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SAE J2735-Draft-Rev29 [issued: 12-11-08]
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282 -
This is an SAE Motor Vehicle Council draft document of the DSRC committee, subject to change.
Annex G Roadside Alerting Message Use and Operation
1. Application Description
The purpose of the Roadside Alerting message is to provide warnings to a driver from either a RSU or a
PSOBU equipped vehicle such as police, fire, transportation, or ambulance vehicle which is sending data
about a nearby event of interest to travelers. This message was originally developed by the SAE ATIS
committee. It has been used by the DSRC committee in the initial published version of the standard (as an
external imported data concept), and with this edition has been brought into DSRC standard itself with
minor modifications to take advantage of the BER-DER encoding style now being used. The message
allows a sender to “strip down” the more verbose ATIS event message and send the critical content ITIS
phrase content over the DSRC WSM stack. Variations of the message, used when less urgent content is to
be sent, can be encoded over XML and sent as an IP datagram. Examples of the proper use and encoding
of this message are covered in the DSRC Users Guide documents.
2. Preconditions for operation:
The following general conditions are presumed to prevail in this application:
1
The private vehicles are equipped with active OBU.
2
There is an RSU or an incident response vehicle equipped with active PSOBU in range.
3
Both systems are active and functional.
4
Private vehicles have available it's location, speed, direction of travel (to filter content with)
3. Flow of Events
Flow of events
1
The sender (an RSU or an PSOBU) receives or creates a suitable Roadside Alert message for
transmission .
2
The sender (an RSU or an PSOBU) begins transmitting the message using the proper encoding,
channel and repetitive rate.
3
The Vehicle, which is typically a standard OBU equipped vehicle in the vicinity, receives the
message for the first time
4
The Vehicle determines whether the message is relevant (calculates its relative position to the
event and determines if a potential interference may exist). If not, no action is taken; the vehicle may be
moving away from the event, it may not apply, or it may have already been processed.
5
If an imminent interference is detected, an alarm of some type is sent to the driver's HMI. It is
assumed that vehicles will have differing levels of HMI sophistication.
6
Data updates continue as warranted and depending on the event type.
Sender Devices:
And RSU or an PSOBU