Table 2.

Assumptions of GIS calculations and the three delay framework, including factors which complicate modeling and examples of delays which current models generally do not account for

Assumption	Three Delay framework	Potential difficulties in measurement	Example of unaccounted delay
Patients will decide to seek care directly when need arises	First delay	Patient and disease specific	Securing funds for travel and/or care
Patients can start their travel right away	Second delay	Highly context and patient specific	Waiting for transport, e.g., ambulance or private
Patients can travel at declared speed	Second delay	Context specific	Poor road conditions, using slower modes of transport
Patients choose the fastest route	Second delay	Depends on setting, referral system	Travels another route, e.g., via lower tier hospital
Upon arrival, there is capacity to take care of patient	Third delay	Costly, may vary depending on time of day	No surgeon on site, overfilled ER

Note that GIS is used to quantify the second delay