Office of Safety and Operations 

Research and Development 

1

Integrated Highway Prototype Using Cooperative 

Driving Automation (CDA)

Connectivity helps automated vehicles safely merge and then harmonize across a traffic stream. The Federal Highway 

Administration’s (FHWA’s) integrated highway prototype used up to five SAE International® Level 2+ vehicles(1) on a 

closed track to perform platooning, cooperative merge, and speed harmonization maneuvers. The research team 

then analyzed the potential benefits of applying CDA to highways. Additionally, vehicles from a university partner 

helped demonstrate the viability of these maneuvers across diverse vehicle platforms, which will be key to successful 

operation of cooperative vehicle applications in the future.

© Getty Images Plus.

USE CASE ARCHITECTURE 

Figure 1 shows how vehicles communicated equipped 

with CARMA PlatformSM(2) which enables them to platoon 

and merge cooperatively. A Vehicle-to-Everything (V2X) 

Hub(3) served as the roadside interface between the 

infrastructure and the vehicles. CARMA CloudSM(4) was 

used to run the speed harmonization algorithm and 

provide speed guidance to vehicles based on traffic data 

(traffic data were simulated for this testing).1

Figure 1. Graphic. Diagram of CARMA Ecosystem.(2,3,4,5,6)

IMPROVED SAFETY

Minimal disturbances to the traffic flow 

and increased confidence in merge 

locations may lead to safer roads for 

road users.

REDUCED CONGESTION

Initial traffic studies conducted via 

simulation suggest that this approach 

may lead to an increase in throughput 

by up to 28 percent overall and up 

to 80 percent in the bottleneck area and to a 

reduction in travel times up to 35 percent. 

 

IMPROVED EFFICIENCY 

With a reduction in speed oscillation 

and stop-and-go traffic, the same 

simulation traffic studies reveal that 

fuel efficiency, energy efficiency, 

and CO2

 emissions can see 

improvements by up to 50 percent in bottleneck 

areas. 

BENEFITS TO TRANSPORTATION

TSMO = transportation systems management and operations; ADS = automated driving 

systems; RSU = roadside unit; ITS = intelligent transportation systems.

Source: FHWA.

1 The algorithms will be published in the report, which is in progress: A. Ghiasi, S. Ramyar, J. Smet, K. Garvis, E. Leslie, J. Ma., Y. Guo, T. Yang, and Y. Yuan. 

Project Report for CARMA Proof-of-Concept Integrated Highway Prototype 2 . Washington, DC: Federal Highway Administration.
2

EVALUATION OF THE CONCEPT 

Limited integration testing occurred using the test facilities at Turner-Fairbank 

Highway Research Center in McLean, VA. Full-integration testing and 

subsequent test phases were completed at a test facility in Auburndale, FL. 

The facility has a 2.25-mi oval track that is compatible with testing the freeway 

applications used by the CDA integrated highway prototype (figure 2).

INTEGRATED HIGHWAY PROTOT YPE USING COOPERATIVE DRIVING AUTOMATION

STANDARDS

This technology uses the following 

standards established by SAE 

International:

 SAE J3216_202107TM: Taxonomy and 

Definitions for Terms Related to 

Cooperative Driving Automation for 

On-Road Motor Vehicles.

(8)

 SAE J3016_202104TM: Taxonomy and 

Definitions for Terms Related to 

Driving Automation Systems for 

On-Road Motor Vehicles.(1)

 SAE J2735_202007TM: Vehicle-toEverything Communications Message 

Set Dictionary.(9)

 Original map: © 2022 Google® EarthTM, modified by FHWA to show labels and colored lines.

 Figure 2. Photo. Aerial view of the test track.(7) 

The core testing involved three vehicles carrying out a single scenario that combined the three applications. 

The steps were carried out to test the scenario shown in figure 3 through figure 10.

35 mph 35 mph

cloud

cloud

30 mph

cloud

30 mph

30 mph

Figure 3. Graphic. Mainline vehicles start their 

run on the track.

Figure 4. Graphic. Mainline vehicles communicate with CARMA 

Cloud to receive relevant guidance for platooning.(3,4)

Figure 5. Graphic. Mainline vehicles and merging vehicle 

approach the merging area.(4,6)

Figure 6. Graphic. Mainline vehicles slow down in response 

to speed harmonization and merging vehicle begins 

communication.(3,4)

Source: FHWA.

Source: FHWA.

Source: FHWA.

Source: FHWA.

1. Vehicle 1 and vehicle 2 recognize each 

other and begin platoon negotiations.

2. A platoon forms and vehicle 2 recognizes 

vehicle 1 as the platoon leader.

Vehicle 3 engages CARMAin 

preparation for merging area.

1. Vehicle 1 sends a TCR requesting platooning 

rules.

2. Cloud replies to all vehicles via V2X with a TCM 

containing speed and platooning rules.

1. Vehicle 3 sends a TCR.

2. Cloud replies to vehicle 3 via V2X with a 

TCM containing speed rules.

3. Vehicle 3 accelerates to its target speed.

TCM = traffic control message; TCR = traffic control request.

Vehicle 1 continues to send 

TCR messages and receive 

TCM messages.
https://highways.dot.gov/research/

3

RESULTS AND LESSONS LEARNED

The validation testing done conducted by the U.S. 

