wfb: "Can it be shown that this spending makes any difference? "
Whilst I'm confident that spending money on infrastructure makes some difference, it probably requires much more significant expenditure to make a real and noticeable difference.
If we were spending the same proportion of our transport budget on cycling as, say the Germans or Swedes do (let's not even mention Denmark or Netherlands, too humiliating) then just maybe we might have a cycling culture explosion in Scotland.
As it is, even the miserly tokenism we do have is being abandoned in favour of trunk road and motorway expenditure. Where is the 'evidence' that these massively expensive projects will bring benefits? To whom and by how much?
The SNP have got some things right in a difficult public funding climate, but on transport it's clear that (whether the minister is plump, rakelike, a beanpole or a shortarse) the petro-economy is their priority. Which is frankly just 'business as usual' and very similar to what the Tories are doing down South.