Calibration-Free Arterial Link Speed Estimation Model Using Loop Data

Abstract

This paper presents a calibration-free model to estimate the average speed of moving vehicles in a link, from the upstream intersection until 40–60 m from the downstream intersection's stop line. The proposed model calculates link speed from travel time, which in turn has two components: cruise time and signal delay. The cruise time is based on the speed measured by loop detectors. The signal delay is first calculated using the Webster formula. A coefficient is derived to portion the signal delay to the link segment upstream from the stop line. This model, which takes input from loop detectors and signal timing parameters, has been tested against simulated data. The results show that the model is able to provide link speed estimate to within 5 km/h error at least 95% of the time. This accuracy is better than that of the British and Iowa models and is only slightly lower than the Illinois model. However, being calibration-free, the proposed model here has a distinguished advantage in practical implementation.