The effects of small roundabouts on emissions and fuel consumption: A case study

The effects of small roundabouts on emissions and fuel consumption were evaluated using the ‘car-following’ method in a before/after study. The results showed that at a roundabout replacing signalised junction, CO emissions decreased by 29%, NOx emissions by 21% and fuel consumption by 28%. At roundabouts, replacing yield regulated junctions, CO emissions increased on average by 4%, NOx emissions by 6% and fuel consumption by 3%. The results indicate that the large reductions in emissions and fuel consumption at one rebuilt signalised junction can ‘compensate for’ the increase produced by several yield-regulated junctions rebuilt as roundabouts.