Department of Transportation’s Volpe National 

Transportation Systems Center showed that the 

vehicles could execute front-join (figure 11), rear-join 

(figure 12), and speed harmonization operations 

(figure 13) on a closed test track. The plotted results in 

figure 11 through figure 13 show a subset of data for 

the front-join, rear-join, and speed harmonization 

operations, respectively, demonstrating the consistency 

of speed through the operation’s execution. From the 

validation testing, the team identified potential areas of 

improvement, such as improved lane-keep abilities and 

advanced sensing capability integration, to enable 

object detection and avoidance functions. 

INTEGRATED HIGHWAY PROTOT YPE USING COOPERATIVE DRIVING AUTOMATION

cloud cloud

35 mph 35 mph 35 mph

Figure 7. Graphic. Merging vehicle negotiates with mainline 

platoon leader to identify a trajectory to merge and to 

receive the platoon rules.(4)

Figure 8. Graphic. Mainline vehicles communicate with CARMA 

Cloud and begin platooning under received guidance.(4)

Figure 9. Graphic. Merging vehicle has joined the platoon, 

and the platoon travels together through the remaining 

speed harmonization zone using MOMs to communicate.

Figure 11. Graph. Results of adjacent lane front runs.

Figure 10. Graphic. All three vehicles exit speed harmonization 

as noted by a TCM previously received from CARMA Cloud,(4) 

and all three vehicles resume following the speed limit.

Source: FHWA.

Source: FHWA.

Source: FHWA.

MOM = mobility operations message.

Source: FHWA.

Source: FHWA.

When the platoon enters the merge area, a 

vehicle in the merge lane sends a request 

to the lead vehicle asking to join the main 

line. The leader accepts the request.

Vehicle 1, vehicle 2, and vehicle 3 

communicate using MOMs.

Vehicle 3 follows its trajectory 

onto the mainline.

Note: The platooning algorithm allows 

joining a platoon in a common or 

adjacent lane. Platoon negotiations 

will not start until the merging vehicle 

is at least adjacent to the mainline.
TITLE OF TECHBRIEF

4

For more information, please contact the CDA Program at CDA@dot.gov

INTEGRATED HIGHWAY PROTOT YPE USING COOPERATIVE DRIVING AUTOMATION

FUTURE POTENTIAL IMPROVEMENTS 

Simulation – Continued simulation testing will allow for 

further refinement of potential standards for features in a 

wider range of scenarios. 

Increased number of vehicles – Increasing the 

number of vehicles and testing partners can allow for 

further refinement of the technology and testing of more 

complicated scenarios outside of simulations.

Cut-in merge – The current testing focused on joining 

the platoon from the front and the rear. Further testing 

may study the opening of a gap for a joining vehicle 

to enter the platoon somewhere in the middle.

Cellular communication – The transportation safety 

band, which is the standard frequency band used to 

communicate between vehicles and infrastructure, is in 

high demand. Investigations can be conducted as to 

whether messages for this technology can potentially be 

delivered through other means, such as cellular, to 

prioritize and better manage the transportation safety 

band usage.

Public road testing – Testing the concept on public 

roads will identify how the technology behaves in a 

real-world environment. Improvements to the concept 

need to be made. Vehicle controls need to be improved 

so vehicles can reliably remain in their own lane at 

highway speeds. Sensing capabilities should also be 

integrated into the platform to enable object detection 

and avoidance functions. 

TO LEARN MORE AND FOLLOW UPDATES:

CDA Program 

https://www.fhwa-stol.org/

V2X GitHub

https://github.com/usdotfhwa-OPS/V2X-Hub

CARMA Platform

https://github.com/usdot-fhwastol/carma-platform

Figure 13. Graph. Results of speed harmonization (high).

Source: FHWA.

 

 

Figure 12. Graph. Results of adjacent lane rear runs.

Source: FHWA.

 

1. SAE International. 2018. Taxonomy and Definitions for Terms Related to Driving Automation 

Systems for On-Road Motor Vehicles. SAE J3016_202104. Warrendale, PA: SAE International. 

https://www.sae.org/standards/content/j3016_202104/, last accessed May 30, 2023.

2. FHWA. n.d. “carma-platform” (software and configuration files in GitHub repository). 

https://github.com/usdot-fhwa-stol/carma-platform, last accessed April 12, 2023.

3. FHWA. 2023. “V2X-Hub” (software and configuration files in GitHub repository). https://

github.com/usdot-fhwa-OPS/V2X-Hub, last accessed April 13, 2023.

4. FHWA. 2023. CARMA Cloud (software). Version 4.3.0.

5. FHWA. 2023. CARMA Messenger (software). Version 4.4.0. 

6. USDOT. n.d. “CARMA” (webpage). https://its.dot.gov/cda, last accessed May 30, 2023.

7. Google®. 2016. Google® EarthTM (software).

8. SAE International. 2020. Taxonomy and Definitions for Terms Related to Cooperative 

Driving Automation for On-Road Motor Vehicles. SAE J3216_202107. Warrendale, PA: SAE 

International. https://www.sae.org/standards/content/j3216_202107/, last accessed July 

16, 2021.

9. SAE International. 2020. V2X Communications Message Set Dictionary. SAE 

J2735_202007. Warrendale, PA: SAE International. https://www.sae.org/standards/content/j2735_202007, last accessed June 21, 2022. 

FHWA-HRT-24-024

HRSO-40/12-23(200)E

Recommended citation: Federal Highway Administration. Integrated Highway Prototype 

Using Cooperative Driving Automation (CDA) (Washington, DC: 2023) 

https://doi.org/10.21949/1521464