There's an interesting article about "Airtrack" in RAIL magazine No. 673 by Christian Wolmar, one of Britain's leading rail journalists. "Airtrack" is the name given to the scheme to provide a rail link to Heathrow Airport from the southern side. It would run from a junction with the existing rail route between Staines and Chertsey into the airport.
The link is only 4 kms long and it uses an existing railway route for part of its length but the cost is estimated at £673million. Why so expensive? That's over £168million a kilometre - for a bit of tunnel and the rebuilding of an existing route?
His article can be read online here: How Airtrack was derailed.
There's a few things in it that are quite controversial. The first is the cost, as I mentioned, but another is the problem of level crossings. There are a lot of them - 15 all together - and they cover the three routes that would be used by the new service, from Waterloo, Reading and Guildford. Christian writes that he was surprised when Phillip Hammond, the Secretary of State for Transport, "had a rant about level crossings". I'm not. They are a nuisance and dangerous because they cause frustration when car drivers have to wait long periods with nothing apparently happening, so drivers take chances with them, risking their own lives and those of train crew and passengers. It's time there was a programme to remove them at the earliest opportunity. It's expensive but worth doing. This route would have been a good place to start.