The bloom is off the rose for self-driving tech among urban transportation officials, who are planning for a future with fewer private cars.

On the one hand, autonomous vehicles offer an excellent opportunity to rethink how American cities operate, down to each lane line, crosswalk, and curb. Two years ago, the National Association of City Transportation Officials, representing 81 North American cities, published its first planning guide to self-driving vehicles, highlighting the possibilities. If everyone moves around on electric-powered transit and robotaxis, no one needs to own a car. No one needs to park a car.

So that first version outlined an elegant—albeit fanciful—vision of the cities of the future. Parks where there once were paint lines and parking meters. Residential streets with plenty of green space, with road access limited to the occasional delivery driver. More room for public transit than personal cars.

In 2019, the dream is still alive. But then there’s that other hand: If cities screw up the transition to AVs, they’ll end up with streets clogged with traffic, smogged with emissions, and little room for people to walk, bike, and scoot.

So NACTO is publishing this week a second version of the AV planning guide, one that takes a more skeptical approach to the project. After years of tensions with Silicon Valley-powered transportation companies like Uber, Lyft, and Bird, which have created traffic, pulled some riders off struggling public transit, and challenged existing infrastructure and regulations, cities are wary of those promoting new transportation services. The new blueprint is a detailed 131-page guide to what some of the most influential cities in the country believe is the best way to prep for AVs—even if no one is quite sure when the tech will arrive.

“There are good partners out there, but I don’t think it’s a bad thing for cities to be cautious,” says Kate Fillin-Yeh, who helped write the guide and is NACTO’s director of strategy. A task force of officials from 14 cities, including Boston, Minneapolis, Pittsburgh, San Francisco, and Vancouver, also helped create the updated blueprint.

To that end, this plan is much more specific about the sorts of policy calls cities should make to actually get that parks-instead-of-parking-lots future. It talks road pricing, the controversial policy that charges drivers to enter certain parts of a city in certain times of day. (In London, a cordon-based charging scheme that forces drivers to shell out big bucks for entering the city center has reduced local emissions.) Without a plan to charge AVs for the roads they use, the guide suggests, more people might use them—bad for traffic, bad for the environment, bad for the city.

The guide spills plenty of ink on the finer points of snoozy-sounding data-sharing policies—a topic which has, interestingly enough, ignited plenty of fights across US cities in the past year. The blueprint points out that autonomous vehicles might collect plenty of information about individuals’ travel, just as ride-hail and scooter companies do. It says the status quo—where private companies control the data derived from their services—doesn’t give cities the information they need to “ensure safety on public streets and manage and regulate transportation services to best serve public goals,” like sustainability and equity.

The blueprint also takes the time to teach city transportation officials about the finer points of preemption, when state or federal law supersedes local control. Uber and Lyft, for example, benefited from the Texas legislature’s power of preemption when state lawmakers in 2017 enacted a law laying out a regulatory ride-hail framework—in effect striking down a local Austin vote that had booted the ride-hail giants out of the city. NACTO advises transportation officials to maintain control of the self-driving tests, demos, and deployments in their midst. That runs counter to the impulses of many self-driving vehicle developers, who argue that a “patchwork” of local rules is preventing the countrywide rollout of technology that could save lives.

Autonomous vehicles will not arrive as soon as builders once said they would. Even the theoretical leader in the self-driving race, the Alphabet company Waymo, still keeps safety drivers behind the wheels of its nascent tech, monitoring the complex machines even as paying passengers ride in the back seats in suburban Arizona. Still, Fillin-Yeh says beginning to prep for the tech now is “essential.”

The blueprint still sketches plenty of visions for the future, the sorts of pictures that the right policy decisions might paint. It is packed with images of pedestrians and cyclists instead of honking, emissions-spewing cars. Children dart around playgrounds that replaced two-lane streets. Autonomous trains and buses, moving 15 times the number of people each hour than personal cars, have their own lanes, and occupy the most space. Some of the largest and most influential cities in the country are clearly concerned that the autonomous vehicle experiment might go poorly for them. But they are still optimistic.

“We’re again reminding everybody that the point of all of [developing technology] is cities and places that are good for people, that are sustainable, that are equitable, that thrive,” says Fillin-Yeh. “And that’s not going to happen if we double down on the mistakes we made with the invention of the car.”