The SIRI SituationExchangeDelivery element only appears when there is a service alert active for a route or stop being called on. It is used by the responses to both the VehicleMonitoring and StopMonitoring calls.
The XML below illustrates the SIRI SituationExchangeDelivery element.
<SituationExchangeDelivery>
<Situations>
<!-- One each per Service Alert -->
<PtSituationElement>
<!-- Unique ID -->
<SituationNumber>MTA NYCT_8d065d76-2813-46ee-b024-20f956232831</SituationNumber>
<!-- Information on temporal applicability of the service alert -->
<PublicationWindow>
<!-- Start time of Service Alert -->
<StartTime>2011-12-12T08:45:00-05:00</StartTime>
<!-- End time of Service Alert -->
<EndTime>2011-12-13T08:45:00-05:00</EndTime>
</PublicationWindow>
<!-- Severity of the event -->
<Severity>undefined</Severity>
<!-- Summary text -->
<Summary xml:lang="EN">The B63 is having a party!</Summary>
<!-- Long description Text -->
<Description xml:lang="EN">The B63 is having a party! (SMS)</Description>
<Affects>
<!-- Element containing VehicleJourney lines and directions -->
<VehicleJourneys>
<!-- One for each Line/Direction -->
<AffectedVehicleJourney>
<!-- GTFS Route_ID, prefixed by agency_id -->
<LineRef>MTA NYCT_B63</LineRef>
<!-- GTFS Route direction_id -->
<DirectionRef>1</DirectionRef>
</AffectedVehicleJourney>
<AffectedVehicleJourney>
<LineRef>MTA NYCT_B63</LineRef>
<!-- GTFS Opposite Route direction_id -->
<DirectionRef>0</DirectionRef>
</AffectedVehicleJourney>
</VehicleJourneys>
</Affects>
<Consequences>
<Consequence>
<!-- Service alert consequence: CANCELLED, NO_SERVICE, DISRUPTED, INTERMITTENT_SERVICE, DELAYED, DIVERTED etc -->
<Condition>altered</Condition>
</Consequence>
</Consequences>
</PtSituationElement>
</Situations>
</SituationExchangeDelivery>
</ServiceDelivery>