Guides
Port congestion, explained
How the numbers on this site work: the three distinct dwell metrics kept apart, what a TEU is, how demurrage and free time work, and how the import-friction read is built. Each guide is built on the same live data as the board, so the examples are real and current.
Reading the metrics
Dwell, explained precisely: vessel dwell vs box dwell vs ships waiting
Container dwell time means three different things at a port, and treating them as one number is how readers reach the wrong conclusion. Vessel dwell is how long a ship sits at a berth, box dwell is how long an import container sits on the terminal, and ships waiting is a count of vessels queued offshore before a berth opens. Only the ship queue is a live weekly figure; the vessel-dwell series is archived and box dwell lags about two months.
From ship to your warehouse: the import chain
An import container moves through a fixed sequence: it arrives on a ship, is discharged at the terminal, sits in the yard, leaves by truck or rail, and reaches a distribution center. Each public congestion metric sits at one point on that chain, and the costly delays cluster on land, in the yard and at the gate, not at sea.
Volumes and demand
What is a TEU?
A TEU is a twenty-foot equivalent unit, the standard way ports count container volume. One twenty-foot box is 1 TEU and one forty-foot box is 2 TEU, so a port's monthly TEU total mixes both sizes into one comparable number. The monthly statistics split that volume into loaded imports, loaded exports and empties.
Why LA/Long Beach dominates, and when freight shifts east
LA/Long Beach is the largest container gateway in the US because it is the closest major port complex to Asia's factories, where most US containerized imports originate. Freight shifts toward East and Gulf Coast ports when West Coast labor risk, canal economics or the rate gap between routes tips the math, and those shifts show up slowly in the volume data.
Peak season: why imports surge August to October
Peak season is the late-summer-into-fall stretch when US container imports run highest, historically August through October. Retailers front-load holiday inventory so it clears the ports and reaches shelves before the fourth quarter, and the factory calendar on the other end shapes the annual rhythm. In recent years the peak has drifted earlier.
Reading the monthly TEU release
A port's monthly TEU release is its official count of the containers it handled, published a few weeks after the month closes. Read it three ways: against the prior month, against the same month a year ago, and against the pre-pandemic 2019 baseline. Loaded imports are the demand signal and empties are the repositioning tell.
What moves ocean freight rates
Ocean freight rates move on three forces: how much vessel capacity carriers offer, how much cargo demand is chasing it, and whatever disruption is reshaping the routes. This site does not track ocean spot rates and carries no rate feed. It reports container volumes and port congestion, which are context around rates, not the rates themselves.
Fees and the clock
Demurrage, detention and free time
Demurrage and detention are two different late fees on a container. Demurrage is what the terminal charges when your import box sits in its yard past the free time. Detention is what the carrier charges when you keep its container too long after you take it away. The last free day is the deadline before demurrage starts to accrue.
The clocks an importer watches
An import container passes a fixed set of milestones, and each one starts or stops a clock the importer cares about: estimated arrival, berth, discharge, available for pickup, the last free day and outgate. Knowing which public congestion metric lights up which clock turns a tracking screen into a plan.