Two server dynamic coverage location model under stochastic travel time

Huda Zaki Naji, Mohanad AL-Behadili*, Ferhan AL-Maliky

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


This paper describes an optimization location model that minimizes the number of two kinds of ambulances, which are; advance life support (ALS) and basic life support (BLS), while meeting the coverage requirement. The purpose of this research is to improve the performance of the emergency medical service (EMS) by developing a two-server dynamic covering location model (TS-DCL). This model is considered with realistic operating conditions for the EMS system that is solved using a developed incremental search algorithm (ISA). The TS-DCL model includes the stochastic nature of travel time in response to service, so the ambulance location model becomes more realistic. Also, the approximate hypercube model is used to determine the dependence of ambulance busy fractions. An experimental study is carried out to examine the effects of the proposed model on the design of the ambulance services system. It is also including the application of the proposed model to a 144-node problem representing Al-karkh District in Baghdad City in Iraq. The experimental study shows that the TS-DCL model requires at least 26 ALS, 12 BLS backups and 24 BLS ambulances to meet the 95% coverage requirement of both the critical and non-critical calls.

Original languageEnglish
Article number19
Number of pages19
JournalInternational Journal of Applied and Computational Mathematics
Issue number1
Early online date13 Jan 2021
Publication statusPublished - 1 Feb 2021


  • Ambulance location model
  • Approximate hypercube model
  • Multi-server problems
  • Stochastic travel time
  • Tabu search algorithm


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