Modeling ambulance dispatching rules for EMS

72 Pages·2016·3.18 MB·English

DEGREE PROJECT IN TECHNOLOGY,
SECOND CYCLE, 15 CREDITS
STOCKHOLM, SWEDEN 2016
Modeling ambulance
dispatching rules for EMS-
systems
LORINDE KNOOPS
TILDA LUNDGREN
KTH ROYAL INSTITUTE OF TECHNOLOGY
SCHOOL OF ENGINEERING SCIENCES

Modeling ambulance dispatching
rules for EMS-systems

L O R I N D E K N O P P S
T I L D A L U N D G R E N

Degree Project in Applied Mathematics and Industrial Economics (15 credits)
Degree Progr. in Industrial Engineering and Management (300 credits)
Royal Institute of Technology year 2016
Supervisors at KTH: Krister Svanberg, Jonatan Freilich
Examiner: Henrik Hult

TRITA-MAT-K 2016:35
ISRN-KTH/MAT/K--16/35--SE

Royal Institute of Technology
SCI School of Engineering Sciences

KTH SCI
SE-100 44 Stockholm, Sweden

URL: www.kth.se/sci

Abstract
Thisthesispresentsastudyonefficientdispatchingrulesinambulancedispatch-
ing. By efficient dispatching rules, we mean such dispatching rules that lower
responsetimesforpriority1callswhilekeepingresponsetimesforpriority2calls
at an adequate level. A Markov process and a simulation model were developed
in order to evaluate the performance of several existing and newly designed dis-
patching rules. On four different response areas, five different dispatching rules
were tested and their performances were compared. Particular focus was put
uponthedispatchrulecurrentlyusedbytheSwedishemergencyserviceprovider
SOS Alarm; the Closest rule. Our findings indicate that the four priority-based
dispatchingrulesalloutperformtheClosestruleindecreasingthemeanresponse
timeforcallsofprioritydegree1. Furthermore,implementingrestrictionsonthe
traveltimeforpriority2callswasprovenanefficientwaytocontrolthetrade-off
between the mean response time of priority 1 and 2 calls. The conclusion was
drawn that the possibilities for more efficient ambulance dispatching are many
and that SOS Alarm should consider implementing priority-based dispatching
rules, alike the ones presented in this thesis, in their dispatching process. A
study of the ambulance operator and controller profession, and the operator’s
and controller’s interplay with the decision support system used by SOS Alarm
in the ambulance dispatching process, was conducted in parallel. The properties
of the interaction dynamics between operator and automation and the dangers
linked to it were mapped out, described and analyzed.
Keywords: Ambulance dispatching, Ambulance logistics, Emergency medical
services, Priority-based dispatching rules, Markov process, Professional compe-
tencies
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Modellering av dirigerings-
strategier fo¨r EMS-system
Sammanfattning
Denna kandidatexamensuppsats behandlar effektiva dirigeringsstrategier inom
ambulansdirigering. Effektiva dirigeringsstrategier ˚asyftar dirigeringsstrategier
som lyckas s¨anka svarsstiden f¨or inkommande prioritet 1-samtal, samtidigt som
svarstiden f¨or prioritet 2-samtal h˚alls p˚a en tillfredsst¨allande niv˚a. I syfte att
utv¨arderaolikadirigeringsstrategierutveckladesb˚adeenMarkovskmodellochen
simuleringsmodell. P˚afyraolikageografiskaomr˚adentestadesochj¨amf¨ordesfem
olika dirigeringsstrategier, varav tv˚a existerande och tre nyutvecklade. S¨arskilt
fokus riktades mot Closest rule, vilket ¨ar den dirigeringsstrategi som anv¨ands i
SOS Alarms verksamhet idag. Fr˚an resultaten kunde utl¨asas att de prioritets-
baserade dirigeringsstrategierna resulterade i en l¨agre genomsnittlig svarstid f¨or
prioritet1-fall¨anClosestrule. Dessutomkonstateradesdetattenbegr¨ansningav
svarstiderna f¨or prioritet 2-samtal var ett effektivt s¨att att kontrollera balansen
mellandegenomsnittligasvarstidernaf¨orsamtalavprioritet1,respektive2. Slut-
satsen drogs att m¨ojligheterna f¨or att utveckla nya effektiva dirigeringsstrategier
¨ar m˚anga och att SOS Alarm b¨or ¨overv¨aga att implementera prioritetsbaserade
dirigeringsstrategier likt dem som presenterats i denna uppsats. Parallellt stud-
erades ambulansoperat¨orens och -dirigentens yrkeskunnande, samt operat¨orens
och dirigentens samspel med det beslutsst¨odssystem som anv¨ands i SOS Alarms
dirigeringsverksamhet. Interaktionen mellan operat¨or och automatisering samt
de relaterade riskerna kartlades, beskrevs och analyserades.
Nyckelord: Ambulansdirigering, Ambulanslogistik, Prehospital sjukv˚ard,
Prioritets-baserade dirigeringsstrategier, Markovprocess, Yrkeskunnande
iii

Acknowledgements
We would like to thank Tobias Andersson Granberg for his guidance and en-
couragement in carrying out this project work. He has been of great help in the
developmentoftheproblemformulationandinitialmodelsetting. Wewouldalso
liketoexpressourgratitudetowardsJohanWesterborn,whohelpedusrefinethe
useofMarkoviantheoryinourmodelsetting. Finally, wethankKentRing, who
receivedusattheSOSAlarmcentralinStockholmandputusinfurthercontact
with SOS Alarm operators.
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