THE “Bain Principle” is one of Labour’s biggest weaknesses in Scotland. The SNP has wisely avoided simply rejecting things that others have thought of first. There are ineffective transport systems and effective ones, expensive ones and cheap ones. I would assert it is difficult to find an example of “cheap and effective” – hence the problem for vote-hungry politicians of all hues.

The new Forth Crossing is a good example of something that cost a lot of money, took political determination, but was worth it.

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The question of access to Glasgow Airport cannot be decided by the priority needs of Paisley’s commuters. It serves Scotland – a population north of five million – while Paisley has about 100,000.

Neither can it be expected for air travellers to lug cases across the airport, onto a diddy travel pod, off it, up into a railway station, onto a crowded commuter train, into Glasgow Central Station, and possibly down stairs and escalators for Lanarkshire trains, or cross the city to another railway station for onward travel.

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Part of the problem is that previous wisdom led to decisions to remove rather than replace a four-track second bridge across the Clyde into Central, and to reduce from four to two the number of tracks from the Paisley direction from Shields Road into the Central Station approaches. These were justified by cost savings, signalling improvements and traffic flows at the time. This is why access is constricted now, and amelioration will be expensive, eg a two-track new bridge to ease traffic access from the east into Central, freeing capacity from the west.

Putting trams onto the existing train lines from the west, with different acceleration and braking regimes, different current systems and signalling, was an excellent example of unicorn thinking. Trams are not simply trains, only cheaper, just because both use rails. Both have virtues and problems, and neither come cheap if they are to be effective.

If the answer is a rail line, it will be expensive but effective, particularly if it offers an alternative onward travel route as well as Central Station. The 40-year campaign for Glasgow Crossrail would offer direct trains via Glasgow Saltmarket, to Airdrie, West Lothian, Edinburgh, or Cumbernauld and Stirling/Edinburgh, or direct access to Queen Street for the Scottish intercity network. Incidentally, access to Paisley would improve.

If the answer is a tram, it needs a limited-stop route from the airport to the city centre area, possibly along the M8 via Braehead – otherwise it is too slow, like the Edinburgh Tram. The problem then is getting access across the Clyde into and around the city centre, mixing with road traffic on the surface. Underground construction will be expensive and complicated, given three existing underground rail systems – Edinburgh’s construction problem on steroids.

It might be possible to go north across the Clyde from the airport by rail to the Queen Street low-level line, or by tram to the Clyde Expressway. I can’t see either being cheap, needing a new bridge or tunnel – although both would solve Paisley’s possible conflicting commuter issue, and give wider access to the airport.

I didn’t join the SNP until after 2014 – although voting for them – as I viewed their transport policy as short-sighted. The two proposed airport rail links were possibly visionary, certainly expensive, but I favoured both. The SNP did not. In the end Labour helped force through the Edinburgh Trams – the least useful of the three schemes they had favoured – just to embarrass the SNP.

I’m still not convinced the SNP have good long-term policy, although the Forth Crossing was done well. Transport spending won’t pay off in time for the next election, which is why all political parties delay big decisions. They never get cheaper, you just miss out on the benefits for longer.

If Glasgow Airport is to have fast and convenient public transport links with Glasgow city centre and the rest of Scotland, and reduce dependence on roads, it will take several years and a lot of money. Bite the bullet, and maybe start now?

Dave Robb