Many interstates I have seen have large clear spaces beside & between the paved areas ie the central median and the shoulders.
They also are often associated with service roads and ramps - and these often have much less traffic.
If you are looking at an interstate to land that means to me there is no adjacent flat clear areas nearby ie it is locked in by hills or urban development. (otherwise I'd be using the flat clear areas -ie fields- beside the interstate, before I ever would choose to land in busy traffic). Even flying over a causeway, I'd ditch beside it unless it was devoid of vehicles.
One of my biggest concerns is flying over cities which are absolutely packed with buildings and busy roads and no greenspace. As I progress over these, I am eyeballing golf courses, right of way space beside high tension lines, railways, large empty parking areas.
Edit;
Oh, it would be idiotic to expect traffic to part for you. They are never going to see you or react appropriately. Cars are basically unpredictable, 3000lb, rolling blocks of dumb.