**1. Introduction**

Automated vehicles have drawn a huge amount of attention from academia and industry in recent years because of the foreseen potential to improve driving safety and efficiency [1–3]. With researchers' continuous efforts, autonomous driving technologies have made great progress over the past few decades [4–7]. However, as one of the core modules in an autonomous vehicle system, trajectory planning remains to be challenging, especially in complicated environments. Narrow corridors are typically among the most complicated scenes, in which generating a safe, feasible, and smooth trajectory is difficult due to the exterior and interior restrictions.
