Tennessee Department of Transportation and Vanderbilt University’s Institute for Software Integrated Systems


Nashville, TN




2023 ACEC Engineering Excellence Awards National Recognition
2023 Southern District of ITE Best Special Project
2022 ACEC Tennessee Grand Conceptor Award
2023 ITS America Best of ITS Award
2023 ITS Tennessee Project of Significance Award

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I-24 MOTION is a first-of-its-kind testbed implemented by the Tennessee Department of Transportation and designed by Gresham Smith in conjunction with Vanderbilt University. Known as I-24 Mobility Technology Interstate Observation Network (or I-24 MOTION), this groundbreaking active testbed runs along the busy and often congested I-24 corridor, and it was designed to allow TDOT and researchers to study how all types of vehicles interact with one another and the state’s infrastructure in order to advance congestion mobility across Tennessee. In essence, it provides an “MRI for traffic” by providing an environment for testing advanced traffic management and automated vehicle technologies in real freeway traffic.

Funded by the Federal Highway Administration Congestion Mitigation and Air Quality Improvement Program, the project transformed a four-mile section of I-24 in the Nashville-Davidson County metropolitan area into an experimental testbed, using over 276 ultra-high-resolution cameras that convert images into a digital model of how every vehicle behaves with unparalleled detail. Over time, the I-24 MOTION project will allow automakers, researchers and TDOT to create, deploy and validate new technologies for connected/automated vehicles and traffic management.

ultra-high-resolution cameras
mile-long corridor
of its kind testbed
camera shots of cars driving on a highway

An “MRI for Traffic”

To bring the testbed to life, Gresham Smith designed an “MRI for traffic,” consisting of a network of 276 ultra-high resolution cameras mounted on 40 poles spaced every 500 to 600 feet to capture data on a four-mile section of I-24 that frequently experiences congestion and a broad range of traffic conditions. The sensing strategy deploys cameras with overlapping views across the corridor. By translating data from each camera, the team can develop a complete, yet anonymous, trajectory for each vehicle with measurements made many times per second, quantifying how vehicles are accelerating and decelerating as they move through the corridor.

a graphic of a TDOT smart corridor

Getting Smart on Managing Traffic

The I-24 MOTION project was intentionally located within the larger I-24 SMART Corridor, which equips 30 miles of I-24 and Murfreesboro Road with active traffic management technologies including variable speed limits, dynamic message signs, ramp meters and arterial signal timing improvements. The MOTION testbed has already led to new findings about traffic congestion; less than a month after activation, TDOT was able to begin optimizing how the SMART Corridor operates. Using the information gathered on this testbed, I-24 MOTION provides insights for industry to build better products and allows TDOT to better understand how to make the most out of these products for managing infrastructure assets. This collaboration with the industry allows for faster development of new traffic jam breaking technologies that benefit all drivers as well as other infrastructure owners.

camera shots of cars driving on a highway

The First Experiment

The first testbed use was the U.S. Department of Energy’s sponsored research with the CIRCLES Consortium, which studied the possibility of smoothing out traffic by introducing 100 Nissan Rogue vehicles equipped with advanced driver-assist systems, including both stock and a new dynamic adaptive cruise control. The project aimed to reduce instabilities in traffic flow, such as “phantom” traffic jams that cause congestion and waste fuel. In the fall of 2022, the CIRCLES project team collected over 3,700 hours of driving in one day alone. The data is currently under evaluation and shows promise that just a small percentage of similarly equipped vehicles on the road can reduce traffic jams, resulting in up to 40% less fuel consumed.

people looking at a screen with cars driving on the highway

What’s Next

TDOT has already begun to identify ways that the testbed could enhance existing operations, such as optimizing SMART corridor approaches and improving safety of first responders. Future experiments are envisioned with external collaborators working in concert with TDOT, such as automotive original equipment manufacturers and suppliers, other researchers, traffic simulation software developers, freight and logistics operators, other infrastructure owners, ITS product manufacturers and enterprise networking and data solutions providers. More information is available on the I-24 MOTION website.

Gresham Smith’s professionalism, engineering expertise and previous Intelligent Transportation System design experience proved to be essential to the project’s success, along with their flexibility, cooperation and close coordination with other stakeholders. The result is a ‘traffic MRI’ instrument that will revolutionize how traffic is measured and will provide new insights into how traffic flow influences individual vehicle behaviors. This will provide safer and more reliable conditions along I-24. Lee J. Smith Director, Traffic Operations Division at TDOT