Mcity unveils digital twin, making its physical AV testing facility available for free in the virtual world

Images of Mcity test track and digital twin

The first open-source digital twin of the Mcity Test Facility—the University of Michigan’s test center for connected and autonomous vehicles and technologies—is now available to the public, giving researchers around the world a new free tool.

A digital twin is a virtual representation of a physical environment that also exchanges data with that environment, enabling simulation and testing. The new Mcity digital twin, developed with support from the National Science Foundation, is the first open-source digital twin for mobility systems testing, including autonomous driving. It provides a faster, safer, less expensive way to test autonomous and connected vehicle software.

Researchers anywhere can use the facility’s features—with a variety of road materials, markings, signals and intersections—to test their autonomous algorithms without having to make the trip to Ann Arbor.

“This takes our almost 10-year-old track and puts the digital replica directly over it,” said Greg Stevens, Mcity’s director of research. “That’s a living, breathing manifestation of that physical track where people can do mixed reality testing and development.”

The digital twin works with TeraSim, an open-source traffic simulator developed by Mcity researchers. It introduces other road users, such as pedestrians, cyclists and other drivers, and generates safety-critical events like potential collisions. Using traffic behavioral models calibrated with real-world data, it simulates both normal and high-risk driving scenarios. 

Mobility officials have touted AVs, along with connected vehicles and infrastructure, as a path to safer, more efficient and equitable transportation. Still, a great deal of research remains ahead before the technologies will produce everyday benefits for a large portion of the population. Testing in the real world takes time and money and creates a host of safety issues, but virtual testing can enable control software to demonstrate a high level of safety ahead of that stage.

“You can drive millions of miles in your AV in a digital twin built off of a real-world environment before your AV actually touches the real world,” said Darian Hogue, an Mcity software engineer who helped develop the digital twin. “With this, we can control all kinds of factors. That includes controlling and manipulating simulated pedestrian traffic—a factor that is random in the real world. This focuses and accelerates simulated testing.”

Opened in 2015, the Mcity Test Facility is the world’s first purpose-built proving ground for connected and automated vehicles. Its physical features include: 

• A simulated downtown area with urban streets.
• A 1,000-foot straightaway, plus access ramps, a curve and a traffic circle.
• Multiple road surfaces with a variety of road markings and crossing types.
• Traffic signals and traffic signs.
• Bridge deck, underpass, guardrails, barriers and crash attenuators.
• House and garage exterior with accessibility ramp for first-mile/last-mile testing, deliveries and ride hailing.

Mcity is continuously adding new features, and officials have worked to make the facility and its technologies available to a larger group of researchers. In 2022, a $5.1 million grant from the National Science Foundation funded development of Mcity’s digital infrastructure, enabling remote use of the Mcity Test Facility—dubbed Mcity 2.0. The 2022 grant also funded creation of the Mcity digital twin.

Mcity officially launched its remote use capabilities in October. Researchers operating from their home bases can test their autonomous algorithms in virtual and mixed reality environments by connecting to Mcity’s cloud-based digital infrastructure. Using 5G wireless communications, they can control physical vehicles and traffic signals on Mcity’s test streets and receive real-time data in return—all while protecting proprietary information.

“What differentiates the Mcity digital twin is that it supports virtual testing, while remote use involves testing a physical vehicle at our physical test track from a remote location,” said Mcity Director Henry Liu, professor of civil and environmental engineering and the Bruce D. Greenshields Collegiate Professor. 

“As an open-source tool, the Mcity digital twin lowers barriers to use of the test facility by technology developers and researchers. The digital twin could also help developers better prepare for on-site testing at Mcity.” 

Written by Jim Lynch, U-M College of Engineering