This page describes a decision-support path from probe ingestion to a staging record a person accepts. It is not an autonomous reefer dispatcher, and it is not legal advice.
This note is for carriers and brokers who already run refrigerated trailers and want the dispatch decision to see temperature evidence before a tender is accepted. It does not certify a load, replace a shipper specification, or tell a unit how to run. Any minute, degree, or dollar figure below is illustrative and must be replaced by the carrier's own policy, the shipper's written instructions, and the refrigeration manufacturer's guidance.
- Pre-cool, setpoint, and pulp temperature are three different facts. Storing them in one column makes the board lie.
- The accept action stays disabled until pre-cool is confirmed by a probe reading, or a named dispatcher overrides with a reason.
- Every probe row carries a stable probe id, an offset timestamp, an explicit unit, GPS age, and power status.
- A stale probe, missing pre-cool confirmation, or a door left open after pre-cool aborts the stage.
- The calculation writes a staging record a dispatcher accepts. It never sets a dispatched status.
Pre-cool, setpoint, and pulp temperature
Pre-cool, setpoint, and pulp temperature are three different facts, and a dispatch system that stores them in one column will lie. The setpoint is the commanded target on the refrigeration microprocessor. A frozen protein program might be set near 0 F, and a chilled produce program might be set near 34 F. Those numbers are instructions to the unit. They say nothing about whether the walls, floor, ceiling, or return air are actually at that temperature. A unit can display the correct setpoint while it is powered off in a yard, while it is in a defrost cycle, or while it has been running for only a few minutes after a washout.
Pre-cool is the empty-box pull-down that happens before the doors open for loading. The goal is to bring supply air, return air, and the interior surfaces close to the setpoint so the commodity does not spend the first hours fighting residual heat. Pulp temperature is a measurement in the product itself, typically taken by inserting a probe into the flesh of produce or into a representative case, using the shipper's method. Air at setpoint does not prove pulp is at setpoint. Pulp above the required band means the product is carrying heat into a box whose airflow will be restricted once the load is stacked. A predictive pre-cool estimate can suggest how long an empty trailer needs, but the confirmation the board trusts is a probe reading inside the freshness window, not the setpoint text on the load tender.
Board trusts
- A probe reading inside the freshness window
- The shipper setpoint stored apart from the commanded setpoint
- A unit stated on every row
Not proof
- Setpoint text on the load tender
- Air temperature used as a substitute for pulp
- A prior load's setpoint left on the microprocessor
Why a board that ignores box temperature accepts a load the trailer cannot protect
Most dispatch boards are built around asset availability. They show the trailer number, the last drop, the next empty time, hours of service, and sometimes the setpoint last keyed into the unit. That layout answers "which trailer can be at the dock." It does not answer "which trailer can hold this commodity." A trailer that sat in a sunny yard, came out of a warm wash bay, or was just switched from a frozen setpoint to a chilled setpoint can wear the right setpoint and still have box air many degrees above the product requirement. If the board accepts the tender on availability alone, the carrier has committed equipment that cannot protect the load during the period when the box is furthest from steady state.
The exposure is concentrated, not theoretical. Doors open at the dock, warm air enters, the product restricts the return path, and the unit needs time to recover. On a short haul the recovery window may be most of the trip. On a lane with a high afternoon ambient, a marginal box at origin becomes a rejected delivery or a claim conversation at the receiver, even when the driver did not change the setpoint. The architecture in this page refuses that acceptance path. The board may still rank trailers by location and hours, but the accept action stays disabled until pre-cool is confirmed or a dispatcher deliberately overrides with a recorded reason. An override is a human decision with a name on it. It is not a silent default.
Inputs the pre-cool decision is allowed to use
Five inputs are enough to stage a responsible pre-cool decision, and each one has a defined source. The first is the ambient forecast along the lane, not a single reading at the origin city. A corridor from a desert shipper to a high-altitude receiver can swing through a large diurnal range, and the first hours after loading are the hours that should use the warmer end of that forecast. The second is a transit duration band, expressed as a lower and upper hours figure from the carrier's own service history on that lane, not a single ETA. The band tells the dispatcher whether a slow pull-down still leaves recovery time before the first delivery. It is not a promise that the freight will arrive inside the band.
