Transferable Development Rights – A system that allows landowners in some zone districts to transfer some or all development potential from one property (a “sending” site) to another property (a designated “receiving” site). TDR’s can be used either to: Increase house size, or obtain development right within a UGB (Urban Growth Boundary). In Pitkin County, each TDR is equal to a maximum of 2,500 square feet of floor area.