Exploring optimal air ambulance base locations in Norway using advanced mathematical modelling.
Helicopter emergency medical services are an important part of many healthcare systems. Norway has a nationwide physician staffed air ambulance service with 12 bases servicing a country with large geographical variations in population density. The aim of the study was to estimate optimal air ambulance base locations.



We used high resolution population data for Norway from 2015, dividing Norway into >300 000 1 km×1 km cells. Inhabited cells had a median (5-95 percentile) of 13 (1-391) inhabitants. Optimal helicopter base locations were estimated using the maximal covering location problem facility location optimisation model, exploring the number of bases needed to cover various fractions of the population for time thresholds 30 and 45 min, both in green field scenarios and conditioning on the current base structure. We reanalysed on municipality level data to explore the potential information loss using coarser population data.



For a 45 min threshold, 90% of the population could be covered using four bases, and 100% using nine bases. Given the existing bases, the calculations imply the need for two more bases to achieve full coverage. Decreasing the threshold to 30 min approximately doubles the number of bases needed. Results using municipality level data were remarkably similar to those using fine grid information.



The whole population could be reached in 45 min or less using nine optimally placed bases. The current base structure could be improved by moving or adding one or two select bases. Municipality level data appears sufficient for proper analysis.
Department of Health Studies, University of Stavanger, Stavanger, Norway.|Department of Research, Norwegian Air Ambulance Foundation, Drøbak, Norway.|Department of Biostatistics, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway.
Jo
J
Røislien
Delft Institute of Applied Mathematics, Delft University of Technology, Delft, The Netherlands.
Pieter L
PL
van den Berg
Department of Research, Norwegian Air Ambulance Foundation, Drøbak, Norway.|SAFER (Stavanger Acute Medicine Foundation for Education and Research) and Stavanger University Hospital, Stavanger, Norway.
Thomas
T
Lindner
Department of Research, Norwegian Air Ambulance Foundation, Drøbak, Norway.|Department of Global Public Health and Primary Care, University of Bergen, Bergen, Norway.
Erik
E
Zakariassen
Delft Institute of Applied Mathematics, Delft University of Technology, Delft, The Netherlands.|Centrum Wiskunde & Information, Amsterdam, The Netherlands.
Karen
K
Aardal
Delft Institute of Applied Mathematics, Delft University of Technology, Delft, The Netherlands.|Centrum Wiskunde & Information, Amsterdam, The Netherlands.
J Theresia
JT
van Essen
D017732:Air Ambulances / Q000706:statistics & numerical data; D017598:Efficiency, Organizational; D004632:Emergency Medical Services / Q000592:standards / Q000706:statistics & numerical data; D005843:Geography; D006297:Health Services Accessibility; D006302:Health Services Research; D006801:Humans; D008962:Models, Theoretical; D009664:Norway; D013997:Time Factors; D014187:Transportation of Patients / Q000592:standards*