 |
 |
 |
 |
|
 |
 |
SAE J2735-Draft-Rev29 [issued: 12-11-08]
-
33 -
This is an SAE Motor Vehicle Council draft document of the DSRC committee, subject to change.
<xs:maxInclusive value="32"/>
</xs:restriction>
</xs:simpleType>
</xs:element>
<!-- a count of how many snaphots
type entires will follow -->
<xs:element name="snapshots" >
<xs:complexType>
<xs:sequence minOccurs="1" maxOccurs="32">
<xs:element name="snapshot" type="Snapshot" />
<!-- a seq of name-value pairs along with the space and time of the
first measurement set -->
</xs:sequence>
</xs:complexType>
</xs:element>
<xs:element name="localProbeVehicleData" type="local:ProbeVehicleData"
minOccurs="0"/>
</xs:sequence>
</xs:complexType>
Remarks: At the time of writing additional probe vehicle messages are being developed that will allow control over
what information is gathered and reported in a probe vehicle message. Builders are urged to consider these messages in
their development of products using this message.
5.8 Message: MSG_RoadSideAlert
Use: This message is used to send alerts for nearby hazards to travelers. Unlike many other messages
which use the LRMS profiles to describe the areas affected, this message likely applies to the receiver by
the very fact that it is received. In other words, it does not use LRMS. Typically transmitted over the
Dedicated Short Range Communications (DSRC) media in both WSM and XML forms, this message
provides simple alerts to travelers (both in vehicle and with portable devices). Typical example messages
would be "bridge icing ahead" or "train coming" or "ambulances operating in the area." The full range of
ITIS phrases are supported here, but those dealing with mobile hazards, construction zones, and roadside
events are the ones most frequently expected to be found in use.
This message is for the alerting of roadway hazards; not for vehicle cooperative communications, mayday,
or other safety applications (see SAE J2735 for these). It is generally presumed that each receiving device
is aware of its own position and heading, but this is not a requirement to receive and understand these
messages. Nor is having a local base map.
The space vector section of the message gives a simple (and optional) vector for where the hazard is
located (fixed or moving) and can be used to filter some messages as being not applicable. Consider a
"train approaching" message which indicates the train is in fact traveling away from the receiver. The basic
messages types themselves are represented in the standard ITIS codes send only in their integer
representation formats. This ITIS list is national in scope, never outdated (items can only be added), and in
this use does not allow local additions, refer to SAE J2540.1 for the complete code list. A priority level for
the message is also sent, which may be matched to various other priorities in the cockpit to determine the
order and type of message presentation to minimize driver distraction. Message transmission priority is
typically handled in the IEEE 1609 standard layer in the application stack and is a function of the
application type. A duration field provides a gross level for the range (distance) of applicability for the
message over distance. For example, some messages are no longer meaningful to the traveler once the
vehicle has moved a distance down the roadway link.
In many cases a complex event will also be explained in the other supporting ATIS messages (available on
DSRC service channels), and a linkage value is given in those cases when such data is available.
ASN.1 Representation:
RoadSideAlert ::= SEQUENCE {
msgID DSRCmsgID,
-- the message type.
msgCnt MsgCount,
typeEvent ITIS.ITIScodes,