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SAE J2735-Draft-Rev26 [issued: 09-18-08] 
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This is an SAE Motor Vehicle Council draft document of the DSRC committee, subject to change.
         <xs:element name="localSignalControlZone" type="local:SignalControlZone"
minOccurs="0"/>
      </xs:sequence>
</xs:complexType>
Used By: This entry is used directly by one other data structure in this standard, a DF called
DF_Intersection <ASN> <XML>.   In addition, this item may be used by data structures in other ITS
standards.
Remarks: Note that both a preempt to a signal system and a priority for a signal system are described in
the same terms here. The term signal control zone was created to cover both uses. 
6.40 Data Frame: DF_SignalRequest
Use: The SignalRequest is used (as part of a request message) to request either a priority or a preemption
service from a signalized intersection. It relates the intersection ID as well as the specific request (a value
of 0~7 for the request and a value of 0~7 for the strategy requested - both in the SignalReqScheme data
element).  Additional information includes the approach and egress values or lanes to be used.  
ASN.1 Representation:
SignalRequest ::= SEQUENCE {
   -- the regionally unique ID of the target intersection
   id     IntersectionID,  --  intersection ID
   
   -- Below present only when canceling a prior request
   isCancel   SignalReqScheme OPTIONAL,  
   
   -- In typical use either a SignalReqScheme 
   -- or a lane number would be given, this
   -- indicates the scheme to use or the
   -- path through the intersection
   -- to the degree it is known.
   -- Note that SignalReqScheme can hold either
   -- a preempt or a priority value.
   requestedActon  SignalReqScheme OPTIONAL,  
                           --  preempt ID or the
                           --  priority ID 
                           --  (and strategy) 
   inLane      LaneNumber OPTIONAL,       
                           --  approach Lane
   outLane     LaneNumber OPTIONAL,       
                           --  egress Lane
   type        NTCIPVehicleclass
                           --  Two 4 bit nibbles as: 
                           --  NTCIP vehicle class type
                          
--  NTCIP vehicle class level
   
   -- any validation string used by the system
   codeWord    CodeWord OPTIONAL,
   ...
   }
XML Representation:
<xs:complexType name="SignalRequest" >
      <xs:sequence>
         <!-- the regionally unique ID of the target intersection -->
         <xs:element name="id" type="IntersectionID" />
         <!-- intersection ID
         Below present only when canceling a prior request -->
         <xs:element name="isCancel" type="SignalReqScheme"  minOccurs="0"/>
         <!-- In typical use either a SignalReqScheme
         or a lane number would be given,  this
         indicates the scheme to use or the
         path through the intersection
         to the degree it is known.
         Note that SignalReqScheme can hold either
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