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How an Automated Car Platoon Works

Posted by the U.S. DOT's Volpe National Transportation Systems Center

Instead of cars driving as individual units on highways, automated driving systems (ADS) allow cars to connect and exchange information, enabling coordinated movements. That can mean more capacity on roads, and faster, more efficient travel.

In one study, a car platooning proof-of-concept with five Cadillacs with automated longitudinal control was tested and evaluated at Aberdeen Proving Ground, a U.S. Army test facility in Maryland.

The study was conducted by experts from the Federal Highway Administration’s (FHWA) Turner-Fairbank Highway Research Center (TFHRC), U.S. DOT’s Volpe National Transportation Systems Center, and the Aberdeen Test Center.

“We are focusing on the cooperative side of automated driving systems,“ said Taylor Lochrane, PhD, Cooperative Automation Research Program technical manager at TFHRC. “If vehicles can communicate with each other and the infrastructure, we can use that capability and coordinate traffic more efficiently and save our economy billions in wasted time and fuel.”

How Automated Driving Systems Enable Car Platooning

For a vehicle to platoon, an onboard computer is  connected to a vehicle-to-vehicle communications device that receives and transmits data using Dedicated Short-Range Communications.

“By adding connectivity between cars, we can manage traffic with clusters of vehicles instead of individual vehicles,” said Wassim Najm, PhD, chief of Advanced Vehicle Technology at the Volpe Center. “With better traffic management, we can improve mobility.”

At the Aberdeen site, the test cars successfully shared information, such as whether they needed to speed up or slow down to follow the lead vehicle at a desired distance. Najm’s team piloted the technical and analytical work for testing and evaluating the car platooning proof-of-concept.

“We built the test procedures for the track to test the vehicles using vehicle-to-vehicle communications,” said Najm. “We now have a better understanding of the performance parameters and the test procedures needed for advancing car platooning technology.”

Lochrane’s team programmed the onboard computers with platooning algorithms developed by FHWA and partners from earlier projects. Vehicle computers control braking and acceleration, and also take in radar data—part of adaptive cruise control—to create Cooperative Adaptive Cruise Control.

“The followers follow the vehicle in front and listen to all the other vehicles in the stream and that’s how they all communicate—the computers are able to compute the current and predicted trajectory of the vehicle to maintain their position,” said Lochrane.

What’s Next?

The FHWA-Volpe Center team found some weaknesses and anomalies with the proof-of-concept technology that will inform the design of future car platooning prototypes. TFHRC and the Volpe Center experts are now working on making data and research available to anyone interested in ADS technology.

“We are developing an open source automated vehicle platform using a robot operating system architecture for leaders in industry and academic researchers to collaborate on advancing cooperative automated driving technology,” Lochrane said.

The team hopes to eventually partner with industry to have car platooning prototypes that can also automate steering to enable lane changing and merging onto a highway.

Read the full report: Test and Evaluation of Vehicle Platooning Proof-of-Concept Based on Cooperative Adaptive Cruise Control

cars following in a straight line

The testing and evaluation of car platooning technology was a collaboration between the Federal Highway Administration’s Turner-Fairbank Highway Research Center, U.S. DOT’s Volpe National Transportation Systems Center, and the U.S. Army. (FHWA photo)