If it's not already obvious, in a lot of places, when regulations are promoted to reduce waste and benefit public/environmental health, a large number of people will get angry and vote for those who'll want to maximize damage just because. If regulations promoting smaller cars were ever suggested in these places, some smiling politician would announce a mandate that vehicles be 5 tons or greater with anything smaller being banned, and compilations of people who worried about the environment would be circulated and heavily mocked online.

This is misunderstanding why people respond that way.

There are a lot of people who can't easily change their behavior, e.g. because your theory is that they should buy smaller cars but their business requires a vehicle that can carry heavy loads once a week and they can't afford to buy a separate vehicle for that so the larger vehicle has to be their daily driver. Then a tax meant to induce a change in behavior is received by them as an unavoidable tax hike, which they naturally resent and oppose, and because of the nature of politics they'll then propose the opposite of whatever you're trying to do to them.

What you really need to do is to make it more possible for them to do the thing you want. For example, right now if you want to have a modern compact car for most use and an old truck you use once a week for truck stuff, you have to register and insure two vehicles. That isn't currently economical, but it's what you want to happen so they're not just driving the truck at all times.

What you want to do is to make it economical. Only charge a registration fee for someone's primary vehicle and waive the cost for a second one, and make insurance work in such a way that having two vehicles doesn't have any higher liability premiums than driving the same total number of miles in one vehicle.

Then they can do what you want, and in fact have the incentive to, because the smaller car will save them gas most of the time but they still have the truck when they need it.