[jnty]

And after subsidising bus travel for 20 years we are left with nothing - other than, probably, an expectation to fund for the next 20 years too.

After HS2 is built we have an extrememly valuable asset which will generate returns for years to come.

Capital and current spending are very different, and it's quite unhelpful to compare the two.

[mantap]

Comparing the two is exactly the role of governments (and by extension, us as their supervisors) as there are only finite resources to allocate.

I don't think it's quite true to say that after 20 years we would be left with nothing. If it encourages more people to take the bus instead of driving then it would decrease traffic and pollution. Although in cases where buses are already in demand, adding new routes or increasing bus frequency on existing routes would be a better use of money.

[jnty]

But it would only decrease traffic and pollution for the duration of the spend. Once it's over, those benefits stop and there is nothing left beyond the lingering effects of the intervention.

It's actually worse than that, because you've essentially taken out an unsecured loan of £100bn and spent it on something which neither increases ongoing tax revenue or asset value, so you now have to cut other spending to pay it off. Which is why governments and businesses separate capital expenditure (building things) from current expenditure (doing things) very carefully.