CO2-project CO2 effects on drivers´ state and driving performance

Important results from the project

Moderate-high CO2 concentrations can easily be reached inside conventional vehicles, specially while using the recirculation mode (e.g., to maximize the air conditioning effects). Until recently, these levels were thought to be benign for health, but accumulating evidence has shown that they can affect the human psychophysiological state and performance. Within CO2-project, it was investigated whether drivers exposed to moderate-high levels of CO2 see their state and performance affected, which would would represent a risk factor for driving safety.

Expected long term effects

Contrary to our expectations, we found that the CO2 effects on driver fitness and performance were greater at levels of 1500 ppm than at 3000 ppm. In fact, the effects at 3000 ppm were similar to those at baseline (700 ppm). The found effects included greater subjective and objective drowsiness, increased cardiac activity and poorer vehicle control. Performance of a simultaneous auditory task, and longer driving time did not exacerbate the effects of CO2. It should be noted that the observed effects were small and did not lead to significant problems in driving performance.

Approach and implementation

A study was designed at VTI where 32 healthy adult participants (half of them women) performed various cognitive tasks and drove in a simulator located inside a plastic tent where CO2 concentrations were manipulated. Participants were exposed to levels of 700, 1500 and 3000 ppm through two experimental sessions on two separate days. The participants´ heart and ocular activity was continuously recorded through electrodes to determine their physiological state. The driving scenario consisted of a rural road with mild curves and light traffic and lasted 40 minutes.