title: Optimizing the location of ambulances in Tijuana, Mexico.
abstract: In this work we report on modeling the demand for Emergency Medical Services (EMS) in Tijuana, Baja California, Mexico, followed by the optimization of the location of the ambulances for the Red Cross of Tijuana (RCT), which is by far the largest provider of EMS services in the region. We used data from more than 10,000 emergency calls surveyed during the year 2013 to model and classify the demand for EMS in different scenarios that provide different perspectives on the demand throughout the city, considering such factors as the time of day, work and off-days. A modification of the Double Standard Model (DSM) is proposed and solved to determine a common robust solution to the ambulance location problem that simultaneously satisfies all specified constraints in all demand scenarios selecting from a set of almost 1000 possible base locations. The resulting optimization problems are solved using integer linear programming and the solutions are compared with the locations currently used by the Red Cross. Results show that demand coverage and response times can be substantially improved by relocating the current bases without the need for additional resources.
authors.affiliation: Posgrado en Ciencias de la Ingeniería, Instituto Tecnológico de Tijuana, Tijuana, BC, Mexico. Electronic address: juan.carlos.dibene.simental@gmail.com.
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: Dibene
authors.affiliation: Posgrado en Ciencias de la Ingeniería, Instituto Tecnológico de Tijuana, Tijuana, BC, Mexico. Electronic address: yaz.maldonado@tectijuana.edu.mx.
authors.forename: Yazmin
authors.initials: Y
authors.lastname: Maldonado
authors.affiliation: Universidad Autónoma de Baja California, Tijuana, BC, Mexico. Electronic address: cvera@eng.ucsd.edu.
authors.forename: Carlos
authors.initials: C
authors.lastname: Vera
authors.affiliation: MAE, University of California San Diego, La Jolla, CA, USA. Electronic address: mauricio@ucsd.edu.
authors.forename: Mauricio
authors.initials: M
authors.lastname: de Oliveira
authors.affiliation: Posgrado en Ciencias de la Ingeniería, Instituto Tecnológico de Tijuana, Tijuana, BC, Mexico. Electronic address: leonardo.trujillo@tectijuana.edu.mx.
authors.forename: Leonardo
authors.initials: L
authors.lastname: Trujillo
authors.affiliation: CINVESTAV-IPN, Mexico, DF, Mexico. Electronic address: schuetze@cs.cinvestav.mx.
authors.forename: Oliver
authors.initials: O
authors.lastname: Schütze
mesh_terms: D000552:Ambulances / Q000706:statistics & numerical data*; D004632:Emergency Medical Services / Q000379:methods* / Q000706:statistics & numerical data*; D040362:Geographic Information Systems; D006801:Humans; D008490:Medical Informatics; D008800:Mexico; D008962:Models, Theoretical; D012011:Red Cross
keywords: Ambulance Location Problem; Double Coverage Models; Emergency Medical Services; Integer Programming; Optimization