The most fragile link in the cold chain is not the warehouse but the road. In the warehouse, temperature is stable, the door is controlled and an alarm is fitted; on the road, however, the vehicle waits under the sun, the door opens at every delivery, the unit is limited by fuel or battery, and the driver is alone. Refrigerated transport, under these conditions, means delivering the product at its departure temperature. To achieve this, the right body and unit are chosen, loading is carried out by measuring product temperature, stacking is arranged according to airflow, temperature is recorded continuously, and it is documented with a report at delivery. In the Aegean's summer heat, each of these is a separate planning matter.
The logic of the refrigerated body and cooling unit
A refrigerated vehicle consists of two parts: the insulated body and the cooling unit. The body is usually made from sandwich panels filled with polyurethane foam; its job is to slow the ingress of heat from outside. The quality of the insulation is measured by the K coefficient; the lower the coefficient, the less heat the wall transmits. Panel thickness, door seals, floor structure, and the moisture build-up that occurs in the foam with ageing determine this coefficient; the insulation of a ten-year-old body is not at its as-new value.
The cooling unit, meanwhile, cools and circulates the air inside the body. The most common misconception here is assuming the unit cools the product itself. The unit is sized to remove the heat leaking into the body and the hot air entering at each door opening; it does not have the capacity to bring a hot-loaded pallet down to target temperature, and when this is attempted, the evaporator ices up, airflow drops, and the product's outer surface freezes while its core stays lukewarm.
Three types are common, based on how the unit is driven. Units driven from the vehicle engine are found on light commercial vehicles; cooling stops when the engine is not running. Independent diesel-engine units are standard on heavy vehicles and trailers; they keep running even when the vehicle is stationary. The electric standby option lets the vehicle stay cold without burning fuel by connecting to mains power at the depot or loading bay; this feature is essential for vehicles waiting overnight.
The product temperature band is the decisive factor when choosing: a vehicle carrying only chilled goods (0 to +4 °C) needs different body insulation and unit capacity from one carrying goods frozen at -20 °C. A vehicle designed for frozen goods can also carry chilled goods; the reverse does not hold. The number and type of doors also matter: a side door on a distribution vehicle loses far less cold air than a rear door, which vents the whole body's air at every delivery.
The ATP Agreement and Vehicle Classes
ATP is the abbreviation for the Agreement on the International Carriage of Perishable Foodstuffs and on the Special Equipment to be Used for such Carriage. It was drawn up under the United Nations Economic Commission for Europe, and Türkiye is a signatory. It requires the insulation and cooling performance of refrigerated equipment used in international transport to be documented; many major buyers also require ATP-certified vehicles for domestic transport.
ATP classifies equipment by insulation and cooling method. Insulated but unrefrigerated bodies are divided into IN (normal insulation) and IR (reinforced insulation). Mechanically refrigerated bodies are known by the codes RRC (normal insulation, mechanical cooling) and FRC (reinforced insulation, mechanical cooling); the final letter indicates the temperature class. Class A equipment can maintain the body interior at any set point between 0 and +12 °C; class C, at any set point between +12 and -20 °C. In practice, vehicles marked FRC are sought for frozen food, and FRA or FNA for chilled food.
An ATP certificate shows that the vehicle has passed the body insulation test and the unit performance test; it is issued for a set period and must be renewed. An ATP plate showing the class code and expiry date is fitted to the outside of the body. When sourcing transport services, checking this plate and confirming the certificate is current is a far more meaningful check than simply judging whether the vehicle looks refrigerated from the outside.
Whether ATP certification is mandatory for domestic transport depends on the type of carriage and the buyer's requirements; but the insulation and cooling performance that ATP defines is the technical measure of whether a vehicle can do the job, certified or not. If in doubt, request written confirmation of the vehicle's insulation class and the interior temperature the unit can maintain at an ambient of +30 °C.
Pre-cooling and product temperature at loading
There are two types of pre-cooling before loading: of the body and of the product. Body pre-cooling means running the unit with the doors closed before docking at the ramp, so that the internal surfaces reach the target temperature. The walls of a body left standing in the sun can exceed 40°C; these walls transfer heat to the product. Standard practice is to bring the body down to the set point and run it for a few more minutes; however, the unit is never run with the doors open, because an open-door unit draws moisture from the outside air into the evaporator and causes icing.
