And sitting alone in a tin box weighing a ton, permanently removing scarce, dwindling, hydrocarbon stocks from the planetary store whilst simultaneously inserting into the atmosphere gases which contribute to planetary warming is preferred? Properly managed, rail is an excellent transportation mode. Go to Japan to see how it can be used - or if that is too far then France will also be instructive.
And if you are against a third runway being built at Heathrow, you have a high speed connection which goes quite close to four other runways - two at Manchester and one each at Birmingham and East Midlands.
... And as for the land that is being used to beuild this railway ... Heathrow takes up more space than the East Coast main Line.