SUVs are classified as "trucks" for the purpose of C.A.F.E. regulations, and those regulations are more lenient on gasoline efficiency for trucks. As a result, the auto industry happily built SUVs safe in the knowledge that high SUV sales wouldn't lower their overall fleet mileage and therefore not risk violating the CAFE regulations.
On the other hand, most other highway regulations do not consider SUVs to be trucks. As a result, SUVs sit in this sweet spot where they get to pretend they're a truck when it's advantageous to be a truck (avoiding CAFE regulations) and pretend that they're a car when it's advantageous to be a car (highway regulations).
My modest proposal was to get rid of this loophole. If you're going to let SUVs be classified as trucks for the purpose of determining whether they are subject to CAFE regulations, then classify them as trucks for the purpose of highway regulations. If you're driving an SUV on a highway that has different speed limits for cars as opposed to trucks, then you have to adhere to the truck speed limit. Because you're a truck. If you're driving an SUV on a highway which bans trucks from the leftmost lane, then you are banned from the leftmost lane. Because you're a truck.
People who are driving a truck because they actually need it for truck-like activities (hauling lumber, pulling a boat, delivering baked goods, whatever) won't be seriously inconvenienced, since they're not going to be doing any of those car-like things anyway.
If you really want to take this principle to its conclusion, you would even have to stop at the weigh stations to ensure that you're not over weight, and to check your log book (you keep a log book, right?) to ensure that you're not violating the laws regarding the maximum permitted number of hours behind the wheel of a truck. Because you're a truck.
Of course, the loophole could be closed the other way, too: Alter CAFE to classify SUVs as cars. Either way works for me. Just make the CAFE regulations and highway regulations agree on who is a car and who is a truck.
As I noted, it looks like economic forces have solved the problem on their own, but in case SUVs suffer a new surge in popularity, you've got my proposal in your back pocket, ready to spring into action.
Yes, this modest proposal is out of order, but it seemed more timely than the planned topic (solving the problem of identity theft), which I will still get to next time, if there is a next time.