The third input is a continuous probe feed from the trailer, with a stable probe identity and a timestamp. A spot check phoned in by the driver can be noted, but it does not satisfy the feed. The fourth is door-open events with start and end, or a cumulative open-seconds field, so the board can tell a yard door left open after pre-cool from a live unload at a receiver. The fifth is the commodity setpoint on the shipper's instruction, stored separately from the setpoint currently commanded on the unit. If those two numbers disagree, the stage stops until a person reconciles them. Optional context, such as a recent washout flag or a zone identifier on a multi-temp trailer, may be attached. The model is not allowed to invent a pulp temperature, a shipper waiver, or a fuel level.
Illustrative pre-cool lead times by commodity class
Lead time is the clock the planner starts so the empty box can approach setpoint before the appointment. It depends on the temperature gap, the unit's condition, whether the trailer is on diesel or electric standby, and how the trailer was used on the prior load. A fleet that keeps completed pre-cool events, with start temperature, end temperature, and minutes of runtime, can fit its own estimate and publish an error band measured on that history. A fleet that does not have that history should use a deterministic policy table and a probe confirmation, not a model that pretends to know the unit. This page does not publish an accuracy rate, because no accuracy rate travels from one fleet to another.
The table below is illustrative. It is not a shipper specification, not a manufacturer pull-down curve, and not a safe harbor under any food safety rule. Frozen, chilled produce, and dairy are separated because their failure modes differ. Frozen loads care about a deep pull-down and about a trailer that was just hauled as a dry van. Chilled produce cares about a narrow band and about pulp, which the carrier often does not control at origin. Dairy often sits in a similar air band to produce but moves under a different shipper program and a different receiver rejection practice. Use the rows to design the policy fields, then replace every number with the carrier's own standard.
| Commodity class | Illustrative setpoint band | Illustrative empty-box pre-cool from a 70 F yard | What the board must not treat as proof |
|---|---|---|---|
| Frozen | 0 F class | 90 to 150 minutes | Setpoint text without a return-air reading in the freshness window |
| Chilled produce | 34 F class | 45 to 90 minutes | Air temperature used as a substitute for pulp temperature |
| Dairy | 34 F to 38 F class | 40 to 75 minutes | A prior load's setpoint left on the microprocessor |
The FSMA record the carrier must be able to produce
The FDA Sanitary Transportation of Human and Animal Food rule is the duty backdrop for shippers, loaders, carriers, and receivers who move food in the United States. This page is not legal advice. It does not restate the rule, and it does not decide who on a given load is the shipper or the carrier. Confirm current 21 CFR requirements with counsel before anyone treats a dispatch screen as a compliance file. What the architecture insists on is narrower: if the carrier agreed to operate under a temperature plan, the carrier should be able to produce a record of who set the point, when it was set, and what the probes showed at the moments that mattered.
Who set the point means a person or a named system account, not a shared "dispatch" login. When means a timestamp with a time zone, tied to the order and the trailer. What the probes showed means the value, the unit, the probe identity, and the age of that reading, stored so a later export does not depend on a telematics portal that rotates its history. The record should also show whether a dispatcher accepted the stage, rejected it, or overrode an abort, and the reason code for an override. Producing that packet when a shipper or an inspector asks is an operational capability. It is not, by itself, proof that the product stayed in range for the whole trip. In-transit alarms, receiver pulp checks, and the shipper's own plan remain separate controls.
The probe ingestion contract
Telematics vendors do not share one payload. The ingestion contract is the carrier's own required shape, mapped at the edge from each vendor, so the dispatch board never sees a raw feed. Every accepted row carries a probe identifier, a timestamp with an offset, an explicit temperature unit, the age of the GPS fix that was current when the temperature was sampled, and a power status. The probe identifier must survive a gateway swap. If the vendor renumbers probes, a crosswalk is applied before the row is stored, and the original vendor identifier is kept beside it. Trailer number alone is not a probe identifier, because a multi-temp trailer has more than one zone and a single trailer number would average them into fiction.
