Resumen
Free flowing vehicle speed data are essential in the geometric design consistency evaluation of highways. Video based data acquisition technique can be used for the purpose. Further, in four-lane median divided highways, the vehicle needs to be monitored for the presence of other vehicles in the adjacent lane. The video log helps in vehicle tracking, vehicle classification, identification and monitoring free flow conditions along a stretch. Now, the vehicle speed is estimated from the travel time to cross known trap length. The accuracy of the speed data depends on the frame rate of the camera and trap length. The maximum possible error in estimating the travel time to cross known trap length is found to be one frame and its effect on vehicle speed estimation decreases with increase in trap length. However, observation (parallax) error increases with trap length. So it needs optimization. A field study is conducted with varying trap length to come up with the optimum values. The findings show that an optimal value of trap length is 15m. Also a video based data acquisition setup has been proposed to track free flowing vehicle. Finally, data set from video recording technique have been compared with standard data set. Results show that the speed measurements based on the proposed video based method are not statistically different from the standardized equipment.