I have heard some nonsense about the M74 extension in the past, but my moral compass went haywire when I read in David Leask's article (December 10) that one of its backers thought that choosing between the half-billion-pound stretch of motorway or the Commonwealth Games was like being forced to choose between one's children.

There are many cases in which short-term economic benefit (however narrowly defined) is the only argument made in favour of a development while social and environmental considerations are cast aside. Typically, we are told to "strike a balance" between these factors, which is code for ignoring anything which ministers think won't boost GDP growth. "Think of the jobs", we are told, as ministers approve the new runway at Heathrow, or capitulate to ultimatums from arrogant billionaires who can't be doing with boring old democratic planning processes.

But in the case of the M74 extension the alleged benefits crumble so quickly under scrutiny that the plaintive cry of "One month to save the M74" cannot be taken seriously. The Herald's own article points out that it will not create jobs, merely move them around the country. It will certainly move more traffic around, but as research shows, this is self-defeating as traffic expands to fill the space available.

Your description of the problems with the Kingston Bridge is a perfect example. Built to cope with 20,000 vehicles daily and now carrying nine times that number, it's a clear demonstration that congestion isn't a function of "not enough road", but one of "too much traffic". Even without the new imperatives of climate change and peak oil, how long can this go on? Relentless increases in road traffic will leave this latest project as worthless as every previous predict-and-provide fallacy.

What SNP ministers - just like their predecessors - are wasting £500m on is five miles of road, hoping it'll shave a few minutes off car journeys, while public transport projects sit on the shelf waiting for political backing, and all this in a city where most citizens don't have access to a car. Even if you do "strike a balance" and ignore the deaths already being caused by climate change, this is a project that barely made sense in the middle of the twentieth century. It has absolutely nothing to offer Glasgow to prepare us for the reality of the 21st.

Patrick Harvie MSP, Scottish Green Party, Scottish Parliament, Edinburgh.