Dunnage Bag Levels
The difference between the over-the-road type and Level 1, 2, 4 and 5: which level applies to which transport mode and void type — a comparison guide based on the AAR Closed Car Loading Guide.
| Over-the-Road Type | Level 1 | Level 2 | Level 4 | Level 5 | |
|---|---|---|---|---|---|
| Transport Mode | Road only (truck/trailer), no transfer | Intermodal (container; ship + rail + truck transfer) | Intermodal (container; ship + rail + truck transfer) | Heavy rail (closed rail car / boxcar) | The heaviest rail loading scenarios |
| Void Type | General-purpose void filling | Lateral void — at the sides of the load | Longitudinal void — at the front/rear of the load | Large-volume voids inside the rail car | Voids specific to special load shapes, such as paper rolls |
| Typical Load Example | Palletized general cargo, domestic shipments | Palletized/boxed container cargo | Automotive parts, white goods, machinery | Heavy industrial goods, metal coils/reels | Paper pulp rolls, very heavy rail shipments |
| Transfer / Handling Exposure | None — single transport mode | Medium-high — multi-mode transfer | Medium-high — multi-mode transfer | Low — single mode, but high dynamic load | Low — single mode, highest dynamic load |
Why Level Matters
When buying a container dunnage bag, the "level" isn't just a product variant — it's a classification that determines which transport mode and which void type your load can safely use it for. Using a level that doesn't match the transport mode can result in inadequate load securing, and some intermodal and rail operators may require evidence that a specific level has been met before approving a load. Knowing the right level is therefore not just a product choice — it's a decision that can affect whether a shipment gets accepted at all.
What Is the AAR Closed Car Loading Guide?
Dunnage bag levels are defined in the Closed Car Loading Guide, published by the Association of American Railroads (AAR), the body representing the North American rail industry. The guide was originally developed for closed rail car (boxcar) loading, but has since become a widely used reference in intermodal container shipping as well. Its classification is based on which void type and which transport mode a dunnage bag is intended for, rather than on a kilogram figure for how much load it can bear.
Comparing the Levels
The table below summarizes which transport mode and void type each level is designed for:
Over-the-Road Type (Sometimes Labeled "Level 0")
Over-the-road dunnage bags are designed for shipments made solely by truck, with no container or rail-car transfer involved. Some supplier catalogs number this type as "Level 0," but this label isn't a standard term within the AAR guide itself — the term "over-the-road" is closer to the guide's original terminology. Because there's no transfer involved, this type is exposed to less dynamic load than the other levels.
Level 1: Intermodal for Lateral Voids
Level 1 is designed to fill the voids that form at the sides (left and right) of a load in intermodal container shipping. In this mode of transport, the load is transferred multiple times between sea, rail and road; each transfer is an additional point where dynamic force can push the load sideways. This is the level most commonly encountered with palletized or boxed general cargo.
Level 2: Intermodal for Longitudinal Voids
Level 2 is also used in intermodal shipping, but targets a different void direction: the longitudinal voids that form at the front or rear of a load (toward the container door or the front wall). Longitudinal voids typically occur when a container can't be fully loaded and the cargo doesn't span the container's full length; if left unfilled, this void lets the load shift forward and backward during braking and acceleration.
Level 4 and Level 5: Heavy Rail Loading
Level 4 and Level 5 are defined for closed rail car (boxcar) loading, the guide's original area of application, and cover the scenarios that demand the highest durability. Level 5 in particular is a dedicated class for securing cylindrical, heavy loads such as paper rolls inside a rail car — these loads create a different contact geometry and higher point loading than flat, palletized cargo.
Why Intermodal Transfer Adds Extra Risk
In an over-the-road shipment, the load is loaded onto a single vehicle and stays on that vehicle until it reaches its destination. In an intermodal shipment, the same container is lifted, jolted, and sometimes subjected to sudden stops multiple times as it moves from ship to quay, and from quay to rail or truck. Every transfer point is a moment when the voids inside the container are effectively retested — even if a void was adequately filled at the previous stage, the differently-directed acceleration during transfer (particularly the sudden pull-push motion seen in rail shunting) can cause the load to move in an unexpected direction. What sets Level 1 and Level 2 apart from the over-the-road type is that they're designed to withstand this repeated, multi-directional dynamic load.
How Level Information Appears on Product Packaging
If a dunnage bag supplier markets its product against a specific level, that information is expected to be stated clearly on the product packaging or in the accompanying technical documentation. For a product with no certification claim, the absence of a stated level can mean the product is manufactured for general-purpose, over-the-road use and doesn't carry intermodal or rail certification. Before shipping, it's advisable to confirm in writing, in the supplier's documentation, which level the dunnage bag has been tested for.
Why "Level 3" Varies by Source
Some supplier catalogs list a "Level 3" positioned between Level 1 and Level 4; however, this intermediate class isn't defined separately or consistently in the widely referenced classification of the AAR Closed Car Loading Guide. This inconsistency stems from different suppliers in the dunnage bag industry interpreting the guide according to their own product ranges. If you come across a product labeled "Level 3," we recommend confirming directly with the supplier which void type and transport mode it has been tested for — the label alone doesn't provide enough information.
Why Kilogram Figures Don't Appear on This Page
Some sources online publish a fixed kilogram-based lateral force rating for each level. These figures don't come from the AAR Closed Car Loading Guide itself but from supplier marketing materials, and they're inconsistent across sources — different suppliers state different kilogram values for the same level. For that reason, this guide describes the levels according to the guide's actual basis — void type and transport mode — rather than a force rating; the actual strength rating of a specific product should be confirmed from that product's own test certificate or the supplier's technical documentation.
How Do You Choose the Right Level?
- Transport mode: Is the shipment road-only, or does it involve intermodal or rail transfer?
- Void direction: Is the void at the sides of the load (lateral), or at the front/rear (longitudinal)?
- Load weight and rigidity: Heavy, rigid loads generally require a higher level.
- Buyer/carrier requirements: Some intermodal operators or buyers may request documentation confirming that a specific level has been met — confirm this requirement before shipping.
Consequences of Choosing the Wrong Level
Using a level that doesn't match the transport mode results, at best, in the load shifting and being damaged in transit. In more serious cases, an intermodal or rail operator may find the loading non-compliant with standards and reject the shipment or demand repacking — leading to both extra cost and unpredictable delivery delays.
Use Alongside Other Cargo-Securing Products
A dunnage bag fills the voids inside a container to limit the load's horizontal movement; but the integrity of the pallets themselves is maintained with strapping, and slippage underneath a pallet is prevented with anti-slip rubber pads. A comprehensive cargo-securing strategy generally requires using all three of these products together — a dunnage bag on its own isn't the whole loading plan, but one part of it.
The Relationship Between Level and Material Type
Level refers to which void type and transport mode a dunnage bag is designed for; material (kraft or PP woven) refers to which raw material the body is made from. The two properties are independent of each other — both a kraft and a PP woven version can be produced for the same level. On long, humid routes, the durability of a PP woven body may be the preferred choice, while level selection continues to be made independently of that choice, based on transport mode and void type.
Frequently Asked Questions
- What is "Level 0"? It's a label used in some catalogs for the over-the-road type of dunnage bag; it has no official equivalent in the AAR guide.
- Can more than one level be used in a single container? Yes — different levels can be used together within the same container for different void types; what matters is that each void is filled with the level appropriate to its type.
- What level are Pakkora's dunnage bags? This information will appear in the technical specifications table on the container dunnage bag product page; the field is left blank until it can be confirmed with supplier data.
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