Unit is mandatory on every row. A parser must not infer Fahrenheit because a number falls between -20 and 40. Zero is both a frozen setpoint in Fahrenheit and the ice point in Celsius, and that ambiguity is how a board silently warms a load. GPS age is not probe age. A fresh temperature with a stale position can still be used for the pre-cool test, but it must not be compared to a lane ambient forecast as if the trailer location were known. Power status has to distinguish a commanded setpoint from a compressor that is actually powered, including electric standby at a dock. Unknown power is a failed row, not a blank that later code treats as on. Clock skew beyond an illustrative two minutes against the carrier's time source quarantines the row until a person looks at it.
| Field | Meaning the board requires | Illustrative fail condition |
|---|---|---|
| Probe id | Stable identity of the supply, return, or zone probe | Missing, or remapped with no crosswalk |
| Timestamp | Sample time with an explicit offset | No zone, or skew beyond about 2 minutes |
| Unit | F or C stated on the row | Unit inferred from the magnitude |
| GPS age | Age of the position fix at sample time | Older than the carrier's window, lane check held |
| Power status | On, off, standby, electric, or diesel | Unknown, or setpoint stored with the unit unpowered |
Abort rules before a load is staged
Abort means the staging record is written as blocked, not that the trailer is secretly dispatched anyway. Three aborts are non-negotiable in this design. A stale probe aborts, because the last good temperature is history, not the box now. Missing pre-cool confirmation aborts, because a setpoint without a completed empty-box pull-down is not confirmation. Door open beyond the carrier's threshold aborts when that open time falls after pre-cool complete and before the trailer is sealed for departure. A door open during a live unload is a different state and must not reuse the yard rule. The threshold itself is policy. An illustrative starting point some fleets discuss is on the order of 10 to 15 cumulative minutes, and that range is an example, not a recommendation for a specific commodity.
A stale probe aborts. Missing pre-cool confirmation aborts. Door open beyond the carrier's threshold after pre-cool complete and before the trailer is sealed aborts. Abort means the staging record is written as blocked, not that the trailer is secretly dispatched anyway.
Defrost is the false-alarm that will make dispatchers ignore the board if it is handled poorly. Return air rises during a normal defrost. A high-temperature abort that does not see a defrost flag will block healthy units on a schedule. The rule should suspend the high-temperature comparison for the defrost window reported by the unit, then require a post-defrost reading inside the freshness window before the stage can clear. A supply-versus-return spread that stays wide after a stable pre-cool, an illustrative example being more than about 8 F once the box should have settled, is a hold for a person, not an automatic clear. Calibration date on the probe asset belongs in the same hold path. The abort table is how the carrier writes those choices down so a later argument is about the rule, not about a screen someone remembers differently.
Suspend the high-temperature comparison for the defrost window reported by the unit, then require a post-defrost reading inside the freshness window before the stage can clear.
| Condition | Illustrative threshold | Board action |
|---|---|---|
| Stale probe | No sample inside 5 to 15 minutes | Abort. Do not reuse the last good value. |
| No pre-cool confirmation | Confirmation flag absent | Abort. Setpoint alone does not clear. |
| Door open after pre-cool | More than 10 to 15 cumulative minutes | Abort and require a new pre-cool confirmation. |
| Defrost in progress | Unit reports a defrost window | Suspend the high-temperature abort, then recheck. |
| GPS age only | Position older than the carrier window | Hold the lane comparison. Keep the temperature test. |
Writeback to a staging record a dispatcher accepts
The calculation does not update the live order. It writes a staging record that a dispatcher accepts. The record holds trailer identity, zone if any, order identity, commodity class, shipper setpoint, commanded setpoint, pre-cool start, pre-cool confirmed time, last probe value, probe time, unit, power status, GPS age, cumulative door-open seconds in the relevant state, and either a clear result or an abort reason. The dispatcher user id stays empty until a person accepts. Accept writes that user id and an accept timestamp. Reject writes a reason code and leaves the order untouched. Override writes the user id, the abort that was overridden, and a reason. No batch job is allowed to copy a clear stage into a dispatched status.
- Write the stage. The calculation writes a staging record, not the live order. The dispatcher user id stays empty.
- Accept. A person accepts, which writes that user id and an accept timestamp.
- Or reject. Reject writes a reason code and leaves the order untouched.
- Or override. Override writes the user id, the abort that was overridden, and a reason.
Writeback should be idempotent on the order and trailer pair plus the pre-cool cycle id. A repeated probe packet updates the same stage if the cycle has not been accepted, and it opens a new cycle if someone accepts and the box later fails a recheck. The dispatcher screen shows the stage beside the tender, including the age of the probe in seconds, so a green flag from twenty minutes ago cannot look current. If the telematics feed recovers after an abort, the stage flips back to blocked until the confirmation rules pass again. The point of the staging table is a single place where safety, operations, and a later FSMA record request read the same facts. It is not a second dispatch system.
