A Left-Turn Planner for Platoon: Enabling a Smoother Unprotected Left-Turn at an Intersection

Platoon technologies can enhance traffic efficiency and lower fuel consumption to facilitate the development of modern transportation systems. However, existing platoon technologies struggle to achieve commercial implementation, primarily due to the incomplete operation design domain (ODD). They cannot handle all scenarios, especially unprotected left-turn scenarios at an intersection. In such a scenario with narrow driving space, platoons face frequent interactions with surrounding vehicles. It poses three challenges: i) slower left-turn completion; ii) jiggering left-turn maneuvers; and iii) higher collision risks. To address these challenges, an optimal-control-based left-turn planner for platoon is proposed in this paper. It has the following features: i) proactively fight for more driving space to enable faster left-turn completion; ii) integrate both behavior level and planning level for smoother left-turn maneuvers; iii) take a person-by-person driving countermeasure for reducing collision risks; and iv) be with string stability of platoon. A comprehensive evaluation is conducted. Results demonstrate the proposed planner can take person-by-person countermeasures when facing the competing vehicle with different driving behaviors. It outperforms the baseline planner by 20.6% in completion efficiency, and 5.8% in collision risk. Moreover, the average computation time of the proposed planner is 145 milliseconds. Results indicate that the proposed planner is ready for real-time commercial applications.