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Comment by dcel | Hacker News Reader

Max line speed of HS2 is 360km/h, with provision for 400 in some sections in future. This is entirely in line with many other modern HS lines. China’s been running regular 360km/h services for years.

This is a project with a 200+ year shelf life. Designing to 300 or less would have been short sighted, and many of the changes to accommodate such high speeds actually reduce costs in the long term (slab track, headroom to catch up delayed services, ability for one trainset to operate more services per day etc).

The cost overruns of HS2 are primarily from plain old poor project management, complex planning law and constant political meddling, not engineering decisions.

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China has run at 360kmh before, but last I checked they mostly run slower.

Air resistance is a killer as you go faster. So for trains 300 is usually about the best compromise between energy use and speed. If you want to go faster a jet at altitude is going to be much faster at a better fuel efficiency. High speeds make sense for long distances.

This is a project designed to last for centuries. We’re not even fossil free yet and already seeing days of negative electricity cost thanks to renewables. In 50 years the extra energy cost is going to be a rounding error. Locking ourselves into 300km/h forever to save a relatively small sum is unfathomably short sighted.

> Max line speed of HS2 is 360km/h, with provision for 400 in some sections in future.

That's already been reduced to 320 km/h under this year's "HS2 reset". Which I imagine in reality will be 300 km/h normally at most, with even lower speeds seen day to day

Interestingly the written report to the government stated "However, no railway in the UK, or globally, is currently engineered for 360 kph". Are you incorrect or did they forget to include China in their research?

Anyway, I thought these were last decade's talking points? I thought it was all about capacity now, not speed? Except I thought there were also rumblings about reducing capacity from the previous announcements? Hard to keep up...!

The messaging, in general, has been abysmal. But capacity and speed are not separate concerns. Consistently high average speeds increase capacity - I wish this had been actually communicated.

> The messaging, in general, has been abysmal

Indeed, which has eroded trust. That along with huge cost revisions, you can see why some people are incredibly pessimistic about the entire project

It was all planned lies: high speed rail is sexy. It sold the project.

> Consistently high average speeds increase capacity - I wish this had been actually communicated.

Show us the numbers then ;) And the cost benefit of higher speed vs longer stations and trains

One of the drivers of cost has been the high speed part. It meant the route needed to be straight which meant more tunnelling to avoid certain areas. Lower speed track would have allowed them to route around problem areas.

High speed rail does not need to be straight! You can get away with 6km radii at 360km/h on dedicated passenger lines. The high power output of the EMUs they’ve selected and all new OHLE power supplies mean that trains can accelerate and decelerate much more aggressively than on legacy mixed use lines like the WCML, allowing smaller radii in practice with short slower sections. It’s a myth that HS2 is expensive because it had to be straight.

The vast majority of the tunnelling for HS2 has been either to get in and out of dense urban areas without too much demolition, or to reduce the political cost of driving a building site through Tory heartlands (Chilterns AONB).

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