The current O/D data from Seoul(1997) is based on the unit of dong, an administrative unit
under gu, for example Kangnam-gu, however, dong is a too large to analyze the transport
demand forecast, because it comprises many blocks where can have multiple stations of a new
transit. To build O/D data corresponding to new transit stations, sub-zone division is
necessary. It will distinguish the trips occurring within a dong. The 26 dongs are, thus,
divided into 216 sub sections based on tong, a sub administrative unit under a dong, and
future O/D data of each tong is produced using forecast regression equation of generation by
trip purposes, as suggested by SDI(1998b). The future socio economic indices used as
independent variables in regression are revised as present indices of each dong. Sub-zone
division program is composed in C++ language, because it is beyond Excel to transfer the
existing Seoul O/D data having more than 1,000 zones, into that of 256 columns. The sub
division diagram is shown below in figure 2.