Product pre-cooling means the product is already at the target temperature before loading. This is the warehouse's responsibility; the vehicle cannot make up for it. During loading, the core temperature of each batch is measured with a probe thermometer and recorded. Product outside the acceptable range is either sent back to the warehouse before loading, or loaded with the receiver's written approval together with a temperature note. If this step is skipped, the product can still arrive warm at delivery even though nothing went wrong en route — and it is the carrier who gets billed for it.
Dock time is managed just as closely. If there is no dock seal between the warehouse's cold door and the vehicle door, the product is exposed to outside air; in summer, even a five-minute wait produces a measurable temperature rise in leafy greens and frozen product. Pallets are not stockpiled in front of the door but loaded the moment they are ready; the loading list and paperwork are only completed after the vehicle door has been closed.
As soon as loading is finished, the door is closed immediately and the unit is started; before moving off, the driver checks the unit's set point and mode (continuous run or start-stop). Continuous run mode is preferred for sensitive and frozen products; start-stop saves fuel but causes temperature swings.
Stacking for airflow
Air inside the body is blown from the unit's evaporator along the ceiling towards the rear, drops down at the rear door, and returns along the floor to the front before heading back to the evaporator. If this cycle is broken, part of the body reaches the target temperature while the rest does not. Stacking rules exist to preserve this cycle.
An air channel is left between the ceiling and the load; in many bodies this height is marked on the interior surface and must never be exceeded. The load is not pushed up against the rear door; a gap is left at the back to let air descend. Where the floor has a T-bar or ducted profile, air already passes beneath the pallets; on a flat floor, pallets must be used. The product is not leant against the body walls; the walls are the main source of heat ingress, and a box resting against the wall is the first to warm up.
The area directly in front of the evaporator is always kept clear. A pallet placed right in front of or beneath the unit blocks the air return; the unit immediately draws back the cold air it has just blown out, reads the body temperature as lower than it actually is, and cuts out. This is one of the most common causes behind the complaint that the record shows the correct temperature, yet the product arrived warm.
Packaging affects airflow. Perforated boxes and stretch wrap left open around the pallet allow air to pass between products; a fully stretch-wrapped pallet, by contrast, only cools from the outer surface. For frozen product the situation is reversed: the product is already at its target temperature, a tight, compact stack preserves thermal mass, and it is enough for airflow to circulate only around the load.
Load distribution and securing matter just as much as temperature. A shifting pallet both crushes the product and blocks air corridors. Tensioning straps, dunnage bars and air bags are used; the corridor left between pallets is preserved through proper securing.
Multi-temperature (multi-temp) body
In distribution work, it is common for frozen, chilled and dry products to travel to the same customer together. For this, the body is divided into two or three sections with movable insulated bulkheads, each section has its own evaporator, and a single unit feeds these evaporators at different set points. Frozen product at -20 °C can be carried at the front, dairy products at +2 °C in the middle, and vegetables or dry goods at +12 °C at the back.
The advantage of a compartmentalised body is clear: one vehicle, one trip. The disadvantage is the added management burden. If a bulkhead leaks air or does not seat properly, the cold compartment cools the warm one, and the frozen compartment cannot hold its set point. Each compartment must have its own temperature record; a single-sensor record proves nothing on a three-compartment vehicle. Compartment capacity is not fixed; the movable bulkhead is adjusted to the amount of product, but at every adjustment care is taken over which compartment the evaporator ends up in.
Route planning determines how efficient a multi-temp vehicle is. Compartments are loaded to match delivery order: the product delivered last should sit furthest in, and the one delivered first should be closest to the door. Otherwise, pallets have to be repositioned at every delivery, the door stays open longer, and air mixes between compartments. Multi-temp bodies with side doors largely solve this problem.
For small fleet operators the investment cost of multi-temp is high; the alternative is to carry frozen product separately, in an insulated container or with dry ice. This works over short distances and in small quantities; on long routes and at high volumes, a compartmentalised body pulls ahead economically.
Data logger and temperature record at delivery
The unit's own display is not a temperature record; it measures return air and often does not log it. An independent data logger is placed inside the body at the level where the product sits, takes readings at set intervals and stores them in its memory. On long vehicles at least two points are measured, front and rear; in a multi-temp body each compartment is measured separately. The logging interval is chosen according to product risk; an interval of a few minutes is common practice.
