United States Department of Transportation logo SAE logo

SAE J2735 - Dedicated Short Range Communications (DSRC) Message Set Dictionary

This Fact Sheet was written on Sept 25, 2009 using the December 2006 Version 1.0 of the standard. The status of the standard at the time was: Published with Version 2.0 under development.

This Fact Sheet was written on September 25, 2009. The status of the standard at the time was: In Ballot.

This Fact Sheet was last verified on September 25, 2009


Standards for dedicated short range communication (DSRC) are intended to meet the requirements of applications that depend upon transferring information between vehicles and roadside devices as well as between vehicles themselves. Typically, this type of communication occurs between moving vehicles entering a communications zone with fixed roadside communication equipment or directly between moving vehicles. DSRC provides the foundation for a variety of applications including vehicle safety, emergency vehicle notification, automated tolling, enhanced navigation, traffic management and many others.

What are these standards for?

The purpose of this standard, SAE J2735 - Dedicated Short Range Communications (DSRC) Message Set Dictionary, is to support interoperability among DSRC applications through the use of standardized message sets, data frames and data elements. This standard provides information that is useful in understanding how to apply the various DSRC standards, along with the message sets, data frames and data elements, to produce interoperable DSRC applications.

Who uses them?

This standard, SAE J2735 - Dedicated Short Range Communications (DSRC) Message Set Dictionary, is intended for application developers, equipment manufacturers and system integrators in particular those involved with the Intellidrive program.

How are they used?

This standard, SAE J2735 - Dedicated Short Range Communications (DSRC) Message Set Dictionary, supports interoperability among DSRC applications. The message sets specified in this SAE Standard depend upon the lower layers of the DSRC protocol stack to deliver the messages from applications at one end of the communication system (for example, in a vehicle) to the other end (for example, a roadside equipment device). These lower layers of the DSRC protocol stack are defined and specified in standards developed by other Standards Development Organizations (SDOs). In particular, the lower layers are addressed by IEEE P802.11p, and the upper layer protocols are covered in the IEEE P1609 series of standards. The DSRC family of standards developed by the various SDOs are meant to operate together in a harmonious fashion. The message sets specified in this standard define the message content delivered by the communication system at the application layer. This standard therefore defines the message payload at the physical layer.


This standard, SAE J2735 - Dedicated Short Range Communications (DSRC) Message Set Dictionary, specifies standard message sets, data frames and data elements for use by applications intended to utilize the 5.9 GHz Dedicated Short Range Communications for Wireless Access in Vehicular Environments (DSRC/WAVE), referenced in this document simply as "DSRC", communications systems. The scope is limited to specifying initial representative message structures and data elements and providing sufficient background information to allow readers to properly interpret the DSRC standards and message definitions from the point of view of an application developer.

The standard defines message formats for an a la carte message, basic safety message, emergency vehicle alert message, generic transfer message, a probe vehicle data message and a common safety request message. The a la carte message is composed entirely of message elements determined by the sender, allowing for flexible data exchange. The basic safety message contains vehicle safety-related information that is periodically broadcast to surrounding vehicles.The emergency vehicle alert message is used for broadcasting warnings to surrounding vehicles that an emergency vehicle is operating in the vicinity. The generic transfer message provides a basic means to exchange data across the vehicle - roadside interface. The probe vehicle data message contains status information about the vehicle o enable applications that examine traveling conditions on road segments. The common safety request message is used when a vehicle participating in the exchange of the basic safety message can make specific requests to other vehicles for additional information required by safety applications.

The standard provides several informative annexes that give background on message framework, the use of various fields within the messages, expected latency and priority for various message types. These appendices illustrate the use of the messages and are not intended to be prescriptive. The first appendix covers operation with the vehicle safety message including intersection collision warning, emergency electronic brake lights, pre-crash sensing, cooperative forward collision warning, left turn assistant, stop sight movement assistance and lane change warning. The second appendix covers traffic probe message use and operation including probe snapshot information, probe data message sets, sending probe data message sets to an RSE, probe data message sets received by an RSE, vehicle anonymity, probe data security, vehicle-based data lifecycle and probe data message management. The third appendix covers the emergency vehicle approaching warning scenario which provides warning to drivers in the vicinity of a public safety vehicle that there may be potential interference between the vehicles. The last appendix covers the use of the message dispatcher which allows the flexibility of reducing, extending and reconfiguring message contents.

While not normative information, these appendices provide background in how applications are intended to operate within the DSRC environment and are thus a valuable resource for engineers and applications designers building DSRC applications.

Related documents

The following ITS standards are related and should be considered when using this standard:

The following set of standards and documents, while not part of the ITS standards, should also be considered when using this standard:

How to obtain Standards
Society of Automotive Engineers