Study on Short-Term Induced Traffic and CO2 Emissions by Adding Highway Traffic Capacity.

Increasing traffic capacity through building more roads can mitigate traffic congestion and improve vehicle travel speed. However, it is also widely believed that this kind of road development encourages vehicle use, which then leads to an increase in traffic volume and subsequent increases in CO2 emissions. There is therefore often widespread unease, or even active lobbying against, plans to build new roads. Although it cannot be denied that road developments do impact upon traffic volume, it is the contention of this study that this impact is less than is commonly thought, and that (1) increases in road traffic volume are largely due to changes in the socio-economic situation (in other words, overall traffic volume increases regardless of whether or not the existing roads are developed), that (2) increases in traffic volume on arterial roads are largely due to the diversion of traffic from minor roads to arterial roads and that (3) road improvements can actually either reduce CO2 emission volumes or at the very least hinder their growth. The relationship between road improvements, induced traffic volumes and CO2 emission volumes requires analysis based on data observation. Existing research on induced traffic has tended to target certain arterial roads only, and has not taken into consideration the diversion of traffic. This study looks at phenomena that appear a relatively short time after the road has been improved, and uses observational data to empirically determine whether and to what degree such development contributes to induced traffic volumes and CO2 emissions.