Traffic ‘evaporation’ as a result of road closure

Imagine if we closed some roads to cars and traffic congestion actually reduced as a result. This sounds counter-intuitive, yet it is exactly the effect that was revealed by research in the 1990s in a number of cities around the world. This result was described as ‘traffic evaporation’ in the seminal 1998 UK study of 100 locations.

The report showed that after a ‘settling in period’, where road capacity was reduced for private cars there was a 25% average overall reduction in traffic. Case-by-case outcomes varied substantially, but in many cases, when you reduce road capacity, existing motor traffic doesn’t just find another route. Some of it ‘disappears’, or ‘evaporates’.