This is especially true for people alone behind the wheel. One study on people's ability to predict when they would fall asleep was done in 1993 for the American Automobile Association. It had them perform monotonous tasks on a computer. All they had to do was to predict whether they would fall asleep in the next two minutes. Barely half of them were able to accurately predict their first onset of sleep.
Most people like to have someone in the car they can talk to.
Cars become obstacles and the fellow citizens who are driving them cease to be seen as human beings. Another study, conducted for the AAA Foundation in 1996, looked at road rage. The study identified more than 10,000 incidents in the 1990s. Several of the experts we interviewed said studies to quantify the negative effects of driving alone are in short supply. However, they said, common sense and personal experience show that driving alone increases road rage and alienation while driving with others has the opposite effect.