Development of a corrected average speed model for calculating carbon dioxide emissions per link unit on urban roads

The purpose of this study is to develop a “corrected average emission model,” i.e., an improved average speed model that accurately calculates CO₂ emissions on the road. When emissions from the central roads of a city are calculated, the existing average speed model only reflects the driving behavior of a vehicle that accelerates and decelerates due to signals and traffic. Therefore, the authors verified the accuracy of the average speed model, analyzed the causes of errors based on the instantaneous model utilizing second-by-second data from driving in a city center, and then developed a corrected model that can improve the accuracy. They collected GPS data from probe vehicles, and calculated and analyzed the average emissions and instantaneous emissions per link unit. The results showed that the average speed model underestimated CO₂ emissions with an increase in acceleration and idle time for a speed range of 20 km/h and below, which is the speed range for traffic congestion. Based on these results, the authors analyzed the relationship between average emissions and instantaneous emissions according to the average speed per link unit, and they developed a model that performed better with an improved accuracy of calculated CO₂ emissions for 20 km/h and below.