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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.
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.
5.13 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 MSG_MapData message (which conveys a full geometric layout of the
intersection in question) 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.
The current signal preemption and priority status values (when present or active) are also sent. A more
complete summary of any pending priority or preemption events can be found in the Signal Status
message.
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 SignalState OPTIONAL,
-- the active priority state data, if present
prempt SignalState OPTIONAL,
-- the active preemption state data, if present
... -- # LOCAL_CONTENT
}
XML Representation:
<xs:element name="sPAT" type="SPAT"/>
<xs:complexType name="SPAT" >
<xs:sequence>
<xs:element name="msgID" type="DSRCmsgID" />
<xs:element name="name" type="DescriptiveName" minOccurs="0"/>
<xs:element name="id" type="IntersectionID" />
<!-- this provided a uniq mapping to the
intersection map in question
which provides complete location
and appoach/move/lane data -->
<xs:element name="status" type="IntersectionStatusObject" />
<!-- general status of the controller -->