Climate Changeswings Roundabouts

Wednesday, 24 March 2010

Road traffic - apparently a primary cause of climate change - is grinding to a halt due to gloomier, wetter weather, according to the latest issue (163 TR1) of the ICE Transport journal. A 10 year study by UK transport engineers has found slower roundabouts are to blame.

Lead author, Goktug Tenekeci of Pell Frischmann says, 'Roundabouts are a widespread form of junction globally and are particularly common in the UK. The results identified that wet and dark conditions had a substantial effect on the entry capacity of normal-size roundabouts.'

There have been many international studies on roundabout capacity, but none until now has quantified the reduction in damp and gloomy conditions.  A 1986 study suggested a 5% reduction at night, whereas the latest research - based on 14,500 rush-hour measurements at four roundabouts in Leeds - found an average reduction of 25% when running wet and under street lights.


The authors conclude that the overall rush-hour capacity of the study roundabouts is actually 7% less as a result, and that heavier rainfall resulting from climate change will lead to further reductions and even greater congestion. 'Designers should consider the outcomes of this paper, particularly when new designs are produced or assessment is carried out for roundabouts operating at or near capacity,' says Tenekeci.


Abstracts of all papers can be read at the ICE's virtual library at For more information please contact the editor Simon Fullalove on +44 20 7665 2448 or email