A narrative analysis of the 2SFCA and i2SFCA methods

Examining the impact of COVID-19 vaccination rates on differential access to critical care

“…Three different accessibility models are used here to estimate congestion levels at hospitals and the difference in the supply and cost accessibility differences between the two at-risk groups – the ABFCA ( Lin & Cromley, 2021 ), the CSA ( Lin & Cromley, 2021 ), and the RAAM ( Saxon & Snow, 2020 ). These models were chosen because they explicitly use congestion in some manner to estimate accessibility.…”

“…By comparing these three methods, one can better interpret results than from an individual method and gauge the sensitivity of the results with respect to these models. In the ABFCA, the probability that the at-risk population at will be allocated to the hospital, , is modified from that of the BFCA ( Páez et al, 2019 ) by adding the attraction of a facility into the calculation ( Lin & Cromley, 2021 ): where, is the number of ICU beds at the j th hospital and is the impedance factor defined in Equation (1) . This probability is then used to calculate the flow of patients to each hospital and Wang's (2018) congestion (or crowdedness) index, , for the service center: …”

“…He constructed a modified version (the M2SFCA) to address the issue of how interaction is discounted over distance. Lin and Cromley (2021) noted that Delamater's concern could be eliminated by recognizing that accessibility is a bivariate concept, and there is a distinction between supply accessibility (amount of resources per unit of demand) and cost accessibility (average cost of acquiring those resources per unit of demand).…”

“…The BFCA has been used to measure spatial access to healthcare during the COVID-19 pandemic in Brazil ( Pereira et al, 2021 ). Lin and Cromley (2021) modified the BFCA to create the adjusted BFCA (ABFCA) by using the i2SFCA is in the first stage to calculate service-provider ratios for estimating accessibility in a second stage. However, even though congestion is used to estimate accessibility based on congestion levels, congestion was not used in selecting service providers.…”

“…However, even though congestion is used to estimate accessibility based on congestion levels, congestion was not used in selecting service providers. However, Lin and Cromley (2021) used congestion levels as part of the attractiveness of the hospitals in conjunction with their overall supply level in a congested supply accessibility (CSA) model. Finally, an alternative approach to 2SFCA models was proposed by Saxon and Snow's (2020) ; their rational agent accessibility model (RAAM) measures accessibility as a trade-off between congestion and movement cost.…”