This code system http://hl7.org/fhir/transport-status-reason defines the following codes:

CodeDisplayDefinition
declined-by-patient Declined by patientPatient declined transport.
refused-by-recipient Refused by recipientTransport was refused by recipient.
patient-not-available Patient not availableThe patient was not available for transport.
specimen-not-available Specimen not availableThe specimen was not available for transport.
wrong-request-data Wrong request dataWrong data in the transport request.
in-route-accident In route accidentAn accident has occurred in route.
request-not-acknowledged Request not acknowledgedThe transport request was not acknowledged.
<status value="active"/><experimental value="false"/><date value="2021-01-05T10:01:24+11:00"/><publisher value="HL7 (FHIR Project)"/><contact><telecom><system value="url"/><value value="http://hl7.org/fhir"/></telecom><telecom><system value="email"/><value value="fhir@lists.hl7.org"/></telecom></contact><description value="Status of transport."/><jurisdiction><coding><system value="http://unstats.un.org/unsd/methods/m49/m49.htm"/><code value="001"/><display value="World"/></coding></jurisdiction><caseSensitive value="true"/><valueSet value="http://hl7.org/fhir/ValueSet/transport-status-reason"/><content value="complete"/><concept><code value="declined-by-patient"/><display value="Declined by patient"/><definition value="Patient declined transport."/></concept><concept><code value="refused-by-recipient"/><display value="Refused by recipient"/><definition value="Transport was refused by recipient."/></concept><concept><code value="patient-not-available"/><display value="Patient not available"/><definition value="The patient was not available for transport."/></concept><concept><code value="specimen-not-available"/><display value="Specimen not available"/><definition value="The specimen was not available for transport."/></concept><concept><code value="wrong-request-data"/><display value="Wrong request data"/><definition value="Wrong data in the transport request."/></concept><concept><code value="in-route-accident"/><display value="In route accident"/><definition value="An accident has occurred in route."/></concept><concept><code value="request-not-acknowledged"/><display value="Request not acknowledged"/><definition value="The transport request was not acknowledged."/></concept></CodeSystem>