Ok here is the problem, with full GDP Environment is almost impossible to control and most of the controls are related to car rules. And you need multiple and some what redundant rules.
For instance banning cars in city centers, ban low MPG cars, car emission limits are all needed (are significant levers on environment) even when you have 100% electric car transition.
Her is an fix. The policies “ban low mpg cars”, “car emission limits” , “electric car initiative” and “hybrid car initiative” should not directly affect environment.
Rename “Electric Car Transition” to “Clean Transport” and have that be the only transport input to environment. Going to 100% clean transport should not 100% eliminate transport related pollution but maybe 80% of it. A bottom limit.
I think similar to the transport sector energy and residential pollution should be handled in one node. You can have three nodes control your pollution/environment costs. “Clean Transport”, “Clean Energy” and “Clean Industry”, maybe “Clean Residential”
All transport should have environmental impact if not electrified, including buses and trains. Give them a smaller impact then cars but also allow clean transport transition to reduce their impact.
Anything that reduces CO2 should also reduce pollution? Except for CO2 storage everything that is supposed to reduce combustion should have a positive environmental impact.