Few have dug into the potential long-term effects self-driving cars will have on cities -- the place where driverless cars will likely be most in demand.

The National League of Cities released a report last year to examine how technology could affect the future of American cities. NLC looked at America's 50 most populated cities, plus the largest cities in each state. The City of the Future: Technology & Mobility report explored how 68 cities across the United States are planning for the arrival of driverless cars.

It turns out we're not really planning for self driving cars at all. Most cities seem not to be forecasting driverless cars in their future. The report found that only 6 percent of cities consider driverless technology in their long-term transportation plans. Half of the cities are planning for new highway construction.

"A majority of cities do not have concentrated efforts to prepare for new transportation innovations," the authors found. "Though half of the cities surveyed have explicit plans for new highway and infrastructure construction and maintenance, the majority of cities are not taking into account the effect of driverless technology."

Once driverless cars get here, it's likely that our cities will be entirely unprepared for them. The following potential issues that urban planners will have to navigate as they design the cities of the future.

Where do the driverless cars park?

People in modern-day cities do more than drive their cars. They also park them.

City parking -- lots, street spaces, garages -- are designed with adequate space for people to get in and out of those cars. Driverless cars can be parked tightly together to conserve space.

At this stage, it's unclear exactly how we'll handle parking self-driving car. When not in use, could they be tucked away in garages outside of the city center? If that's the case, how do those who own the cars summon them?

Or, could driverless cars park alongside regular people-driven cars? Or perhaps self-driving cars don't need parking at all.

Will self-driving cars play nice with people and vehicles?

Self-driving cars are "smart" enough to follow the rules of the road sans street signs and traffic lights. Driverless vehicles can essentially follow instructions served up by a traffic management system. An automated car would be told whether to pass through an intersection or to stay put and wait its turn.

Most would welcome the reduction of traffic lights, poles and signs in urban areas. This de-cluttering would certainly open up the streets. This could be a design upgrade for our city.

Aside from car-to-car communication, urban planners will also need to consider how driverless cars cooperate with the millions of pedestrians and cyclists in an urban area? If you're a city dweller, you've observed first-hand the threat that oblivious pedestrians and fearless bikers pose to everyone's safety.

There are also buses and other cars to consider. Last month, a Google self-driving car collided with a public bus on a Silicon Valley street. "Clearly Google's robot cars can't reliably cope with everyday driving situations," said John M. Simpson of the nonprofit Consumer Watchdog.

How will automated cars influence traffic flow?

We don't yet know how self-driving cars will affect traffic circulation. On one hand, more people might rely on them for transportation, leading to fewer car purchases and thus fewer cars on the roads.

Another possibility? The arrival of driverless cars could drive down the cost of regular cars -- leading more people to buy them. "The weird irony of driverless cars is that more people might drive," Illinois Tech architect Marshall Brown speculated in a recent Wired piece.

So are cities ready for self-driving cars? Not really, but it's still too early to make more concrete plans with so many unknowns regarding how self-driving cars will operate in real life. Cities likely won't start baking self-driving cars into their urban planning until they get here.