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Roads to Nowhere

RAC call for new roads rests on shaky foundations

Sian Berry's picture

21 November: It seems the RAC Foundation needs reminding that population and traffic growth are no longer joined at the hip.

The charity issued a stark warning today of a future of inexorably rising traffic growth in the UK, and slammed the government for not explaining "what plans they have to cope with the bleak picture painted by their own numbers."

Their report, "Keeping the nation moving: time to face the facts" criticises the government for having a minimal road-building strategy that's incompatible with the DfT’s current set of traffic forecasts, which predict rising traffic year-on-year for decades. This is quite true, and I pointed out the flaw in these forecasts and the consequences for road scheme appraisal in a blog post last week. If the RAC Foundation is genuine in its call for these forecasts to be "publicly and quickly amended" if the DfT won’t stand by them, then I’d be quite happy to see that done.

But the focus of the report isn’t to challenge DfT traffic forecasts. Instead it aims to scare the government into backing the Foundation’s list of 96 road schemes. In doing this, it brings an even more blunt instrument to the table, by framing its warnings around population.

The report predicts that: "There will be at least four million more cars on the UK’s roads in the next twenty-five years as the population grows by more than ten million."

However, this ‘prediction’ is nothing more than taking today’s levels of car dependency and applying them to an increased population. And, importantly, it does not take account of the steady decoupling of population growth from traffic growth in recent years.

So, today, I thought I’d take a quick look at the actual facts and see if their case stands up. Taking two sets of figures, one from the Office for National Statistics on UK population, and the other from the DfT on traffic, I matched them up. This first chart shows changes in traffic and population compared with a 1993 baseline of 100, as used in the latest DfT traffic stats:

Population vs traffic 1993 to 2010

Here it’s already pretty clear that the growth in population and the growth in traffic are not related as closely as the RAC would like us to believe. And if we look in more detail at the most recent period – from 2000 to 2010 – the break between traffic and population becomes even more obvious:

Population vs traffic 2000  to 2010

In its report, the RAC Foundation highlights the last decade as being particularly bad for road building – with only an additional 1% of road miles added to the network, while "the British population grew by about 5% and total traffic rose by 6%".

However, the chart above clearly shows that this was a decade of two halves. Starting before the banking crisis in 2008, there is a rapid switch from rising traffic to the opposite trend, while the population curve grows steadily steeper as time moves on. By the end of the decade, population growth has actually outstripped car traffic growth by 1.4% (5.6% population growth vs 4.2% growth in car traffic from, 2000 to 2010).

With such a recent and sudden change, it is clear that everyone needs to be very careful about predicting the future of traffic in the UK. The current drop will be influenced by many different factors. Migration going mainly into urban areas, different attitudes of younger people towards cars, better public transport provision in the major cities, the cost of petrol and the recession probably all play their part. And how we influence future traffic may depend on whether we build on the positive reasons for this trend or build more roads.

But what these charts show most clearly is that, in these circumstances, simply taking 10 million new people and assuming current patterns of car use will continue for decades does not count as a robust prediction from the RAC Foundation, and should not be taken seriously.