The new trams proposed for Edinburgh were supposed to reduce congestion in the city and provide a greener transport system in the city, but how green will they be, assuming that they do start running sometime?
A useful measure of a scheme’s environmental credentials are its embodied energy or embodied carbon: that is the amount of carbon emissions required in its construction. This normally consists of the carbon cost of producing the materials, for example cement production for concrete is highly energy intensive, as is steel production. This embodied energy can then be offset against carbon emissions saved to give a payback period – the period over which the scheme operates before becoming carbon neutral and after which there is a net carbon saving. For example, the carbon cost of constructing a wind farm can be repaid in around six months of operation.
In the case of Edinburgh’s trams, the embodied carbon would include not only the carbon from the materials and construction processes, but also the increase in carbon emissions arising from greater congestion in the city during the prolonged construction period. And the longer it takes to complete the higher this total will become. Once the tram is operational, this embodied carbon would be offset against reductions in emissions resulting from less congestion and more people using the trams rather than cars (again assuming they do and it is not only bus commuters who move to the tram, with a lower reduction in emissions).
It is difficult to enumerate all of these factors but my guess is that we would be looking at decades rather than years before the tram becomes carbon neutral, if ever.
With this in mind, and the fact that construction is currently stalled and is facing a funding shortfall, is there any point in continuing with the project?
Tavish Scott, the Transport Minister at the time of the Trams Bill going through parliament has ruled out further funding from the Scottish Government, the SNP have never fully supported the scheme, the conservatives won’t pay more and Labour (including Iain Gray, Transport Minister at the scheme’s inception) are keeping quiet.
It is not rational to pay out lots more money for something that isn’t fit for purpose, even though we have already spent vast sums, however the politicians won’t see it that way.