Cortina Safety Products EZ Grab Delineator 45" Post, 3" Hip Collars with 10 lb Base, 03-747RBC-2, Orange, 2 Pack

Q: Can I attach a street sign to the post and how... is there a kit that is sold separately? Also, will this blow over in a nice breeze?

The base is heavy and the post should withstand a good breeze. The post is a hollow molded plastic piece (like a heavy duty plastic baseball bat). I don't know if that helps you with the attaching a sign part of the question.

Q: Can I purchase additiinal bases to add weight?

The base slides down over the tube so I see no reason why you couldn't add a second base. I didn't see the base on Amazon but you can buy them here https://www.zoro.com/cortina-trim-line-base-black-10-lb-15-in-w-03-752-10/i/G4060935/

Q: I'm considering buying these for a driving school. How durable are they? Can they be knocked down without breaking?

They are durable and pliable we have ours out all year long even in the extreme cold and they do fine. They are also tall so they would be visible, the base is 15 x 17 so if they are hit the base might get stuck under the car.