Comparing alternative approaches to measuring the geographical accessibility of urban health services: Distance types and aggregation-error issues

Table 4 Spearman rank correlations between measures of the accessibility of hospitals by aggregation method

		Accessibility measures using shortest network distance			Accessibility measures using shortest network time
Hospitals		CTC^a	WDA^b	WBl^c	CTC^a	WDA^b	WBl^c
Minimum network distance	CTC^a	1.000			1.000
	WDA^b	0.991	1.000		0.987	1.000	0.997
	WBl^c	0.989	0.997	1.000	0.984	0.997	1.000
Average distance to three closest services	CTC^a	1.000			1.000
	WDA^b	0.997	1.000		0.995	1.000
	WBl^c	0.997	0.999	1.000	0.994	0.999	1.000
Average distance to five closest services	CTC^a	1.000			1.000
	WDA^b	0.998	1.000		0.996	1.000
	WBl^c	0.998	0.999	1.000	0.995	0.999	1.000
Average distance to all services	CTC^a	1.000			1.000
	WDA^b	0.998	1.000		0.995	1.000
	WBl^c	0.999	0.999	1.000	0.995	0.998	1.000
Number of services within 500 metres	CTC^a	1.000			1.000
	WDA^b	0.604	1.000		0.993	1.000
	WBl^c	0.588	0.838	1.000	0.992	0.999	1.000
Number of services within 1000 metres	CTC^a	1.000			1.000
	WDA^b	0.828	1.000		0.990	1.000
	WBl^c	0.776	0.924	1.000	0.990	0.998	1.000
Number of services within 2000 metres	CTC^a	1.000			1.000
	WDA^b	0.916	1.000		0.978	1.000
	WBl^c	0.898	0.968	1.000	0.976	0.996	1.000
Gravity model with α = 1	CTC^a	1.000			1.000
	WDA^b	0.994	1.000		0.992	1.000
	WBl^c	0.993	0.998	1.000	0.990	0.997	1.000
Gravity model with α = 1.5	CTC^a	1.000			1.000
	WDA^b	0.993	1.000		0.990	1.000
	WBl^c	0.992	0.996	1.000	0.988	0.996	1.000
Gravity model with α = 2	CTC^a	1.000			1.000
	WDA^b	0.991	1.000		0.987	1.000
	WBl^c	0.991	0.995	1.000	0.986	0.994	1.000

^a Aggregation method based on census tract centroid (the least accurate method).
^b Aggregation method based on the population-weighted mean of the accessibility measure for dissemination areas within census tracts.
^c Aggregation method based on the population-weighted mean of the accessibility measure for blocks within census tracts (the most accurate method).

ISSN: 1476-072X