Connected Vehicle (CV) messaging helps improve road safety by delivering timely, location-based information, such as weather hazards, traffic conditions, construction impacts, and roadway restrictions, to vehicles equipped to receive standardized, secure CV messages.
However, not all transportation data shared publicly is a “CV message.” In today’s information ecosystem, agencies and partners publish a variety of roadway data feeds, including work zone and traveler information feeds, that are designed for transportation systems, mapping providers, and other applications. These feeds can be used to support situational awareness and inform downstream products, but they are not secure, authenticated vehicle-to-infrastructure messages, and vehicles should not directly act on them without validation.
This Delve provides an overview of CV messages (SAE J2735 messages like Traveler Information Messages (TIMs) and Roadside Safety Messages) and supporting roadway data feeds, such as work zone and traveler information feeds, that help communicate conditions on the road.
Roadway Data Feeds
Connected Work Zone (CWZ) Data Feeds – also known as Work Zone Data Exchange (WZDx) Data Feeds
Connected Work Zone (CWZ) information refers to standardized work zone data feeds that provide real-time details about construction activity such as lane closures, speed limit changes, and traffic shifts. CWZ data is typically shared with transportation agencies, traveler information platforms, and navigation providers to improve awareness and planning. While CWZ data is often described as “connected,” it is not inherently a secure vehicle message and is not intended to be sent directly to vehicles for automated decision-making without additional validation and security controls.
CWZ data may include:
Traffic Data Exchange (TDX) Feeds
Traffic Data Exchange (TDX) messages are standardized digital communications that allow transportation systems, vehicles, and infrastructure to share real-time traffic and roadway information. TDX messages transmit information about congestion, accidents, lane closures, weather impacts, or speed restrictions. They are part of intelligent transportation systems designed to improve safety, efficiency, and interoperability across different platforms.
TDX feeds support interoperability and situational awareness, enabling information sharing between traffic management centers, traveler information systems, and mapping providers. However, like other roadway feeds, TDX data is generally not a secure CV message, and vehicles should not directly act on it without authentication and validation. While the TDX message standard was published a while ago and contains a good format for sharing roadway data, this standard was not widely adopted and is currently being evaluated for a revamp similar to the efforts for the WZDx/CWZ data feeds.
The 511 system, which is now widely available in almost all states, offers essential information about road conditions. These data feeds deliver real-time updates about traffic, road conditions, transit, and travel services to state 511 websites and apps and have varying degrees of detail. The 511 data feeds are typically not standardized, and formats vary by state. This makes it extremely difficult for software developers and automated systems to ingest these data streams of traveler information provided by state and regional 511 systems in the U.S. Although 511 feeds can be an essential source of public roadway information, they are not secure, authenticated connected vehicle messages, and therefore should not be treated as direct vehicle-control inputs.
Connected Vehicle Messages (Standardized SAE J2735)
Traveler Information Messages (TIMs)
TIMs are geofenced Connected Vehicle messages based on the SAE J2735 standard. TIMs can be broadcast by roadside units (RSUs), over the cellular network using Virtual RSUs (vRSUs), or through the Situation Data Exchange (SDX) and are intended for vehicles and applications designed to receive CV messages. TIMs enhance safe and efficient travel on roadways by providing real-time updates to drivers regarding various road conditions, including the following:
Traffic conditions: Congestion, incidents, or road closures.
Weather alerts: Adverse weather conditions that may affect driving or even cause road closures.
Construction updates: Road work that may affect travel routes, such as changes to speed limits or available lanes.
Travel times: Estimated travel durations for specific routes.
Emergency alerts: Notifications about natural disasters, severe weather warnings, or other emergencies that could impact road safety.
Roadside Safety Messages (RSMs)
RSMs are standardized CV messages that can be broadcast from RSUs, vRSUs, and through the SDX to connected vehicles, providing real-time information about road conditions, hazards, and safety-critical events. They are part of the U.S. Department of Transportation’s connected vehicle messaging framework, designed to improve roadway safety and efficiency. While RSMs are intended to eventually replace the TIM as they provide a more detailed description of the roadway and event message, they are not currently widely supported by Onboard Unit manufacturers. The messages include the following information:
Work zone alerts: Lane closures, detours, or reduced speed limits.
Traffic control information: Signal phase and timing (SPaT), stop signs, or yield instructions.
Hazard warnings: Slippery roads, debris, or accidents ahead.
Speed advisories: Dynamic speed limits based on conditions.
Pedestrian/bicycle safety: Notifications about crosswalk activity or vulnerable road users nearby.
Questions About Connected Vehicle Messages?
Connect with our Technology Services & Solutions Team to learn more about the applications of various CV messages.
