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Public Roads - Winter 2020

Winter 2020
Issue No:
Vol. 83 No. 4
Publication Number:
Table of Contents

CarmaSM: Driving Innovation

by Taylor Lochrane, Laura Dailey, and Corrina Tucker

FHWA's cooperative driving automation program is transforming transportation.

FHWA recently expanded its CDA fleet by four new passenger vehicles. Three different makes and models are shown here. All use the third phase of CARMA (CARMA3).
FHWA and its partners recently released the third iteration of the CARMA software platform. CARMA promotes collaboration and participation from communities of engineers and researchers to advance the understanding of cooperative automated driving.

Cooperative driving automation (CDA) has the potential to improve transportation safety and efficiency, facilitate freight movement, increase productivity, and save money by reducing the need to widen roadway lanes. The Federal Highway Administration developed the unique CARMA PlatformSM and CARMA CloudSM (collectively, CARMASM) to support the research and development of CDA features in support of transportation systems management and operations (TSMO).

"Automated vehicles, consistent with their name, operate autonomously or on their own," says Chris Stanley, the program manager for FHWA's Saxton Transportations Operation Laboratory and the senior director of surface transportation research at Leidos. "FHWA is enabling these vehicles to work together for the public good, improving transportation safety and mobility."

CARMA is a cooperative effort among FHWA, the Federal Motor Carrier Safety Administration, the Maritime Administration, the Intelligent Transportation Systems Joint Program Office, and the Volpe National Transportation Systems Center. Together, the agencies work to facilitate collaboration, research, and testing in CDA as well as the future of the Nation's transportation system.

What Is CARMA?

The overarching purpose of CARMA is to transform transportation, improving efficiency and safety through automated vehicles working together with roadway infrastructure.

To fully understand what CARMA is and how it can improve transportation efficiency and safety, it is important to understand how the current iteration of CARMA developed. CARMA1 started out as a proof of concept. A software package developed to enable vehicles to communicate their longitudinal movements with each other, CARMA1 marked the start of FHWA's cooperative automated vehicle fleet.

Next, the team developed CARMA2, a platform built on open-source software. The goal of this phase was to engage with the industry on CDA in order to expand existing automation capabilities and to reduce research and development time. CARMA2 runs on a computer inside a vehicle. The computer interacts with the vehicle's devices and microcontrollers, including onboard units and after-market sensors such as radars. The platform manages the controller area network (CAN bus) messages for the vehicle to speed up or slow down, gathers data from connected sensors to understand the vehicle's environment, transmits the onboard unit messages to other vehicles, and processes incoming messages from other vehicles and infrastructure in order to cooperate with other vehicles. The platform also provides many plug-ins that support cooperative driving tactics, such as cruising, yielding, lane changing and merging, platooning, and speed harmonizing.

The research team then developed CARMA3, the latest version of CARMA released in July 2019 and now simply called CARMASM, to collaborate with the research and development community. It consists of CARMA Cloud and the CARMA Platform.

CARMA is an open-source software that enables researchers and engineers to develop and test their CDA features on properly equipped vehicles. It is available on the GitHub development platform at for any researcher to download and use. By making CARMA publicly available, FHWA and its partners hope to set the foundation for interoperability across vehicle makes and models and encourage the safe introduction of the technology onto the Nation's roads.

CARMA Cloud is a downloadable, cloud-based, open-source service that enables communication between cloud services, vehicles, road users, and infrastructure devices. CARMA Cloud enables the roadway to provide information to support safe operation for new TSMO strategies. This technology facilitates cooperation among vehicles and roadway infrastructure through communication.

The CARMA Platform provides cooperative research functionality to an automated driving system. By using CARMA Cloud to provide information about what's ahead (such as traffic incidents, road weather conditions, and work zones), the CARMA Platform enables automated vehicles to interact and cooperate with infrastructure and other vehicles, improving the performance of the existing transportation system.

Features of the CARMA Platform

The developers designed the CARMA Platform with flexibility in mind. It is built on Robot Operating System (ROS) to encourage modular design so that components can be easily swapped out to experiment with different combinations. It includes vehicle-to-everything (V2X) communications capabilities to compose, transmit, receive, and parse V2X messaging and can work with any radio device.

The platform also includes three application planning interfaces (APIs). The planning plug-in API enables users to install plug-ins for either strategic planning or tactical planning of vehicle behaviors and trajectories to exercise particular algorithms and cooperative interaction. The controller plug-in API provides for the implementation of low-level motion-planning algorithms. Finally, the hardware driver API enables users to install the platform on any properly equipped vehicle, as long as drivers are installed that connect to the various vehicle sensors and controller equipment.

