When HS2 was first announced, many people assumed that trains were always good for the environment, and didn’t look closely at HS2 itself.
And in spite of many people’s assumption, HS2 will cause increased carbon emissions not just for a few years, but for decades, possibly centuries. Even HS2 Ltd’s own document on carbon admits that after the 60 year assessment period for the first six decades of operations, HS2 will cause increased carbon emissions. The thing is that most of the carbon costs are during construction: once Hs2 is built, this costs are fixed.
Even when HS2 Ltd looked at the second sixty years of operations – taking us from 2086 to 2145 – HS2 may still be causing increased carbon emissions.
Any savings will come from operating high speed trains, and HS2 compared the costs of running high speed trains to other current forms of transport. But this makes huge assumptions about war will happen in future: and HS2 couldn’t even anticipate the use of mobile devices on trains.
If you look backwards, to travel 60 years ago, you were still in the age of steam trains. Changing to diesel and electric trains had a profound effect on the environmental costs and benefits.
Look back another 60 years, and you are in the age of the horse, when newspapers were concerned with the environmental effects of the horse.
We don’t know what travel will look like in 60 years, let alone 120 years, so any claims that HS2 will be better than all the alternatives are unwise and unlikely to come to pass.