A carrier can implement the staging record in the system of record it already runs, in a side table the dispatcher can see, or on paper if the volume is small, as long as the accept action has a name and a time. The predictive lead-time estimate is optional. Where history is thin, the honest design is the illustrative policy table replaced by the carrier's own numbers, plus the probe confirmation. The decision is whether the board can see the box before it accepts the load.
Counsel, shipper specs, and the limit of decision support
Shipper bills of lading, temperature protocols, and receiver rules govern the load. Some produce programs require a pulp check the carrier does not perform. Some protein programs require a continuous download at delivery. Some lanes require a specific recorder brand. This architecture does not absorb those documents into a score. It stores the shipper setpoint as an input and stops when the commanded setpoint disagrees. Counsel, not a dispatch screen, should confirm how the FDA Sanitary Transportation rule and the current 21 CFR text apply to a given contract, including who must train personnel and who must retain records. Strong Tower Consulting does not provide that legal conclusion on this page.
Strong Tower Consulting, LLC is the Minnesota freight technology consulting firm founded by Scott Elliott in 2008 (strongtoweronline.com). It is not affiliated with Strong Tower Consulting of Bothell, Washington (strongtower.consulting or strongtower.ai). The work described here is advisory. It does not operate a carrier's reefer units, speak to a shipper as the carrier, or guarantee that a pre-cool confirmation will satisfy a particular receiver. Decision support ends at the staging record. A person still dispatches the truck, the driver still runs the unit according to training and the shipper's instructions, and a temperature excursion in transit is handled by the carrier's existing escalation path.
Request an architecture review
A useful review starts from the carrier's real telematics payloads, a handful of recent pre-cool cycles, and the dispatch screen as it exists today. The questions are concrete. Can the board tell setpoint from box temperature? Is door state timed, or is it a latch that stays true through every delivery? Does anyone other than a shared login accept a temperature-controlled tender? Those questions can be answered from exports the carrier already owns. They do not require a pilot that moves live freight.
Strong Tower Consulting will walk through that evidence with operations and whoever owns the food-safety file, then leave a written gap list the carrier can implement in its own stack. Call 763-244-1373 or request an architecture review through the assessment form. The conversation is advisory. It does not create a shipper relationship, and it does not put an autonomous dispatcher on the board.
763-244-1373 | Request an assessment
Frequently asked questions
The questions below are the ones operations and food-safety leads usually ask when a temperature field is about to be added to a dispatch board. The answers restate the boundaries already drawn in the sections above. They are not a substitute for the shipper's protocol or for advice from counsel on the Sanitary Transportation rule.
Where a threshold appears in an answer, it is illustrative. The carrier's policy, the unit manufacturer's guidance, and the current 21 CFR text, confirmed with counsel, outrank any example on this page. A green flag on a screen is a staging aid. It is not a certificate that the freight stayed in range.
Is this page legal advice on the FDA Sanitary Transportation rule?
No. The FDA Sanitary Transportation of Human and Animal Food rule is the duty backdrop for shippers, loaders, carriers, and receivers. Confirm current 21 CFR requirements with counsel. This page is an architecture for decision support records, not a compliance opinion.
Does a confirmed setpoint mean the trailer is pre-cooled?
No. The setpoint is the temperature the unit is commanded to hold. Pre-cool is the measured pull-down of the empty box before loading. Pulp temperature is the product itself. A board that treats those three words as one field will accept a trailer that cannot protect the load.
Can the model dispatch the truck without a person?
No. The architecture writes a staging record. A dispatcher accepts or rejects that record. There is no path from a score to a dispatched status. This is decision support, not an autonomous reefer dispatcher.
What happens when the probe feed goes stale?
A stale probe aborts the stage. The board must not reuse the last good temperature as if it were current. The carrier sets the freshness window in policy. Any minute threshold on this page is illustrative.
Let the board see the box before it accepts the load.
Strong Tower Consulting provides independent systems architecture, feasibility audits, and engineering roadmaps for motor carriers and freight brokers. Contact our advisory team or call 763-244-1373 to discuss your operational data and evaluate practical implementation paths for your fleet.
Published October 23, 2026 by Strong Tower Consulting, LLC. Founded 2008 in Minnesota by Scott Elliott.