Before long, self-driving cars will deliver a lot of benefits. First and foremost, they'll increase safety. Accidents won't be eliminated, but surely will produce better results than humans, who play an outsized role in the 30,000 fatalities in US roads. They'll also increase productivity—work in the car!—and perhaps even let you sneak in a nap.

Not everyone is looking forward to the age of autonomy, though. One potential loser? Local governments.

Once the car's in charge, it's a safe bet we won't do things like speed, run reds, park illegally, or drive drunk. And that means we won't be fined for doing those things. That's going to put the squeeze on city budgets, according to a Brookings Institution report.

"Local governments have viewed their sources of revenue and planned around revenue from the perspective of, 'We can tax people in a very structured and predictable manner,'" says Kevin Desouza, a professor at Arizona State University and one of the report's authors. They can count on catching us breaking the law often enough to keep the money flowing. But once that's passed, "they're going to lose out in the long run."

There are no national numbers indicating how much American drivers shell out in traffic violation fines, but the report puts the total in the hundreds of millions of dollars. Los Angeles, for example, collected $161 million from parking tickets in 2014. Twenty cities in California take in $40 million every year from towing cars, splitting that money with the tow companies.

On top of that, if the theory that self-driving cars will lead people to own fewer cars holds up, revenue from registration fees will drop as well.

It's mostly going to come down to utility-driven revenue for local governments, rather than asset-driven revenue. Kevin Desouza, School of Public Affairs at Arizona State University

Again, great news for people who don't like, or can't afford, paying fines and fees. But that money finances things like transportation infrastructure and maintenance, public schools, judicial salaries, domestic violence advocacy, conservation, and many other public services, the report notes.

Meanwhile, we'll still expect our cities to pay to keep the roads in good shape, since no matter who's driving, potholes stink.

There is good news here for government bean counters. Car crashes are an expensive business, and we all pick up the tab. According to a NHTSA report, "public revenues paid for roughly 7 percent of all motor vehicle crash costs [in 2010], costing tax payers $18 billion in 2010, the equivalent of over $156 in added taxes for every household in the United States." Radically fewer accidents means radically more dollars that can be spent on nicer things.

Throw in other upsides like increased productivity (we can work in the car), reduced congestion (cars that talk to each other will improve traffic clow by eliminating the speed fluctuations that create the “accordion effect"), and reduced fuel consumption (smarter systems drive more efficiently and find parking faster), and we can save some $211 billion a year if half our vehicles are autonomous, according to a 2013 report by the Eno Center for Transportation.

Still, those savings won't directly replace the revenue municipalities raise from parking tickets and the like. What they need to do, Desouza says, is redirect resources and generate revenue in smarter ways.

A good place to start would be a per-mile driving charge, to supplement (or replace) dwindling money provided by gas taxes and vehicle registration fees. That will be tricky if the pervasive anti-taxation climate in state and federal government hangs on, but the shift is important to make, Desouza says. "It's mostly going to come down to utility-driven revenue for local governments, rather than asset-driven revenue."

And this would be a great time to put traffic cops to work stopping crimes.