Concurrent physiological activity of driver and passenger when driving with and without automatic transmission in heavy city traffic

Twelve subjects were selected for a comparison of driver and passenger reactions in vehicles with automatic transmission and with manual transmission. Each subject underwent four test runs, as a driver and as a passenger with each transmission. During the tests, skin conductance (SCL and SCR), EMG from the frontalis muscle and ECG were recorded from both the driver and the passenger. Urine samples were taken in order to measure catecholamine excretion. The test driving-circuit was about 14 km in length and each test run consisted of four complete circuits. In drivers, significant differences were only found between driving with automatic and manual transmission, while other factors such as sequence of testing or the time of the day at which the test took place had no significant effects. When driving with manual transmission, rate of adrenaline excretion, skin conductance activity (SCRrpar;, heart rate and heart rate variability were significantly higher than when driving with automatic transmission or when riding as a passenger. Between the latter two conditions there were no significant differences with respect to these variables. Compared to both driving situations, the passenger situation resulted in significantly lower muscle tension. A comparison between first and second run showed significantly lower values for passengers on the second run with respect to SCR, muscle tension and heart rate.