An instrument is described, capable of automatically measuring and recording vehicle speed, distance, acceleration and vehicle length. It consists of photoelectric cells, mounted in a movable rubber pad on the pavement, connected to a 7-channel analog tape recorder placed in a perked car. A third photoelectric cell is required to compensate for variations in light intensity and illumination. The tapes are later converted for computer processing and evaluation. A separate track on the tape is reserved for verbal comment regarding the traffic situation. A signal simulator is also provided. The errors introduced by the use of a magnetic tape are smaller than those caused by the photoelectric cells. Results from accuracy tests show that the figures for the acceleration of the vehicle were least satisfactory. Equally there was a rather large error in the measurement of vehicle lenght. The influence of the lighting conditions is also commented. Best results were obtained under an overcast sky.
Abstract