These are the $40 DrivewaySpike U-Turn Deterrents. They look like harmful tire spikes but are actually made of rubber so you can drive over them without puncturing your tires, but they should discourage strangers from doing the same. Me? I just lined my whole driveway with them along with a strip of ACTUAL spikes mixed in just to test myself. Will I remember where to swerve into the yard? Only time will tell!
UPDATE: Not at all. Could use a ride to work for a couple weeks while I save for new tires and airbag.
Keep going for a video demonstration.
Thanks again to Kinger, who agrees most drivers won't even notice them and proceed to drive right through your foyer.