Estimating Residual Phase Duration for SPaT Messages
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SPaT (Signal Phase and Timing) refers to the current phase at a signalized intersection together with the residual time of the current phase for each approach. Accurate SPaT messages can be used to construct a speed profile for a vehicle to reduce its fuel consumption as it approaches or departs from an intersection. This paper proposes SPaT estimation algorithms at an intersection with a semi-actuated signal, using accurate, real-time, signal phase measurements. The algorithms are evaluated using high-resolution data from an intersection in Montgomery County, MD. The proposed algorithms can be readily implemented at signal controllers. The study supports three findings. First, real-time information dramatically improves the accuracy of the prediction of the residual time. Second, as time increases the prediction of the residual time may increase or decrease. Third, since drivers differently weight errors in predicting 'end of green' and 'end of red', drivers on two different approaches would prefer different estimates of the residual time of the same phase.
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