Abstract
The effective setting of offsets between intersections on arterial roads can greatly reduce the travel time of vehicles through intersections. However, coordinated control systems of urban arterial roads often do not achieve the desired effect. On the contrary, they are very likely to increase the traffic congestion on arterial roads, resulting in more delays of the platoon with more exhaust emissions, if the coordinated control system does not have effective settings. Meanwhile, taking into account increasing environmental pollution, measures are needed to solve the conflict between environmental and traffic management. Thus, in order to ensure the smooth flow of urban arterial roads while considering the environment, this paper develops a bi-objective offset optimization model, with reducing delays of the platoon on arterial roads as the primary objective, and reducing exhaust emissions as the secondary objective. The proposed bi-objective model is based on the division of platoon operating modes on arterial roads, and more pollutant types, including NOx, HC, and CO, are considered when measuring environmental impact. Further, the modified hierarchical method, combining the branch and bound approach with the introductions of a relaxation coefficient, is employed to solve the model. By introducing a relaxation coefficient, the modified hierarchical method overcomes the defects of the traditional one. Finally, Xi Dajie Road in Beijing was taken as an example. The results showed that the bi-objective offset optimization model, considering both the delays and emissions of the platoon reduced delays by up to 20% and emissions by 7% compared with the existing timing plan. If compared with the offset optimization model considering delays only, such a model increases delays no more than 3% and reduces emissions by 6%.
Highlights
In urban transportation systems, reasonable adoption of coordinated control of arterial roads could ensure smooth flow and alleviate urban traffic congestion
Optimal offsets were obtained for the offset optimization, considering both delays and emissions of the platoon using the modified hierarchical method
In order to prove the applicability of the model established in this paper, the proposed offset optimization model was compared with the existing timing plan and the offset optimization considering delays only
Summary
Reasonable adoption of coordinated control of arterial roads could ensure smooth flow and alleviate urban traffic congestion. The signal offset is an important parameter of the coordinated control on urban arteries, which decides the effect of the coordinated control for adjacent intersections and represents the time relationship, determined by the difference between a defined point in the coordinated green and a system reference point [1]. The signal offset has a considerable impact on the performance of the coordinated control system. The offset optimization of arterial roads can greatly reduce the travel time of vehicles, enhance stability, and smooth operation of urban traffic while improving arterial traffic congestion. There is an urgent demand to quantify the impact of arterial offset optimization to improve coordinated control systems
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