Tesla .. no driver

Driving down the 90 in PA. yesterday and I passed a Tesla and there was no driver. Now I know they've been out there, but to drive up on one was a bit weird. There was a guy in the passenger seat and one in the back. I watched that car from the rear view mirrors and that car traveled in the center of the lane perfectly. It never wandered a bit, it was weird how on online it was. I confess I was looking behind more than forward, lucky I didn't drive off the road.