arXiv subjects

Anton Kleywegt

Publications and source records attributed to Anton Kleywegt.

5 recordsLinked to original sources

arXiv2026

Policies for the Operation of an Ambulance Fleet under Uncertainty based on a New Preparedness Metric

Two important decisions in the management of an ambulance fleet are ambulance selection decisions and ambulance reassignment decisions. Ambulance selection decisions determine what to do when an emergency call arrives (such as choosing what ambulance to dispatch to the emergency or putting the emergency in a queue of emergencies waiting for an ambulance to be dispatched). Ambulance reassignment decisions determine where to send an ambulance next when it has finished service for an emergency. Making good ambulance selection decisions and ambulance reassignment decisions is challenging because a decision made at a point in time affects the ability of the emergency medical service to respond to future emergencies (that are typically not known when the decision is made). We propose a new preparedness metric that quantifies the ability of the emergency medical service to respond to future emergencies. The preparedness metric can be used to make ambulance selection decisions and ambulance reassignment decisions by solving a tractable optimization problem each time that a decision has to be made. We compare the performance of the resulting method with 9 methods that have been proposed in the literature, based on data from a real emergency medical service for a large city.

math.OC↗

arXiv2025

Management and Visualization Tools for Emergency Medical Services

This paper describes an online tool for the visualization of medical emergency locations, randomly generated sample paths of medical emergencies, and the animation of ambulance movements under the control of various dispatch methods in response to these emergencies. The tool incorporates statistical models for forecasting emergency locations and call arrival times, the simulation of emergency arrivals and ambulance movement trajectories, and the computation and visualization of performance metrics such as ambulance response time distributions. Data for the Rio de Janeiro Emergency Medical Service are available on the website. A user can upload emergency data for any Emergency Medical Service, and can then use the visualization tool to explore the uploaded data. A user can also use the statistical tools and/or the simulation tool with any of the dispatch methods provided, and can then use the visualization tool to explore the computational output. Future enhancements include the ability of a user to embed additional dispatch algorithms into the simulation; the tool can then be used to visualize the simulation results obtained with the newly embedded algorithms.

cs.HC↗

arXiv2024

Estimation of Spatiotemporal Poisson Processes with Some Missing Location Data

We consider models for spatiotemporal Poisson processes with some missing location data. We discuss four models that make provision for missing location data, and their estimation. The corresponding code is available on GitHub as an extension of LASPATED at https://github.com/vguigues/LASPATED/Missing_Data. We tested our models using the process of emergency call arrivals to an emergency medical service where the emergency reports often omit the location of the emergency. We show the difference made by using models that make provision for missing location data.

stat.ME↗

arXiv2024

Operation of an ambulance fleet under uncertainty

We introduce two new optimization models for the dispatch of ambulances. The first model, called the ambulance selection problem, is used when an emergency call arrives to decide whether an ambulance should be dispatched for that call, and if so, which ambulance should be dispatched, or whether the request should be put in a queue of waiting requests. The second model, called the ambulance reassignment problem, is used when an ambulance finishes its current task to decide whether the ambulance should be dispatched to a request waiting in queue, and if so, which request, or whether the ambulance should be dispatched to an ambulance staging location, and if so, which ambulance staging location. These decisions affect not only the emergency call and ambulance under consideration, but also the ability of the ambulance fleet to service future calls. There is uncertainty regarding the locations, arrival times, and types of future calls. We propose a rolling horizon approach that combines the current decisions to be made as first-stage decisions with second-stage models that represent the ability of the ambulance fleet to service future calls. The second-stage optimization problems can be formulated as large-scale deterministic integer linear programs. We propose a column generation algorithm to solve the continuous relaxation of these second-stage problems. The optimal objective values of these second-stage continuous relaxations are used to make approximately optimal first-stage decisions. We compare our resulting dispatch policy with popular decision rules for Rio de Janeiro emergency medical service, based on data of more than 2 years of emergency calls for that service. These tests show that our proposed policy results in smaller response times than the popular decision rules.

math.OC↗

arXiv2024

LASPATED: a Library for the Analysis of SPAtio-TEmporal Discrete data

We describe methods, tools, and a software library called LASPATED, available on GitHub (at https://github.com/vguigues/) to fit models using spatio-temporal data and space-time discretization. A video tutorial for this library is available on YouTube. We consider two types of methods to estimate a non-homogeneous Poisson process in space and time. The methods approximate the arrival intensity function of the Poisson process by discretizing space and time, and estimating arrival intensity as a function of subregion and time interval. With such methods, it is typical that the dimension of the estimator is large relative to the amount of data, and therefore the performance of the estimator can be improved by using additional data. The first method uses additional data to add a regularization term to the likelihood function for calibrating the intensity of the Poisson process. The second method uses additional data to estimate arrival intensity as a function of covariates. We describe a Python package to perform various types of space and time discretization. We also describe two packages for the calibration of the models, one in Matlab and one in C++. We demonstrate the advantages of our methods compared to basic maximum likelihood estimation with simulated and real data. The experiments with real data calibrate models of the arrival process of emergencies to be handled by the Rio de Janeiro emergency medical service.

stat.ME↗