【正文】 range from j (catchment Cj). 1b. Compute the supply to demand ratio within Cj: 2a. For each demand location i, search all supply locations j within the travel time range from i (catchment Zi). 2b. Sum up the supply to demand ratios at these supply locations: ???jCkkjj PSR /? ??? ????i ji Zj CkkjZjji PSRA )/(Generalizing “distance decay” ? as a continuous function ? a power or exponential function ? a Gaussian function ? as a discrete variable ? dichotomous as in 2SFCA ? multiple as in E2SFCA ? a hybrid approach ? a kernel density function ? a threezone approach Generalizing “distance decay” Validation ? Modeling actual supplydemand interactions ? Individual travel behavior ? Aggregated travel pattern Optimization ? Towards equal accessibility ? Formulated as a planning problem ? minimizing accessibility gaps among demand locations by adjusting the amounts of supplies at given supply locations. A Quadratic Programming Approach ? Subject to ? ?? ???minj jijj aVdS1 12)(m in???S 1 ? S 2 ? ... ? S n ? S???? mkkjkj dDV1?where Value of optimization ? Emphasizing the equality issue ? Identifying over and undercapacity of supply ? Guiding planning and public policy in closing the gap Application in Healthcare Access: HPSA designation ? . ranks behind in health performance ? deep disparities in access to care and health outes ? Federal programs: MUP amp。Integr ated D esign ationL e g e n dP oor Spat ial Ac c e s sM ar gian l Spat ial Ac c es s and H igh N e edsP oor Soc ioec onom ic St a t usM ar gina l Soc ioec ono m ic St at u sa nd Soc ioC ult ural Bar r ierC ou nt y Boun d ary( Sp a t i a l a c ce ss c ri t e ri a : sc o r e 1 / 3 5 0 0 o r