Tesla’s Autopilot is probably the best known semi-autonomous driving system, but Consumer Reports says it’s not the best system on the market.

In the publication’s first rankings of semi-autonomous driving technology, Cadillac’s Super Cruise took top honors as the system was deemed to fairly capable and one of the most aggressive in ensuring the driver is paying attention.

Consumer Reports focused on a number of different factors including how capable the systems are. As part of this effort, the organization looked at “how well the cars stayed centered in their lane, how often they touched lane lines and how many times they crossed those lines.” Testers also looked at how well the cars were able to control their speed and how they dealt with stop-and-go traffic.

Autopilot and Super Cruise were deemed to be the best as the systems could “reliably keep the vehicle centered in the lane for several miles at a time.” Nissan’s ProPilot Assist and Volvo’s Pilot Assist didn’t do nearly as well as these systems had problems on curving and hilly roads. Consumer Reports also says models equipped with these systems had frequent lane departures.

Autopilot was deemed the easiest to use, while Super Cruise was the best at identifying when the system can be used safely. This is likely a result of the fact that Super Cruise can only be used on highways that have been mapped by General Motors.

A lot of attention was given to how well the systems keep drivers engaged as research has shown that people can become overreliant on the technology and not pay enough attention to their surroundings. We’ve already seen a handful of accidents where this has occurred, so it’s important that semi-autonomous driving systems ensure drivers remain alert.

This is where Cadillac’s Super Cruise has an edge as the system uses a camera to monitor the driver’s eye movements. If the system detects the driver isn’t paying attention, it can alert them by flashing red lights, sounding audible alerts and vibrating the seat.

The whole review is worth a read but, if you’re just interested in the ranking, here they are. Super Cruise was deemed the best overall, while Autopilot came in second. Nissan and ProPilot Assist system was third and Volvo’s Pilot Assist was dead last. Speaking of the latter, Pilot Assist was hammered for having poor capacity and performance, poor ease of use and relatively poor safety in regards to monitoring the driver.

According to Consumer Reports’ vice president of advocacy, David Friedman, “Consumers stand to gain a lot from the convenience of these systems, but only if automakers put safety first.”