4.2 Multi-Incident Call Stacking & Queue Management
Key Takeaways
- Call stacking holds lower-priority calls in an ordered CAD (Computer-Aided Dispatch) queue while higher-priority work is handled first, rather than handling calls strictly in arrival order.
- Unit stacking (assigning multiple resources to one large incident) is a distinct skill from call stacking (sequencing multiple separate incidents) — CritiCall tests both.
- New information re-ranks a queued call to its current tier immediately; the call does not keep its original, lower-priority queue position.
- Pre-emption means a newly arrived higher-tier call interrupts work already underway on a lower-tier one — this is expected, not an error.
- Deconfliction (checking whether a unit is already assigned before sending another) prevents wasted coverage elsewhere in the queue.
Why Call Stacking Is Tested
CritiCall almost never tests decision-making with a single, isolated incident — its scenarios routinely stack two, three, or more calls on top of each other in a short window, mirroring what a real communications center looks like on a busy shift. This section builds directly on the triage ladder from the previous section: once you can rank individual calls, call stacking is the skill of managing the queue those rankings create, and re-managing it as new calls and new information arrive.
Core Terms
Call stacking is the practice of holding lower-priority calls in an ordered, pending queue while a dispatcher (or the available field units) works through higher-priority work first, rather than handling every call the instant it rings in. The ordered list itself — every incident that has been taken but not yet fully resourced — is the queue, and it is almost always managed inside a Computer-Aided Dispatch (CAD) system, the software platform dispatchers use to log calls, track unit status, and assign resources.
Stacking is not the same as unit stacking (sometimes called resource stacking): assigning multiple field resources to a single incident because one unit cannot handle it alone. A structure fire with people trapped needs an engine, a ladder truck, and an ambulance dispatched together as an "alarm assignment," not one unit sent to investigate before backup is called. Confusing the two is a common test trap: stacking calls means sequencing separate incidents; stacking units means sizing up one incident correctly.
Two more terms matter for reordering an active queue:
- Escalation / re-ranking — when new information changes a queued call's tier (a caller reports hearing a gunshot after the call was already logged as a lower-priority disturbance), the call must jump to its new, higher position in the queue immediately — it does not keep its original place in line.
- Pre-emption — dispatching resources to a newly arrived higher-tier call even though it interrupts work already underway on a lower-tier one. Tier 1 calls pre-empt Tier 3 and Tier 4 work in the queue by definition.
- Deconfliction — checking whether a unit is already assigned to an address or incident before sending a second one. Sending a duplicate unit to a covered call wastes coverage that could be reaching an unrelated emergency elsewhere.
- Cover unit / backup unit — an additional unit sent not because the primary unit failed, but because the incident type (an in-progress violent crime, a felony traffic stop) calls for a second set of eyes before the primary unit even arrives. Assigning a cover unit is a stacking decision made at the moment of dispatch, not an afterthought once the primary unit calls for help.
The official CritiCall preparation materials describe the underlying ability being measured here simply as the capacity to "make decisions quickly and accurately based on the rules you are provided" — call stacking is that same skill applied to a moving target, since the "rules" for a queue change every time a new call rings in or a queued call gets an update.
Queue Management Reference Table
| Situation | Correct Queue Action | Why |
|---|---|---|
| A new Tier 1 call arrives while a Tier 3 call is being worked | Stack the Tier 3 call; dispatch the Tier 1 call immediately | Severity outranks whatever was already in progress |
| A queued call receives new information that raises its tier (e.g., a caller reports a weapon after the initial report) | Re-rank it to its new position at the top of the relevant tier instantly | The queue reflects current risk, not the risk at the moment the call was first taken |
| A single incident clearly needs more than one unit (structure fire, multi-vehicle injury crash) | Assign the full resource complement the incident type requires, not a single unit | Under-resourcing a large incident costs more time than dispatching correctly the first time |
| Two units are already dispatched to the same address for the same incident | Do not send a third unit automatically; verify coverage is adequate, then release the extra unit to the queue | Duplicate dispatch strands coverage that is needed elsewhere in the queue |
| A caller with a genuine but low-severity issue is on hold for several minutes | Give a brief, honest hold-time estimate rather than silence | Callers who are told nothing are more likely to hang up and call back, adding a duplicate entry to the queue |
There is no single published maximum hold time that applies to every agency — retest policy and staffing standards vary by jurisdiction — but the operating principle tested by CritiCall is consistent: Tier 1 hold time should approach zero, while Tier 3 and Tier 4 calls can reasonably wait if the caller is told what to expect.
Worked Scenario
At 2:14 p.m. a dispatcher takes a report of a two-car crash with no injuries (Tier 3) and stacks it in the queue. At 2:15 p.m., a caller reports a residential structure fire with the family still inside (Tier 1) — this pre-empts the crash call entirely; an engine, a ladder truck, and EMS are dispatched together as a coordinated unit-stacked response. At 2:16 p.m., the original crash caller calls back to say one driver is now unconscious — this new information re-ranks the crash call from Tier 3 to Tier 1, and it is dispatched immediately rather than staying at the bottom of the queue where it was originally placed. By 2:17 p.m. the dispatcher is actively working two Tier 1 incidents simultaneously while the original property-only version of the crash call no longer exists — it has been fully superseded by the escalated version.
A dispatcher has three calls in the queue behind a Tier 1 structure fire: a fender-bender, a barking-dog complaint, and a report of a suspicious vehicle. A new call reports an armed robbery in progress. Where does the new call go?
Units Adam-3 and Adam-7 are both already en route to the same reported burglary-in-progress address. A third caller reports the identical incident from a different apartment in the same building. What is the correct action?