Tesla's new Navigate on Autopilot feature performs much worse than a typical human driver at things like changing lanes and passing and poses a serious safety risk, according to Consumer Reports.

"The system's role should be to help the driver, but the way this technology is deployed it's the other way around," said Jake Fisher, Consumer Reports' senior director of auto testing in an emailed statement. "It's incredibly nearsighted. It doesn't appear to react to brake lights or turn signals, it can't anticipate what other drivers will do, and as a result, you constantly have to be one step ahead of it."

While Tesla's ordinary Autopilot system helps to keep a car in its lane and maintain a safe following distance behind other cars, Navigate on Autopilot promises to do much more. With Navigate on Autopilot, a car can automatically change lanes and turn onto on-ramps and off-ramps as it follows a route from the car's navigation system . It can also change lanes to pass slower-moving cars. This level of automation is available as a setting that the driver can select.

When Consumer Reports tested Navigate on Autopilot, the car frequently changed lanes too close to other cars and sometimes passed cars in ways that violated traffic laws, the consumer group said.

"The Navigate on Autopilot driver-assist feature overpromises and under-delivers, with lives on the line," David Friedman, vice president of advocacy at Consumer Reports, said in a statement.

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