An article published in the Guardian (online) on Christmas Day suggests that Government proposals to increase the motorway speed limit to 80mph ‘would be expected to cause a 20%-plus increase in deaths’.
The Guardian says the calculation is based on the statistical model the DfT will use to assess the implications of the change. It also says that ‘road safety experts from Europe and the US are warning the DfT that while motorways remain significantly safer than other road types they are also especially susceptible to speed limit changes’.
Using the widely accepted ‘power model’, drawn up by the academic Rune Elvik from Norway’s Institute of Transport Economics, an increase in average traffic speeds of just 3mph – a typical change for a 10mph rise – would be expected to cause more than 25 extra deaths a year on motorways and more than 100 serious injuries.
Rune Elvik said: "Many drivers would probably say that they are more alert and more prepared for things if they drive faster, and actually there is a little bit of support for that point of view.
"But it’s by no means sufficient to compensate for the effect of the speed. They are not able to override or repeal the laws of physics."
Richard Allsop, professor of transport at University College London, supports this view. "The key basis for the power law is not sophisticated statistical modelling,” he said. “It’s simple but careful before-and-after comparisons in situations where speed has changed for some reason, usually because the limit has changed.
"The kind of evidence on which the power law is based is directly relevant to the situation we may be facing."
A DfT spokeswoman said the department had not yet made its own predictions on probable casualty changes if the speed limit did rise, but confirmed that it would be basing these on the power model.
Mike Penning, road safety minister, said: "The department is carrying out detailed work to assess the potential economic, safety and environmental impacts of increasing the national speed limit on motorways to 80mph. We will publish this work and consult fully on our proposals early next year."
Click here to read the full Guardian report.