On expressways, it is widely noticed that drivers do not consider the safety spacing between vehicles according tothe running speed. Therefore, the objectives of this research are to get, at first, the size of the problem, and to classify the psychological demands which result in this dangerous situation. Also, a questionnaire survey, on hearing base, was conducted on drivers, and it was found that “the desire to speed” is the main reason for running in short spacing. Next, another experimental work was designed to find the spacing necessary to transmit this desire to the preceding driver. This can give an explanation to the effecting factors in the problem of short spacings on expressways.