stop moving car

i m working on unity game engine.
i need to stop moving car for 6seconds then again the car start moving, i m using this script but it is not working please help? i have used box collider in the path of car to stop the car through box coliider then the car destroy box collider and wait for 6 seconds and again start moving on its path.
here is the script.

@ CosgunHalil