Abstract
We propose an optimal actuation of operational commands for regularizing bus headways. Assuming that a transit headway control system manages the bus operation by issuing reference arrival times at the next station for a bus, the problem is how to implement the control decisions for the bus in terms of three nonexclusive alternative actions: holding the bus at stops; varying bus speeds; and controlling traffic lights. Mathematical programming provides the basis of the approach. The constraints specify the bus trajectory model and the operator objectives are formulated as a multi-objective cost function solved by a lexicographic method. Results for a bus run on a single segment between two stops highlight the properties of the solution. A simulation study of an entire transit corridor in Quebec City, Canada, shows the advantage of the method over both headway control based on pure holding at stops and on one that combines holding and absolute transit signal priority.
Highlights
We present a method for generating optimal trajectories for transit systems operating under real-time control
The bars for riding time are approximately equal for no control (NOC), holding at stations (HOL), and holding plus TSP (H+P) since no speed guidance is applied in these scenarios
We presented an efficient solution for implementing the target arrival time at the station for headway correction of transit systems
Summary
We present a method for generating optimal trajectories for transit systems operating under real-time control. We consider that operators may wish to perform the control actions to (i) achieve the target arrival time with minimal deviation; (ii) improve user experience with less holding at stations; (iii) mitigate negative effects of TSC on traffic; (iv) avoid long waiting times during red light phases; and (v) maintain constant speed along the itinerary These objectives are sometimes conflicting, so the solution method should provide the operator with a systematic way to balance them in realizing this multi-objective task. The main contributions of the work reported in the paper are (i) integrated optimization of holding, speed guidance, and multiple traffic signals; (ii) operator choice to prioritize five performance criteria of the multi-objective approach; (iii) straight integration with any headway control method providing an implicit or explicit target arrival time; and (iv) results of case study scenario simulation of a trunk line in Quebec City, Canada. The results indicate that the combined actuation on holding, speed guidance, and TSC successfully improves many metrics important for the operator, bus users, and surrounding traffic
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