“Mcity,” which officially opened Monday, is a 32-acre faux metropolis designed specifically to test automated and connected vehicle tech. It’s got several miles of two-, three-, and four-lane roads, complete with intersections, traffic signals, and signs. Benches and streetlights line the sidewalks separating building facades from the streets. It’s like an elaborate Hollywood set.

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This is about more than safety, too. Mcity allows engineers to test a wide range of conditions that aren’t easily created in the wild. They can test vehicles on different surfaces (like brick, dirt, and grass) and see how their systems handle roundabouts and underpasses. They can erect construction barriers, spray graffiti on road signs, and work with faded lane lines, to see how autonomous tech reacts to real-world conditions.

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Such a site is a great tool, but the technology must also prove itself on public roads. A simulated environment has a fundamental limitation: You can only test situations you think up. Experience—and dash cams—have taught us our roads can be crazy in ways we never think to expect. Sinkholes can appear in the road, tsunamis can rage across the land, roadside buildings can collapse and send debris flying. Humans can be even harder to anticipate. But even every day actions, the things we do almost subconsciously.

Ref: Inside the Fake Town Built Just for Self-Driving Cars – Wired