How to load a trailer: pallet patterns and sizes

The trailers food distributors run most, how many pallets fit each way, and how to load a reefer so the cold reaches every pallet.

This guide covers the trailers a food distributor uses most, how many standard 48 by 40 inch pallets fit in each, the patterns you can load them in, and a step-by-step for loading a reefer the way the USDA handbook says to.

The common sizes

Outside, almost every US van and reefer is 102 inches wide. Inside is what counts, and it varies by maker, year and wall type. Wabash lists 101 inches wall to wall for its current DuraPlate dry van, with about 110 inches of height. Reefers have thick insulated walls, so dealer listings for 53-foot reefers usually show about 98 inches inside. Measure your own trailers before you plan a pattern.

• 53-foot van or reefer. The workhorse. About 26 pallets on the floor loaded straight.
• 48-foot van or reefer. Common in older and regional fleets. About 22 pallets straight by the same math.
• 28-foot pup. Run in pairs or alone for tight city stops. About 12 pallets straight.
• 24 to 26-foot box truck. No CDL needed at 26,000 pounds gross. Rental fleets list up to about 10,000 pounds of payload and 1,500 to 1,800 cubic feet.

The load patterns

Straight, turned and pinwheel

A 48 by 40 pallet can face two ways. Straight means the 48-inch side runs down the trailer, so two pallets side by side take 80 inches of width. That fits any trailer and leaves room to work. Turned means the 40-inch side runs down the trailer, so two across take 96 inches. Each row is shorter, so more rows fit: on paper, 15 rows and 30 pallets in a 53-footer instead of 26. The catch is width. 96 inches fits a 101-inch van with little room to spare and barely fits a 98-inch reefer. Pinwheel turns every other pallet, with the two lanes out of step, so a turned pallet always sits beside a straight one. That needs only 88 inches across and, by the same math, fits about 28.

Patterns for reefers

In a reefer, the pattern has a second job: let cold air reach every pallet. The USDA handbook on moving perishables by truck, updated by the University of Florida in 2019, names five patterns for top-air trailers: airflow, center-loaded, wall-loaded, offset and pinwheel. It prefers center-loaded (pallets in the middle, gaps at both walls, held with spacer blocks) and airflow (a gap down the middle). It does not recommend pinwheel, and says pinwheel pallets must be 4-way or air cannot pass under the load.

Keeping the load off the walls matters more than it looks. The handbook's example shows center-loading leaves no cartons touching the walls or floor, against about 15% when pallets sit against the walls. The air gap works as insulation.

How cold air moves

In a top-air reefer the unit blows cold air out along the ceiling, often through a chute. It comes down at the doors and returns along the floor to the front. So the rules follow the air:

• Leave space above the load and never block the chute or the unit.
• Leave at least 4 inches between the load and the rear doors.
• Use pallets when the floor channels are shallower than 2¼ inches.
• Never wrap film down to the floor; it blocks the return air.

Weight, front to back

On the Interstate a rig is capped at 80,000 pounds, with 34,000 pounds on each tandem. A five-axle truck only reaches 80,000 if the load is spread so neither the drive tandem nor the trailer tandem goes over. Drivers slide the trailer tandem to move weight between them. Heavy pallets go on the bottom, and toward the front, but not all at the nose.

Step by step: loading a reefer

1. Inspect. Door seals tight, no torn walls or insulation, floor channels and drains clear, return-air bulkhead open.
2. Check the set point. It should match the product.
3. Pre-cool the trailer. To set point at a cold dock. At an open dock, about 5°F above set point if loading takes 15 to 20 minutes, less if it is slow. Turn the unit off while the doors are open, or the coil ices.
4. Load cold product only. A reefer holds temperature; it does not pull warm product down. Note any warm pallets on the paperwork.
5. Load in reverse stop order. Last stop at the nose, first stop at the doors.
6. Use the pattern. Center-loaded or airflow, gaps at the top and the doors.
7. Secure it. Load bars, airbags, bracing or strapping on any gap. Pallets tight against each other and the walls can meet the federal rule on their own.
8. Seal and record. Write down the seal number and the temperature.

Dock to Route builds each load against floor spots, cube, weight and temperature, and prints the nose-to-doors order for the dock crew.

Sources

• USDA Agricultural Handbook 669, protecting perishable foods during transport by truck
• UF/IFAS HS1328 (2019 update of AH 669)
• Thermo King, air management
• Wabash, DuraPlate dry van spec sheet
• Hale Trailer, pallets on a 53-foot floor
• Penske, 22 to 26-foot box truck
• FHWA, federal weight limits and 49 CFR 393.102