Office of Safety and Operations 

Research and Development 

1

Cooperative Automation Driving System (C-ADS) with Road Weather 

Management (RWM) with a Lane Closure(1)

BENEFITS TO TRANSPORTATION

Vehicles and their passengers are at increased risk when operating in adverse 

weather due to low visibility and roadway surface changes such as flooding. 

These situations pose similar limitations for both human drivers and automated 

vehicles, though the extent of the limitations varies based on the sensor suite 

in use. Road operators can publish weather information that affects travel using 

TCMs to C‐ADS‐equipped vehicles(1) that request local route information with 

traffic control request messages. This system can help mitigate the effects of 

hazardous weather conditions for road users by providing early alerts and 

alternate travel paths and better equipping agencies’ response and recovery 

efforts. This information may be passed through short‐range communications 

or cellular networks. Figure 2 shows a vehicle communicating with a roadside 

unit (RSU) to avoid a road area with black ice.

EVALUATION OF THE CONCEPT

For road users to benefit from this technology in a real road‐weather scenario, intelligent transportation infrastructure 

systems must be deployed at the site to enable the Traffic Management Center to broadcast messages required by 

C‐ADS vehicles.(1)

Future next steps involve seeking collaboration with industry partners to determine best practices pertaining to the 

communication of alternative travel paths and lane closures for weather‐related incidents, and to study the behavior of 

C‐ADS vehicles(1) in these situations.

The Road Weather Management Program seeks 

to develop and promote effective tools to 

observe and predict the impacts of weather on 

the roads and to alleviate those impacts. The 

program pursues the following objectives:

 Develop a national, open observing system 

that promotes data sharing to support 

weather observation and forecasting and 

transportation operations.

 Develop resources and training methods to 

assist State and local partners in the 

deployment of weather management tools.

 Advance the state of the practice by 

developing proactive solutions and 

disseminating information on adverse weather.

 Foster a collaborative, comprehensive, and 

dedicated surface transportation weather 

research program.

© Getty Images Plus.

Figure 1. Photos. CARMASM (2) vehicle in icy road conditions.

Source: Federal HIghway Administration (FHWA).

This use case implementation focused on enabling lane closures 

around road locations affected by hazardous weather such as flooding 

or ice buildup. The Traffic Management Center systems, using CARMA 

CloudSM (3) would broadcast a traffic control message (TCM) to CARMA 

PlatformSM (4) to inform CARMA Platform of the flooded area and the 

need to change lanes or use an alternate route to avoid that location. 

The C‐ADS vehicle(1) would use this information to plan a new path of 

travel, avoiding the lane closure and thus the hazardous area. 

Figure 2. Graphic. Road weather management 

simulation scenario.

Source: FHWA.

V2X Hub = Vehicle‐to‐Everything Hub.(5)

cloud

HUB

(Roadside Unit)

Black 

Ice Area

15-mph Zone
FHWA‐HRT‐24‐022

HRSO‐40/11‐23(200)E

Recommended citation: Federal Highway Administration. Cooperative Automation Driving System (C‐ADS) 

with Road Weather Management (RWM) with a Lane Closure (Washington, DC: 2023) 

https://doi.org/10.21949/1521462

TITLE OF TECHBRIEF

2

USE CASE ARCHITECTURE

CARMA Cloud(3) allows users to create traffic controls on 

road sections affected by hazardous weather using a 

satellite‐based map. V2X Hub(5) receives traffic control 

requests from the C‐ADS‐equipped vehicle,(1) obtains 

relevant TCMs from CARMA Cloud, and can broadcast 

these TCMs to the C‐ADS‐equipped vehicle. The 

C‐ADS‐equipped vehicle can apply traffic controls from 

received TCMs to its high‐definition map and adjust its 

path by changing lanes out of the closed lane. The 

C‐ADS‐equipped vehicle also reduces its speed to the 

advisory speed limit. After exiting the road region affected 

by hazardous weather, the C‐ADS‐equipped vehicle can 

change lanes back into its original lane and increase its 

speed back to the normal speed limit.

RESULTS AND LESSONS LEARNED

The use case was successfully demonstrated and tested at 

Summit Point Circuit in Summit Point, WV, with validation 

testing conducted by the U.S. Department of 

Transportation Volpe National Transportation Systems 

Center. For verification and validation testing, the team 

used an RSU with a connection to CARMA Cloud(3) to 

broadcast TCMs to approaching vehicles to communicate 

an upcoming closed‐lane section caused by weather. When 

received by a C‐ADS vehicle,(1) the TCM could be used to 

update the vehicle’s future path to change lanes and avoid 

the weather‐related closed‐lane section.

To evaluate the performance of the system, the project 

team collected data and calculated several performance 

metrics. The evaluation showed that most of the 

performance metrics were passed in all test runs, and the 

metrics that were not reliably passed still resulted in 

minimum viable performance. In general, the issues 

encountered during testing were due to vehicle control 

issues, including slower deceleration and acceleration rates 

performed by the vehicle than the rates stated in the 

desired performance metrics. Across all test runs, the 

software systems involved were able to correctly 

communicate information to each other. More specifically, 

the V2X Hub(5)‐equipped RSU with a CARMA Cloud(3)

connection was able to successfully broadcast TCMs, and 

the C‐ADS‐equipped vehicle(1) was able to receive and 

process the TCMs. This communication allowed the 

C‐ADS‐equipped vehicle to properly and safely navigate 

the road region affected by hazardous weather.

CONCLUSION

This technology’s development highlighted the challenges 

of ensuring that separate data sources accurately describe 

the coordinate frames used to generate their data and 

receivers properly interpret the data. Developing an 

approach to address disparities between satellite‐based 

maps and high definition maps from automated driving 

systems(6) is crucial for deployment. Future work could 

focus on developing more robust techniques for 

addressing spatial alignment issues or improving 

cybersecurity in CARMA Cloud(3)‐to‐CARMA Platform(4)

connections.

Additionally, future work could further explore the use of 

cellular communications to provide approaching vehicles 

with more advanced notice of an upcoming geofence.

C-ADS WITH RWM WITH A LANE CLOSURE

Standards

This technology meets the standards for the following as set by 

SAE International®:

 SAE J3216_202107TM: Taxonomy and Definitions for Terms Related 

to CDA for On‐Road Motor Vehicles.

(1)

 SAE J3016_202104TM: Taxonomy and Definitions for Terms Related 

to Driving Automation Systems for On‐Road Motor Vehicles.

(6)

CARMA Cloud 

https://github.com/usdot-fhwa-stol/carma-cloud

V2X Hub 

https://github.com/usdot‐fhwa‐OPS/V2X‐Hub

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

1 SAE International. 2020. Taxonomy and Definitions for Terms Related 

to Cooperative Driving Automation for On‐Road Motor Vehicles.

SAE J3216_202005. Warrendale, PA: SAE International. https://www.sae.

org/standards/content/j3216_202005/, last accessed October 19, 2020.

2 USDOT. n.d. “CARMA” (web page). https://its.dot.gov/cda, last accessed 

May 30, 2023.

3 FHWA. 2023. CARMA CloudSM (software). Version 4.3.0.

4 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.

5 FHWA. n.d. “V2X‐Hub” (software and configuration files in GitHub 

repository). https://github.com/usdot‐fhwa‐OPS/V2X‐Hub, last accessed 

April 13, 2023.

6 SAE International. 2018. Taxonomy and Definitions for Terms 

Related to Driving Automation Systems for On‐Road Motor Vehicles.

SAE J3016_201806. Warrendale, PA: SAE International. https://www.sae.

org/standards/content/j3016_201806, last accessed May 30, 2023.