Table 1.

Quality assessment of studies n (%)

	Yes	No	Unclear/partial
Did the study address a clearly focused question?	108 (100%)	0	0
Was the study population recruited in an acceptable way?	105 (97.2%)	0	3 (2.8%)
Did it include all the population or describe the population not included?	97 (89.8%)	7 (6.5%)	4 (3.7%)
Was the method used to calculate the distance/travel time reported accurately?	85 (81.5%)	23 (18.5%)	0
Was the health outcome accurately measured to minimise bias?	108 (100%)	0	0
Have important confounding factors been taken account of in the design or analysis?	90 (83.3%)	17 (15.7%)	1 (1%)
Is the funding source external to the organisation?	68 (63.0%)	16 (14.8%)	24 (22.2%)
Was the research peer reviewed?	101 (93.5%)	0	7 (6.5%)