IT is time to take the party politics out of the debate over a new transport link between Glasgow and its airport.

For too long discussions of the original Glasgow Airport Rail Link (GARL) plan and subsequent Glasgow Airport Access Project (GAAP) have been as dogged by political rivalries as they are by ugly acronyms.

The report today from transport consultants Jacobs on the latter scheme is unequivocal. GAAP as envisaged is not a realistic option, its business case fatally flawed on a number of levels.

Passenger forecasts are not robust, it argues. This is not surprising. Many air travellers, particularly in the Greater Glasgow area, and particularly regular travellers, would not use a rail link. Private car use to and from the airport is high, because most of those using the airport are not travelling to or from the city centre. For those who do there is a reliable, quick and affordable bus service, which any rail link might struggle to rival for cost or speed.

Station capacity is limited and any rail-based service would hold up other key developments such as electrification of the Glasgow to East Kilbride route. Rail capacity is limited and GAAP would see “service degradation” on the important Glasgow-Paisley route – one of the most pressured stretches of rail in Scotland.

For those who doubt the importance of this, Jacobs say the economic cost of worsened journey times between Ayrshire, Inverclyde and Glasgow would be £4.1m a year. The report doubts whether any economic benefit would outweigh this. GAAP’s business case is not sufficiently robust to be sure. Overall, the audit concludes, proponents of GAAP may have overestimated the benefits and underestimated the costs of such a link.

Susan Aitken, chair of the Glasgow City Region Cabinet, says partners are committed to a surface access project to and from the airport – with funding from the City Deal. So what is the best way forward?

GAAP was a cheaper alternative to the GARL scheme, using trams on the train tracks to cut the cost. But as Jacobs’ report shows it is relying on rail at all that made both plans problematic. Apart from the capacity issues, it limits the possible stops – GAAP would not have called anywhere between Glasgow and Paisley.

A solution – perhaps more costly, but greatly preferable – would be an on-road tram scheme. Some will point to Edinburgh’s tram fiasco as a warning but the errors made in that scheme are educational as well as salutary.

Like the bus it would enable passengers to reach many parts of the city. It could call at the Queen Elizabeth University Hospital, helping solve that facility’s dire public transport deficit. It could serve Renfrew, the biggest town in the country without a station. It might link to Govan and Braehead Shopping Centre, providing much clearer economic and social benefits than any rail link.

Partner councils, Network Rail and Transport Scotland are to meet to discuss the project in light of this new report. They should pursue all lines of inquiry.