One problem related to assist has been reported for the 2021 Toyota Prius. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2021 Toyota Prius based on all problems reported for the 2021 Prius.
The lane keeping assist used in radar cruise control mode during some drive cycles will attempt to maintain the vehicle position to the far extreme of the lane and in some cases actively veer out of the lane. My safety ant others can be put at risk when the vehicle behaves outside of its design parameters like this. To solve the issue the vehicle must be pulled over, turned off, then restarted. After the restart it will resume functioning normally, maintaining lane positioning as intended within the limits of the system. The trigger for this is unknown but could be speculated that it is drive cycle dependent and may start during initialization. The problem has not been reproduced by a dealer or service center due to its intermittent nature. There are no warning indicators or lamps on when this occurs.