines were electrified and still holds the record for world’s fastest diesel train. It was a side project of the engineers that were designing the Advanced Passenger Train that was being developed at the time, which was supposed to be able to run at up to 150mph on conventional routes using tilting technology. The intercity 125 incorporated a lot of the lightweight construction research that was done for APT. Not much was done to the track to enable higher speed running, some resignalling and very very occasional route realignment for higher speeds. The intercity 125 achieved better times by being more lightweight and having faster acceleration than conventional locomotive hauled trains of the time, but it was only 15mph faster than the conventional trains. Most of Western Europe has standard lines with up to 125mph running, it is not uncommon. E.g a lot of the old non-tgv line between Paris and Bordeaux supports trains running at up to 200kph (125mph) Likewise 200kph running is common in Germany with conventional trains. The track in the UK was not special, quite the opposite as when the 125 was introduced we still had a lot of victorian style jointed rails that had been obsolete since the 1950’s. Britain was slow to upgrade to continuous welded rail, it wasn’t gone from all main lines until the 1990’s.
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