User-based transit signal priority in a connected vehicle environment accounting for schedule delays and environmental impacts

Considering recent advances in connected vehicle technology, we propose and assess two user-based transit signal priority (TSP) strategies. The first proposed strategy is designed to minimize the total user delay of a signalized intersection, while, in the second, we account also for minimising bus schedule delay. Besides the traffic flow indicators, we measure the environmental impact of the proposed TSP strategies. We compare the performance of the proposed strategies with a conventional TSP ring barrier controller in a microscopic simulation environment, for a case study considering two adjacent signalized intersections located in Helsinki, Finland. Moreover, in order to perform a fair comparison between different proposed TSP strategies, we propose and evaluate a total social cost function. The evaluation of social cost is a practical way for multi-criteria assessment of traffic control strategies, where environmental impacts and traffic flow indicators are converted into comparable units. The findings of this paper show that implementing the proposed strategies is effective in improving TSP performance as well as reducing environmental impacts.