So Scotland’s transport minister has given his backing to the Glasgow Airport Access Project or GAAP. Well, kinda.

Humza Yousaf is, he has told Holyrood Magazine, committed to the scheme. Or, rather, if you read his words carefully, he is a committed to a scheme.

That is no minor nuance. Mr Yousaf is not so much saying “Mind the GAAP “ as “Mind a GAAP.”

Because the very latest concept of the transit link to Abbotsinch is stopped dead in its tracks.

Council transport planners in Glasgow and Renfrewshire had reckoned they could run trams along the railway from Central Station to Paisley, one of the most clogged lines in Scotland.

These light vehicles would then run on to their own tramway to the airport. The Government’s Transport Scotland quango asked some experts, consultants from Jacobs to look at this. Their verdict? Such a scheme, at a pricetag of £144m, would not just be bad value for money, it would do more economic harm than good.

Sure, Jacobs were not quite so blunt as that summary in their lengthy technical report. But that is the thrust of their findings.

Their logic is straightforward: trams on a direct route from the airport to the city centre would not be very popular. For many passengers the existing bus would be quicker. And most people who travel to the airport regularly - either for work or to catch a plane - don’t live in the city centre. They would still go by car.

Do you want trams carrying very few people delaying trains with hundreds of commuters on board? Probably not. Do you want them taking up sought-after platform slots at Central Station? No. That could prevent key economically vital improvements to the rail network, such as electrifying services to East Kilbride.

Jacobs estimated the economic cost of slower services between Glasgow and Ayrshire and Inverclyde would run in to the millions. And council officials, they said, had not even considered this.

There were those in Clydeside local government who thought the Jacobs report, as damning as it is, would turn in to a pretext to park a rail link up a siding for years.

After, all a previous even more expensive rail link scheme had been promoted by Labour and knocked back by the SNP. Thus even a normally pointy-headed transit issue became weaponised in Scotland’s tribal constitutional politics.

Mr Yousaf’s comments - and similar remarks by the SNP leader of Glasgow City Council, Susan Aitken - suggests a truce is in the air. Labour’s former rail minister, Tom Harris, this weekend also cast huge doubts on the viability of the current scheme. A consensus is quietly emerging that a better option could be worked out.

There is an edge to Mr Yousaf’s remarks, however. GAAP is funded by the City Deal, a pot of cash from both London and Edinburgh. The transport minister suggests there will be no extra money. This raise another issue, if councils were to go ahead with the tram train scheme Jacobs trashes - and it, as expected flopped - who would pick up the the bill? Local authorities. That is a risk they will not want to take.