The Impact of Inter-Vehicular Distance on CO₂ Emissions in On-Road Driving Hybrid Vehicles

A major challenge for internal combustion engine vehicles is reduction of CO₂ emissions. Hybrid vehicle demand has recently increased as a countermeasure. However, in hybrid vehicles, the frequency of motor and engine usage varies depending on the driver's driving style, even when driving the same vehicle on the same route. As a result, CO₂ emissions can differ significantly between drivers. Analyzing the impact of driving characteristics on CO₂ emissions can contribute to improving the efficiency of engine and motor control in vehicles, leading to further reductions in CO₂ emissions. Therefore, this paper examines the impact of different driver behaviors on CO₂ emissions in hybrid vehicles. In this study, two drivers were asked to follow a preceding vehicle on real roads, and various data were collected during these drives. Conducting the experiments on actual roads allowed us to obtain results that closely reflect real-world driving conditions, thereby enhancing the relevance of the findings. The use of hybrid vehicles, which are rapidly gaining popularity, in these experiments is considered particularly valuable. Among the two drivers, significant differences in inter-vehicular distance (the distance between the preceding vehicle and the driver’s vehicle) were observed. Consequently, this study focused on how such differences affect CO₂ emissions and successfully demonstrated that inter-vehicular distance, a quantitative indicator of driving behavior, influences CO₂ emissions in hybrid vehicles. The results showed that drivers who maintained a larger intervehicular distance tended to produce lower CO₂ emissions. This outcome was influenced by differences in driving resistance and the amount of engine usage. Drivers who maintained a larger inter-vehicular distance tended to experience lower driving resistance. Additionally, regarding engine usage time, drivers who kept a larger inter-vehicular distance spent more time driving using only the electric motor. As a result, the engine's operating time was reduced, leading to lower CO₂ emissions.