Cilium-specific protein required to control the microtubule- based, ciliary axoneme structure. May act by maintaining the association between IFT subcomplexes A and B. Binds GTP but is not able to hydrolyze fit; the GTPase activity remains unclear. Required to pattern the neural tube. Involved in cerebral cortex development: required for the initial formation of a polarized radial glial scaffold, the first step in the construction of the cerebral cortex, by regulating ciliary signaling. Regulates the migration and placement of postmitotic interneurons in the developing cerebral cortex. Plays a role in ciliar trafficking of phosphatidylinositol phosphatase INPP5E in ciliogenesis (PubMed:38219074). May regulate ARF6- and RAB22A- dependent endocytic recycling traffic (PubMed:23223633). {ECO:0000269|PubMed:23150559, ECO:0000269|PubMed:23223633, ECO:0000269|PubMed:38219074}. This is the function of ARL13B (ARF like GTPase 13B, ENSG00000169379).