Joint maximum-likelihood estimation of speed and acceleration from existing roadway vehicle detectors

Transportation agencies have invested in extensive infrastructure for vehicle detection and speed estimation. It is of interest to measure vehicle accelerations at an intersection to evaluate the impact of traffic signal control on energy, emissions and safety. This paper explains how to use inductive loops and magnetometers in speed trap configurations to measure acceleration in addition to speed and develops an algorithm for doing so. The algorithm was tested using approximately 7,000 vehicles and a GPS probe vehicle was used to provide ground truth. It was found that the root mean squared error (RMSE) between GPS and algorithm estimates is approximately 0.04g.