This is the ValueSet that contains all the codes in SNOMED CT Route Codes (http://hl7.org/fhir/ValueSet/route-codes) and Drug Route Of Administration Terminology (http://hl7.org/fhir/us/pq-cmc-fda/ValueSet/spl-drug-route-of-administration-terminology). E.g. what you have to deal with if you get resources containing codes in either of them