Discussing the Glasgow Airport Rail Link on Facebook recently, someone suggested that the route of the old Paisley and Renfrew Railway could be used. (https://www.railscot.co.uk/Paisley_and_Renfrew_Railway/index.php) This would be far easier to build than the original design incorporating an expensive viaduct over the M8. A smaller bridge over the white cart water would be needed and possible relocation of the sewage farm and/or some of the buildings on the airport side of the river (depending on how the line was routed). The disadvantage of this route would be the lack of interchange at Paisley Gilmour Street (passengers from Ayrshire and the west would have to change at Hillington West).
I was then informed that this route was put forward, only to be rejected by the council (was the lack of interchange at Gilmour Street the reason?)
How open are the council, government and airport to using this route for a heavy rail line? Could this be pushed as an alternative to the proposed "tram-trains"?