Telematics-integrated systems relay temperature to the operations centre in real time via GSM and raise an alert if a threshold is exceeded. These systems allow intervention en route: the driver is called, the unit is controlled remotely, and the route is changed if necessary. In a vehicle without real-time monitoring, a deviation is only noticed on delivery — by which point there is nothing left to be done.
The delivery record is the closing document of the transport. In front of the recipient, the product's core temperature is measured with a probe thermometer, the data logger's printout or summary is attached, and the measurement time, the person who took it, and the product batch are recorded, with both parties signing. Product temperature and air temperature are kept on separate lines; the recipient mostly looks at the product temperature, while the record shows the air temperature — explaining the difference between the two is the carrier's job.
Rejection criteria are set out in writing in advance: for a given product, the product is rejected if a given temperature is exceeded for a set number of minutes. Without this criterion, every delivery turns into a negotiation. Records are archived digitally and kept accessible throughout the product's shelf life; being able to pull up the record of a trip from months earlier within minutes, when a customer complaint or an audit arises, is the carrier's strongest defence.
For consistency with the recording and alarm logic in the warehouse, you can take a look at our article on how a cold storage warehouse works; for the overall importance of the chain, see our article on why the cold chain matters.
Summer delivery planning in the Aegean
In Muğla and Aydın, midday temperatures in July and August climb close to 40°C; the body surface of a vehicle standing on asphalt rises well above that. If the unit is sized for a design condition of +30°C ambient, it runs at the limit of its capacity in this heat, and it takes longer to recover from the effect of each door opening. The summer plan is built on this reality.
The first principle is timing. Loading is done at night or in the early hours of the morning, and deliveries are aimed to be completed before midday. Deliveries left for the midday hours are sequenced so that door openings are kept to a minimum. In tourist districts such as Bodrum, Marmaris and Fethiye, summer traffic can double route times; planning is not based on winter timings.
The second principle is door management. At each delivery, only the pallet for that stop should be near the door, and the door-open time should be limited to minutes. Vehicles fitted with strip curtains can tolerate this; in a vehicle without curtains, body temperature rises rapidly the longer the door stays open. The driver confirms the recipient is ready to receive before opening the door; calling the recipient while the pallet waits at the door is the most costly mistake in the summer months.
The third principle is the vehicle's waiting condition. The vehicle is parked in shade or on a ramp and, where possible, connected to standby power. Driver breaks are scheduled by checking the unit's fuel status; especially for frozen cargo, it is confirmed before departure that the unit's fuel tank will last for the full journey.
The fourth principle is communication. The moment a route lengthens, traffic locks up, or a warning appears on the unit, the operations centre is notified; the delivery order is adjusted to prioritise the most sensitive product, or a temporary unload at a nearby cold store is arranged. In the Aegean, summer is also the period of peak food demand; volume increases are factored into the planned fleet size and trip frequency from the outset.
Common mistakes and working with the right partner
- Loading warm product onto the vehicle and expecting the unit to cool it down: the unit cannot cool the product; the product must leave the warehouse already at the target temperature.
- Skipping the pre-cooling of the box or running the unit with the door open: in the first case the walls warm the product, in the second the evaporator ices up.
- Placing a pallet in front of the evaporator: the record looks correct, but the product comes out warm.
- Loading right up to the ceiling: air cannot circulate through the back half.
- Carrying a multi-temp box with a single sensor: none of the compartments can be verified.
- Treating the unit's display as the record: the display shows return air and is not stored; an independent data logger is essential.
- Not keeping a delivery report: if a complaint follows, the carrier is left without any supporting document.
- Planning the summer route on winter timings: traffic and heat together extend the journey time, while the unit's capacity stays the same.
- Using start-stop mode for sensitive products: the fuel savings turn into temperature swings.
- Hiring a vehicle without checking the ATP plate: a "refrigerated" label does not tell you the insulation class.
What these mistakes have in common is that each looks minor on its own; but the cold chain is measured by its weakest link, not its total. When sourcing transport, ask in advance for the vehicle's class, the loading procedure, the recording method and a sample delivery report. As İTS Gıda & Lojistik, we apply these steps as standard procedure for food transport from Milas across the Aegean and beyond, managing cold storage and transport as a single chain; you can use our contact page to discuss your needs, or take a look at our facilities.
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