The publication also found that Super Cruise was better at notifying drivers when it was about to disengage. GM’s tech not only provides a clear visual alert, but uses pre-mapped road info to notify commuters in advance that they’ll have to resume control. Tesla’s approach delivers either a loud alert or a subtle icon change when Autopilot disengages, and it’s frequently an abrupt cutoff.

It wasn’t a clear-cut victory. GM’s system tended to discourage taking over, and Tesla had clear advantages in ease of use. Both fared better than many of their rivals, though. The next-closest system was Ford’s Co-Pilot 360 (52), while even luxury brands like Audi (48), Mercedes (46) and BMW (44) fared relatively poorly. Even Volvo, a safety advocate, scored a mediocre 41.

We’ve asked Tesla for comment, but it’s not likely to be thrilled with the results given its fractious history with Consumer Reports.

Whatever car you prefer, the study suggests that semi-autonomy and other driver assistant features are a long way from being truly reliable. They may save you from the mental drain of focusing on a long highway commute, but you’ll still have to be ready to steer with very little warning.