Glossary

Plain-language meanings of the terms used in this guide.

Written for: Intermediate Coder Confident Coder Decision-makers Domain experts General public

automated tests: Checks, run on request by the developers, that confirm the model still behaves as expected.
callsign: The radio name of a vehicle on duty, such as H70 (a helicopter) or CC72 (a car).
crew group (callsign group): Vehicles that share one crew, such as helicopter H70 and car CC70; only one can be out at a time.
critical care (CC): The highest level of pre-hospital care the service provides; one of the three care categories in the model.
enhanced care (EC): A level of care above standard ambulance care but below critical care.
helicopter benefit: Whether a patient would gain from a helicopter rather than a car, for example for speed or access.
historical baseline: Model results using the rotas that actually ran in the past, used to check the model against reality.
hosted site: A copy of the web app running on an outside service, reachable in a browser without installing anything.
learned patterns (fitted distributions): Mathematical descriptions of past data, such as how long time on scene usually takes, which the model draws from.
missed job: A call for which no air ambulance vehicle was free and suitable at the time, so none was sent.
open-source licence: The terms under which the code can be used and changed; this project uses GPL-3.0.
parameter template: An Excel workbook the user fills in to describe a scenario and upload to the web app.
random seed: A starting number that fixes the random chances, so the same seed and settings give the same results again.
regular job (REG): A job not identified as needing critical or enhanced care.
rota: The table of which vehicles are on shift at which hours, with separate summer and winter hours.
run (replication): One complete play-through of the simulated period. The model does many runs, each with different random chances, and averages them.
scenario: A set of settings (rota, fleet, servicing, demand) to test.
servicing: Planned maintenance that takes an aircraft out of use for several weeks.
short-notice (ad hoc) unavailability: Times a helicopter cannot fly although on shift, for example due to weather or crew issues.
simulation: A computer model that imitates a real service over time, so that changes can be tried out safely.
the call simulator: The part that creates each day’s made-up calls and patients and plays out each job step by step.
the dispatch rules: The part that decides which vehicle, if any, goes to each call.
the fleet and rota model: The part that represents each helicopter and car, its shift hours and its servicing dates.
the historical data preparer: An occasional, separate step that turns real job records into the patterns and summaries the model uses.
the pattern sampler: The part that holds patterns learned from past jobs and draws realistic values from them.
the results and comparison tool: The part that turns run records into figures and charts and compares them with real past performance.
the run manager: The part that repeats the model many times with different random chances and combines the results.
the web app: The set of web pages where users choose a scenario, run the model and view the results.
utilisation: The share of a vehicle’s on-shift hours spent on jobs.