For safe travel you should identify a planned path where your vehicle wil be ahead along your path for at least how many seconds?

You follow the vehicle ahead of you by 3 seconds, you should never plan a path where you will be unless you are switching lanes and need to know how much space you have because while driving things can change in an instant, for good defensive driving just be prepared for anything at any time, and always follow vehicles by 3 seconds from the time their rear bumper passes an object until your front bumper passes the same stationary object