That's the problem with becoming dependant on a behavior that you want to prevent.
I keep arguing for a flat tax to fund a Citizen's Dividend; while the Universal Basic Income guys largely want carbon taxes or wealth taxes, so as to not tax the poor. I tell them, what do you do when there is no longer an enormous gap between rich and poor? Tax the rich even more? What do you do when we switch to nuclear solar power? Let the poor starve? My system fails if and only if the entire economy fails: it skims a bit off the top of all income, and it doesn't matter who is receiving that income or for what.
What do you do about all the lost ticket revenue when you stop having traffic violations? How do police react when they lose the ability to use a traffic stop as an excuse to find drugs in cars?
You stop doing those things and start being honest. I just went to a hearing to argue for the elimination of fines for wrong-way parking on one-lane, two-way, residential side streets. These are those roads with parking on both sides, where you pull off the road if another car approaches from the opposite direction. You do not cross oncoming traffic to park on the left; you are always driving in the lane which carries oncoming traffic. I outlined all of the safety issues caused by right-side parking, all of the legal-but-unsafe maneuvers encouraged by right-side-only parking, and all of the reasons why the safety issue of parking on the left side of the street does not apply to one-lane street; but, most of all, I pointed out that many families in these areas cannot afford a $32 fine (literally: I've had people indebted to me for $20 because they could not survive without it, scraping for months to get it back to me), and that this just gives imperative to learn to shoplift, deal drugs, or engage in prostitution.
Fines terrify poor people. Fines create poverty. Fines encourage crime. You instill fines in poor neighborhoods where you want to control severely-detrimental behaviors; imprisonment works on the upper classes, since fines are cheap. I still advocate beatings for petty crime, because I don't believe someone shoplifting a few cans of Campbell's Soup warrants 30-90 days in jail--which is practically a death sentence, since they come out thousands of dollars behind, fired from their job, evicted from their home, and with no hope of getting back on their feet. Cane them a few times and send them home. If they're desperately hungry, they're going to steal food no matter what you do, so lowering or raising the punishment bar isn't going to change anything; most college frat jackasses, however, will quickly realize they dislike ass whoopings more than they dislike not having DVDs, so there's no reason to go straight to destroying their lives over a $15 copy of Avengers and two cans of Pringles.
How do you fund roads with a gas tax when cars become more fuel efficient and eventually switch to electricity (often generated at home with solar panels)?
The electricity needed to power your car is nearly your home's entire electricity usage. You'd spend more on the charging array than you would on the car itself. I estimated $3.16 to charge a full 300 miles (my car runs 300 miles on a tank and gets filled 2-3 times per month), but some old man with a Tesla told me he pays about $4-$4.15 per full charge. (I use about 300-500kWh of electricity, and usually pay more in customer fees and transmission fees than I do for actual usage: $15/mo each for Electricity and Gas customer fee, plus as much for transmission as the cost of the actual electricity.)
It makes much more sense to take transit tax as income tax, really.