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SAE J2735-Draft-Rev28 [issued: 11-10-08]
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This is an SAE Motor Vehicle Council draft document of the DSRC committee, subject to change.
Extremely Large Regions
Circular regions should be used to designate extremely large areas. A circle can be set as large as an entire
state or county. Setting the DE_Direction field to 0xFFFF ensures that any vehicle within the region will
consider the corresponding traveler information to be active. [Give an example here]
DCK further thoughts, Need to deal with free text in actual messages a bit more, perhaps a section on the
actual sign content itself is warranted. We want to discourage free text in general, but it will be needed for
Road and Place names. It also very likely that the basic ITIS pattern of “text” or “phrase” will be expanded
soon to cover “text”, “phrase” or “units” (an integer number value). If this occurs we will have a new and
simple way to express signage concepts like “Speed Limit 25 MPH” or “expect 10 minute delay” as ITIS
codes with a unit value of “25” or “10” between them. FYI, these two examples would be 6 and 8 bytes of
payload in the DSRC encoding system. (in free text it is 18 and 22 chars).
Annex E Traffic Probe Message Use and Operation
Probe Data Introduction
Probe Data is comprised of vehicle attribute and sensor data that is collected and sent from a vehicle OBU
to a local RSU. This data will be used to ascertain real time road, weather, and traffic conditions. The post-
processed data will be used to advise vehicles approaching the area of current conditions and suggest
appropriate action. This data is collected autonomously as vehicles are traveling along the roadway system
and sent to an RSU when applicable. The probe message developed by the SAE-DSRC Traffic and
Traveler Information Subcommittee discussed earlier in this standard, describes the payload and format of
the Probe Data Message. This Annex describes when the OBU should collect Probe Data from the
vehicle’s internal modules/sensors as well as when and how an OBU should send the data.
Probe Message Structure
A Probe Message is transmitted from a vehicle to a RSU, which contains several snapshots, as well as the
standard J2735 message header information, that is a PSID and a PSC. That is:
A Provider Service Identifier (PSID) a number that identifies a service provided by an application
and
A (Provider Service Context (PSC) which is a field associated with a PSID containing
supplementary information related to the service
The simplified structure of a probe message and snapshots is illustrated below.