Eco-Approach and Departure System for Left-Turn Vehicles at a Fixed-Time Signalized Intersection

Abstract

Abstract:This research proposed an eco-approach and departure system for left-turn vehicles at a fixed-time signalized intersection. This system gives higher priority to enhancing traffic safety than improving mobility and fuel efficiency, and optimizes the entire traffic consisted of connected and automated vehicles (CAVs) and conventional human-driven vehicles by providing ecological speed trajectories for left-turn CAVs. All the ecological speed trajectories are offline optimized before the implementation of system. The speed trajectory optimization is constructed in Pontryagin's Minimum Principle structure. The before and after evaluation of the proposed system shows the percentage of vehicles that drive pass the intersection at safe speed increases by 2.14% to 45.65%, fuel consumption benefits range 0.53% to 18.44%, emission benefits range from 0.57% to 15.69%, no significant throughput benefits is observed. The proposed system significantly enhances the traffic safety and improves the fuel efficiency and emission reduction of left-turn vehicles with no adverse effect on mobility, and has a good robustness against the randomness of traffic. The investigation also indicates that the computation time of proposed system is greatly reduced compared to previous eco-driving system with online speed optimization. The computation time is up to 0.01 s. The proposed system is ready for real-time application.

An Extensive Investigation of an Eco-Approach Controller under a Partially Connected and Automated Vehicle Environment

“…The results indicate that most eco-driving approaches that have attempted to minimize the fuel consumption and emissions of individual vehicles have shown decreasing trends in environmental benefits with an increase in the congestion level, and eco-driving approaches focused on improving global fuel efficiency and emission reduction could generate larger environmental benefits with an increase in the congestion level [16,17]. Under a partially connected and automated vehicles environment, the impact of the MPR of CAVs on the environmental benefits of eco-driving is relatively straightforward.…”

“…With emerging connected and automated vehicle (CAV) technology, a brand new fuel efficiency improvement technology known as "eco-driving" has become an emerging research focus [6]. Most existing eco-driving research can be categorized into eco-driving on the freeway [7][8][9][10][11] and eco-driving on signalized arterials [12][13][14][15][16][17][18][19]. Eco-driving on the freeway mainly focuses on smoothing the vehicles' speed profile to reduce traffic oscillations which can cause extra energy consumption and emissions.…”

“…These strategies are not feasible for real-world implementation in the near future due to their poor robustness against the impedance from conventional vehicles and the randomness of traffic [16]. To overcome this drawback, queue theory and car following theory were introduced into some eco-driving studies on signalized arterials to predict the location and motion of conventional vehicles [16][17][18][19][20][21]. It is expected that these eco-driving controllers will be functional in a partially connected and automated vehicle environment and can be implemented as long as CAV technology is introduced in the near future [17].…”

“…To overcome this drawback, queue theory and car following theory were introduced into some eco-driving studies on signalized arterials to predict the location and motion of conventional vehicles [16][17][18][19][20][21]. It is expected that these eco-driving controllers will be functional in a partially connected and automated vehicle environment and can be implemented as long as CAV technology is introduced in the near future [17]. However, it is still difficult to affirm the limitations, risks, or benefits of these eco-driving controllers in mixed traffic flow [22].…”

“…The evaluation results indicated that these controllers could generate considerable fuel consumption benefits under low saturation conditions but cause significant harm to mobility and even have some negative effects on the vehicle fuel efficiency under high saturation conditions [16]. To eliminate this limitation, some pure "win" eco-driving controllers were developed to reduce the total fuel consumption of traffic systems while doing no harm to the throughput of intersections, if not benefitting them, which could indirectly control conventional vehicles by utilizing car-following models [16,17]. The existing brief evaluations on these controllers only confirm the benefits, few limitations, and feasible conditions that they may provide for further improvement and implementation [23].…”