Limit website to one item group level at a time?

Is there a way to limit the products show in the website to just one level at a time. For instance if I have two parent Groups; Car and Trucks and in the car group I have 2 door car group and 4 door car group and in the truck group I have 2 wheel drive trucks and 4 wheel drive trucks. Inside those 4 end groups I have sorted all my vehicles. I only want the products view to show two items, Cars and Trucks. When a user clicks the Cars link they get a page that show the 2 door and 4 door car groups.
-2 wheel drive
-4 wheel drive

At it works out of the box the Products webpage show all the item groups and all the child groups, showing 6 items. This defeats the purpose of organizing the products into groups.

Did anyone has the solution for this? I also still have this problem.