CO2 project – CO2 effects on drivers’ state and performance

Carbon dioxide (CO 2) is an odourless and colourless compound present in the atmosphere at a concentration of approximately 400 parts per million (or ppm). While CO 2 is not toxic per se, exposures to very high concentrations (> 10000 ppm) may have moderate to severe implications for human health, e.g., high blood pressure, dizziness, nausea or even life-threatening conditions such as hypercapnia or loss of consciousness. Short-term exposures to moderate-high levels (1000-5000 ppm) are also known to produce mild symptoms such as fatigue, discomfort or headache. Moderate-high CO 2 levels have been detected inside vehicles. Evidence suggests that a large number of drivers may frequently expose themselves to CO2 concentrations that could affect their state and, more importantly, their ability to drive safely. This potential effect, however, has received no attention in the literature. To address this knowledge gap, the present project aimed to elucidate the possible effects of moderate- high CO 2 levels on driver fitness and performance. In addition, this project analyzed the influence of other factors, such as driver mental workload and driving time, on the effects of CO 2. This second objective builds on the idea highlighted by two recent reviews that CO 2 effects may be more easily detectable when task demands are sufficiently high. Besides learning about the role of CO 2 on driving safety, this project also aimed to provide recommendations to Senseair (partner in the project) on the calibration of future in-vehicle CO 2 sensors. To address these objectives, a study was designed to be conducted on the VTI simulator in Linköping (Sweden). The simulator was placed inside a 24m 3 tent specially built for this project in order to manipulate and regulate the indoor CO 2 levels. This was done by means of a system that allowed pure CO 2 mixed with fresh air to be injected into the appropriate concentrations. The indoor CO 2 level was automatically regulated through sensors and a closed-control system. Specifically, thirty-two healthy adult participants (41 years old on average) performed two computerized cognitive tasks and drove the simulator under levels of 700 (normal indoor), 1500 and 3000 ppm in counterbalanced order.