The obvious way to do that is via the fuel tax, where the more you pay the more you use.
The reality is probably that it's not that well coupled to any cause, and really it's just a way to farm money from the majority of the country, who need to use motor transport to live their lives. The advertised political reason will change depending on the concerns of the populace at the time.
The reality is probably that it's not that well coupled to any cause, and really it's just a way to farm money from the majority of the country, who need to use motor transport to live their lives. The advertised political reason will change depending on the concerns of the populace at the time.