Abstract
A comprehensive and detailed knowledge of the microscopic behaviour of vehicles under actual traffic conditions would be of undoubted value to the practicing highway and traffic engineer in many aspects of his work. To this end many traffic flow theories have been developed which attempt to describe in mathematical terms the realistic behaviour of traffic. Among the more recent developments are the car following theories which are particularly relevant when traffic concentrations are high. In this paper the authors briefly describe the car following theories and illustrate an experimental technique they have developed for testing the theories under actual traffic conditions.