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SAE J2735-Draft-Rev26 [issued: 09-18-08]
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39 -
This is an SAE Motor Vehicle Council draft document of the DSRC committee, subject to change.
<!-- the message and sub-message type, as
defined in the RTCM revision being used
NOTE as the message type is also in the payload,
we may want to remove it from here, not sure right now. DCK -->
<xs:element name="wdCount" >
<xs:simpleType>
<xs:restriction base="xs:unsignedShort">
<xs:maxInclusive value="1023"/>
</xs:restriction>
</xs:simpleType>
</xs:element>
<!-- a count of bytes to follow -->
</xs:sequence>
</xs:complexType>
In addition, this item may be used by data structures in other ITS standards.
Remarks: Observe that the transport layer details (preamble, CRC, etc.) as outlined in RTCM standard
10403.1 version 3.0 clause four are not sent in this message. In a similar fashion, the same framing
information found in clause 4.2 of the RTCM standard 10402.3 (version 2.3) is not sent. These would be
reconstituted after reception by a mobile device and before sending the resultant message to any positioning
device expecting messages in such a format, as outlined in the RTCM recommendations found in clause
four of each document. Also observe that the specific bit ordering of the transport message level used in the
final message varies between RTCM version 3.x and that of version 2.3.
5.14 Message: MSG_SignalPhaseAndTimingMessage (SPAT)
Use: The Signal Phase and Timing (SPAT) message is used to convey the current status of a signalized
intersection. Along with the _working term_ MSG_MapFragment data frame (which conveys a full
geometric layout of the intersection) the receiver of this message can determine the state of the signal
phasing and when the expected next phase will occur.
The SPAT message sends the current movement state of each active phase in the system as needed (values
of what lights are active and values of for what durations the light is expected to continue). The state of un-
active movements (typically all red) is not normally transmitted. Movements are mapped to specific lanes
and approaches by use of the lane numbers present in the message. These lane numbers correspond to the
specific lanes described in the MAP message for that intersection.
Signal preemption and priority status values (when present or active) are also sent.
ASN.1 Representation:
SPAT ::= SEQUENCE {
msgID DSRCmsgID,
name DescriptiveName OPTIONAL,
id IntersectionID,
-- this provided a uniq mapping to the
-- intersection map in question
-- which provides complete location
-- and appoach/move/lane data
status IntersectionStatusObject,
-- general status of the controller
lanesCnt INTEGER(1..255) OPTIONAL,
-- number of states to follow (not always
-- one per lane because sign states may be shared)
states SEQUENCE (SIZE(1..255)) OF MovementState,
-- each active Movement/lane is given in turn
-- and contains its state, and seconds
-- to the next event etc.
priority SEQUENCE (SIZE(1..7)) OF
SignalState OPTIONAL,
-- all active priority state data
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