Additionally, the third phase of CARMA software also features:

  • Localization, motion planning, and obstacle detection and avoidance.
  • Autoware™ components that are adaptable to work with other platforms.
  • Environment sensing with light detection and ranging (LiDAR), radar, video, and MobilEye® -integrated roadway-sensing devices.
  • Society of Automotive Engineers (SAE) level 2 steering and speed control while staying in lane.
  • Basic safety message broadcasting using data from the CARMA system.

FHWA and its partners are developing further CARMA features, and more information will be available online as these features are identified and created.

Developing Strategies for Key Scenarios

The CARMA Program aims to develop a concept of operations for TSMO strategies, including basic travel, traffic incident management (TIM), work zone, and weather scenarios.

"The results of this research will accelerate stakeholder collaboration expediting identification of readiness needs that will stimulate deployment of cooperative driving automation technology while advancing safety, security, data, and application of artificial intelligence," says John Harding, the leader of FHWA's Connected/Automated Vehicles and Emerging Technologies Team.

Basic travel. The first basic travel scenario CARMA will explore is merging onto a highway. The second research priority is navigating a signalized intersection.

Traffic incident management. The CARMA team will research three TIM-related scenarios. The first is when vehicles must move out of the way of first responder vehicles driving toward an incident. The second priority for investigation is the move-over law, in which approaching vehicles should move out of the lane adjacent to stationary emergency vehicles with flashing lights. The third scenario being explored during this phase is changing lanes on a freeway in response to an incident blocking a travel lane ahead.

Work zone management. The first scenario CARMA will explore is a one-lane, two-way traffic taper. The second-priority scenario for investigation is a road closure with diversion.

Road weather management. CARMA will investigate the scenario of a vehicle adjusting speed and preparing for other adjustments at the beginning of a weather event zone.

CARMA Collaborative

FHWA established the CARMA Collaborative to bring together diverse stakeholders supporting the future of the transportation industry. The effort bridges gaps among several stakeholder groups and forms a community of existing and prospective CARMA users invested in developing intelligent transportation solutions and cooperative automated driving systems to improve transportation efficiency and safety. The CARMA Collaborative provides opportunities to cultivate relationships, share expertise, pilot transportation technologies, implement cooperative automated driving systems, and strengthen the transportation industry for public benefit.

The CARMA Collaborative advances the understanding of CDA and the impacts it can have on mobility, cultivates technology that enables cooperative automated driving systems, and accelerates use of CARMA by stakeholders to support the collaborative development and adoption of cooperative and automated technologies. The collaborative facilitates active engagement, interaction, and discussion on the use of CARMA through its open-source platform, stakeholder engagement, and webinars to share information.

Get Involved!

The latest version of CARMA is now live on GitHub and open for collaboration. The unique CARMA Platform enables users to download and add this software to a properly equipped vehicle with automated driving technology. Download the software to begin collaborating with FHWA and its partners in improving the roadways today.

Partner Spotlight: FMCSA

The Federal Motor Carrier Safety Administration (FMCSA) is the leading Federal government agency that is responsible for regulating safety of commercial motor vehicles. FMCSA's priority is to reduce crashes, injuries, and fatalities that involve large trucks and buses. FMCSA has joined the CARMA Collaborative in order to push the limits of CARMA by improving transportation safety. The four tractors provided by FMCSA are the next generation for test vehicles that will support Society of Automotive Engineers (SAE) Level 2 and Level 3 commercial motor vehicle automation research. The areas of research for the tractors include roadside inspections, advanced driver-assistance systems, performance, platooning, driver readiness, and cybersecurity.

CARMA will explore two basic travel scenarios, including merging onto a highway. Here, the text bubbles indicate in-vehicle warning messages for cars that are merging as well as cars in the travel lane.
This phase of the CARMA project investigates three scenarios related to traffic incident management, including changing lanes on a freeway in response to an incident ahead with a responding emergency vehicle.
The CARMA team will examine two work zone management scenarios, including one-lane, two-way traffic taper in which a single lane is used for alternating traffic in each direction, as shown here.
CARMA will explore a road weather management scenario in which vehicles must change speed and prepare for other adjustments at the beginning of a weather event zone.

Taylor Lochrane is the technical program manager for CARMA, leading the open source development and collaboration efforts of CARMA with partners and stakeholders. He earned B.S, M.S., and Ph.D. degrees in civil engineering focused in transportation from the University of Central Florida.

Laura Dailey is the communications manager of the Saxton Transportation Operations Laboratory, overseeing marketing and engagement activities. She earned an M.S. degree from Drexel University and B.S. degree with a marketing concentration from Elon.

Corrina Tucker is a junior communications specialist in the Saxton Transportation Operations Laboratory leading outreach activities. She holds a B.A. degree in digital media from Penn State and specializes in technical writing and multimedia.

For more information, contact Taylor Lochrane at or visit