Activation dry-runs and throughput simulation are the rehearsal-and-proof phase that sits between a built, commissioned Emergency Department and the moment it accepts its first real patient. Because an ED never has a quiet soft-open — it must be fully capable on its first hour — the only way to retire risk before go-live is to exercise the space, the systems, and the people against realistic clinical load and to make the decision to open on evidence rather than optimism.
Where Simulation and Dry-Runs Sit in the Activation Arc
Activation is the bridge between construction completion and clinical operations. Commissioning and Integrated Systems Testing prove that equipment works; dry-runs and simulation prove that the operation works — that staff can find supplies, that a patient can physically move from the ambulance bay to a resuscitation bay to imaging to an inpatient bed, and that the building's systems behave correctly when people use them under pressure.
The sequence typically runs:
- Substantial completion and Certificate of Occupancy from the building AHJ (per the applicable International Building Code occupancy classification — ED spaces are generally Institutional I-2 or Business B depending on sleeping/treatment configuration).
- Commissioning (Cx) and Integrated Systems Testing (IST) — building systems verified individually and in concert (covered in adjacent operational-readiness material).
- Equipment and technology installation, integration, and acceptance — medical equipment, IT, biomedical, and clinical-system interfaces.
- Tabletop walkthroughs and low-fidelity dry-runs — staff orientation to the physical plant.
- Discrete-event throughput simulation and high-fidelity mock patient days — operational proofing under load.
- Go-live readiness review and the formal decision to open.
- Cutover and first-patient go-live, followed by a stabilization period and after-action review.
Simulation is most valuable when it begins early enough to influence outcomes. Computational throughput modeling belongs in the design and programming phases — sizing treatment-bay counts, intake configuration, and imaging adjacency. Physical dry-runs belong in the final 60 to 120 days before go-live, when the space is built but change is still possible. The two are complementary: the model predicts where bottlenecks will form; the dry-run reveals whether the prediction holds in the real room.
Discrete-Event Simulation for Throughput Design and Validation
Discrete-event simulation (DES) models the ED as a network of arrivals, queues, resources, and service times. It is the analytic backbone for sizing decisions and for validating that the constructed department can meet its throughput targets before a single patient arrives.
A credible ED throughput model is driven by:
- Arrival patterns — separate streams for walk-in/ambulatory, ambulance/EMS, and (if applicable) transfers and trauma activations, each with hour-of-day and day-of-week seasonality drawn from historical census or peer benchmarks.
- Acuity mix — typically expressed through the Emergency Severity Index (ESI levels 1 through 5), because acuity drives length of stay, resource intensity, and bed-versus-vertical-care routing.
- Service times and care pathways — triage, provider evaluation, lab and imaging turnaround, treatment, disposition, and boarding intervals.
- Resources — treatment bays, resuscitation/trauma rooms, fast-track/vertical chairs, providers, nurses, techs, registration, and shared assets such as CT, point-of-care testing, and pharmacy.
- Downstream constraints — inpatient bed availability and the boarding effect, which is frequently the single largest driver of ED crowding and is invisible to any model that stops at the ED door.