Effects of in-car CO2 concentration on driving: a preliminary study with taxi drivers.

Objectives: To evaluate the effects of carbon dioxide (CO2) concentrations in automobiles on driving performance. Methods: A driving simulator experiment was conducted with eight taxi drivers. The experiment was conducted under low CO2 concentration (<500 ppm) and high CO2 concentration (5,000 ppm) conditions. To evaluate driving performance and cognitive function, three measures were employed: a two-back task, an LED response task, and a driving assessment. The driving assessment used scoring criteria from the driving license proficiency test. Results: Poisson regression analysis showed that wobble (p=0.044), signal failure (p=0.045), contact (p=0.003), and wheel departure (p=0.005) were significantly increased under high CO2 concentration conditions. Generalized linear mixed model (GLMM) analysis showed that reaction time in the LED response task was significantly reduced under high CO2 concentration conditions (p<0.001). On the other hand, the GLMM analysis of the two-back task showed no significant effect of CO2 concentration (incorrect response rate: p=0.733, non-response rate: p=0.485). Conclusions: These results suggest that elevated CO2 concentrations may have a negative impact on driving behavior, especially skill-based driving behavior. On the other hand, the effects on cognitive tasks requiring working memory were limited. The results of this study suggest that managing CO2 concentration in vehicles is important for maintaining safe driving and raise the need for specific measures, such as the development of systems for measuring, predicting, and controlling CO2 concentration in vehicles, and the implementation of driver education programs.