Functions in the regulation of endosome morphology and late endosome formation. Has a role in controlling trafficking from early to late endosomes and from late endosomes to lysosomes. Important for localization of Gdi to the endosomal membranes. May function in controlling the activity of multiple regulators in the endocytic pathway, perhaps by positively controlling those involved in the early steps of endocytosis such as Rab5 and hrs, and negative regulating those involved in the late stages of endocytosis like car and VhaSFD. Interacts with Gdi (Rab GDP dissociation inhibitor). In ovaries, expressed both in the germ line cells and in the overlying somatic follicular epithelium. The FYVE-type zinc finger domain is necessary and sufficient for endosome targeting and localization to the plasma membrane. No visible phenotype. No effect on the subcellular localization or expression of Rab7, Rab11 and Avl. The name 'rush hour' derives from the overexpression phenotype which displays a disruption to endosomal trafficking and cargo progression.