A new study says autonomous vehicles may decide to cruise around rather than parking when not in use, raising concerns that they may add to gridlock in downtown areas.

Human-driven cars must be parked when the humans get out of the vehicle. But driverless cars can just keep going and won’t have the same incentive to actually park for periods of time, the study says. Their decision may be to keep moving around rather than entering a lot or garage and paying to park; one expert said an AV is expected to cost about $0.50 per hour to operate, so it’ll be cheaper to keep driving. And that could spell traffic trouble in already crowded areas.

Read the whole story here and let us know in the comments–do you share the study’s concerns?