The wheels under your box, explained.

Ocean carriers in the US mostly stopped supplying chassis years ago. At NY / NJ, the wheels under nearly every box come from interchange pools — large leasing fleets (names you'll see include TRAC, DCLI, and FlexiVan) interchanged to motor carriers under the industry's UIIA agreement. The motor carrier outgates a chassis, uses it for the move, ingates it, and the pool bills per calendar day of use.

That daily billing is why chassis appears on your invoice as its own line: it is a metered cost that runs exactly as long as the move plus any storage-on-wheels does.

A chassis split happens when the box and the wheels aren't in the same place: the chassis must be picked up at, or returned to, a different facility than the container. That's an extra leg of driving, so it bills as an extra fee. Splits are sometimes forced (terminal chassis supply runs dry) and sometimes avoidable (planning the interchange around the move).

A flip is a lift event — moving a container from one chassis to another, usually because the first set of wheels failed inspection, was the wrong spec, or belongs somewhere else. Flips cost a lift fee and time.

Neither is exotic; both are managed. Dispatch that knows the day's pool supply at each start point books moves so the wheels are already where the box is.

Standard pool chassis carry standard weights. Overweight ocean containers need tri-axle chassis to run legally under New Jersey's overweight-container permit regime, and reefer moves may need gensets clipped to the chassis for road power. Specialty equipment is scarcer than standard wheels, so the profitable habit is booking it when the move is planned — not when the driver is at the gate.

A readable chassis line: days used, the daily rate, and any split or flip stated with a reason. Chassis days you didn't expect usually mean storage-on-wheels somebody didn't flag — which loops back to the free-time clocks and the value of a dispatch that watches them.