Study IV

Study IV · Peer-reviewed publication · BMC Medical Informatics and Decision Making

Response-time variability

A machine learning-based analysis of how workload, priority, geography, weather, call handling, travel, and resource availability shape EMS response times.

Study profile

Response time as emergent system behaviour

The study examines EMS response time as a systems metric shaped by interacting operational, environmental, geographic, and priority-related factors.

  • Article: Hill P, Lederman J, Jonsson D, Bolin P, Vicente V. Understanding EMS response times: a machine learning-based analysis. BMC Medical Informatics and Decision Making. 2025;25:143.
  • DOI: 10.1186/s12911-025-02975-z.
  • Design: Retrospective observational study using feature engineering, linear regression and exploratory machine learning.
  • Participants/data: Over one million EMS missions in Stockholm, Sweden, 2017–2022.
  • Outcome: EMS response time, defined as the interval from EMCC call receipt to first EMS arrival at scene.
  • Methods: Gradient boosting and related models were used to explore how call handling, travel time, priority, geography, weather, and workload interact.
  • Key contribution: Response time is interpreted as emergent system behaviour rather than a simple function of distance or urgency.
Core findings

Why response time varies across the EMS system

Multiple drivers interacted

Response time was shaped by call priority, workload, geography, weather, call handling, travel time, and resource availability rather than by any single determinant.

Priority changed system behaviour

High-priority calls were protected differently from lower-priority calls, showing how allocation rules redistribute delay across priority groups.

Tail delays matter

Lower-priority response-time distributions showed long-tail delay patterns, supporting governance approaches that look beyond averages and median targets.

Scientific contribution

From response-time target to system diagnosis

Study IV supports a shift from single-point response-time benchmarking toward distribution-aware EMS governance.

The study shows that response time reflects the interaction between clinical priority, system strain, geography, weather, and operational intervals. This makes response time useful as a systems signal, but risky as a simplistic performance target if variability and tail delays are ignored.

Response-time variability Workload Geography Weather Tail delays

Interpretation note

This study is observational and explanatory. It supports system understanding and governance of response-time variability, but it should not be interpreted as a directly deployable real-time prediction system. Operational use would require prospective validation, integration with live data streams, human-factors design, and governance safeguards.