US Patent 11904890 Lane change system for lanes with different speed limits

Embodiments disclose a method and a system to operate an autonomous driving vehicle (ADV). In one embodiment, a system determines a source lane speed limit (SLSL) for a source lane (SL) and a target lane speed limit (TLSL) for a target lane (TL), where the SLSL is greater than the TLSL. The system generates a first trajectory for the ADV to follow the SL, the first trajectory having a modified speed corresponding to the TLSL instead of the SLSL. The system generates a second trajectory for the ADV to change from the SL to the TL, the second trajectory having a speed corresponding to the TLSL. The system determines a first cost and a second cost for the first trajectory and the second trajectory respectively based on a cost function for comparison. The system controls the ADV according to a trajectory with a lowest cost.