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

Code Display Definition
declined-by-patient Declined by patient Patient declined transport.
refused-by-recipient Refused by recipient Transport was refused by recipient.
patient-not-available Patient not available The patient was not available for transport.
specimen-not-available Specimen not available The specimen was not available for transport.
wrong-request-data Wrong request data Wrong data in the transport request.
in-route-accident In route accident An accident has occurred in route.
request-not-acknowledged Request not acknowledged The 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>