Dwell Time

Dwell time is the length of time a shipping container stays at a marine terminal, rail yard or depot between arriving and leaving. For an import, it usually runs from the moment the box is discharged from the ship to the moment it leaves the gate on a truck or train; for an export, from gate-in to loading on the vessel. Terminal operators, port authorities, ocean carriers and cargo owners all track it because it shows how smoothly cargo is flowing.

Container dwell time is different from vessel port time, which measures how long the ship itself spends in port, although the two often rise together. Dwell time is closely tied to demurrage, the charge for leaving a box at the terminal beyond its free time, and to detention, the charge for keeping a carrier's box outside the terminal too long.

Think of an airport baggage carousel. Most bags are collected within minutes, but a few circle for an hour because their owners are stuck at passport control or have gone to the wrong hall. If too many bags are left on the belt, new ones have nowhere to drop, and the whole system slows.

A container terminal works the same way. Each box is meant to be picked up and taken away soon after it comes off the ship. When boxes sit for days, the stacks grow, cranes and trucks have less room to work, and the next ship has to wait. Dwell time is simply a count of how long the boxes are left on the belt.

Ports usually report average dwell time in days, split by type of move:

• Import dwell. Time from discharge to gate-out, often reported separately for boxes leaving by truck and by on-dock rail.
• Export dwell. Time from a loaded box entering the terminal to its loading on a ship.
• Empty dwell. Time an empty container waits before being returned to a carrier or repositioned.

Averages can hide long tails, so operators also count the number or share of boxes that have dwelt longer than a threshold, such as five or nine days. The cost to the cargo owner of a long import dwell can be estimated as:

• $C$ is the demurrage charge, which applies only when $D \gt F$.
• $r$ is the daily demurrage rate.
• $D$ is the number of days the box dwelt at the terminal.
• $F$ is the number of free days allowed.

If a terminal allows four free days and an import box sits for nine days at $150 a day, the charge is $150 \times (9 - 4) = 750$, or $750. Real tariffs often rise in tiers the longer a box stays, so the formula gives a lower bound.

Dwell time lengthens when any link after the ship is slow. Common causes include customs or health inspections, unpaid duties, late release of the bill of lading or other documents, shortages of trucks, drivers or chassis, full warehouses that cannot receive cargo, and rail congestion inland. Empty boxes also add to dwell when carriers delay empty container repositioning. Practices such as the street turn, extended gate hours and appointment systems are used to cut it, and freight forwarders often book trucks before a ship arrives so boxes leave quickly.

Dwell time became front-page news during the pandemic shipping crisis, when a surge in US imports met labour shortages and full warehouses. At the Port of Los Angeles, the executive director reported container dwell at a peak of about 11 days in autumn 2021, against typical pre-pandemic levels of under four days for local deliveries. In October 2021 the ports of Los Angeles and Long Beach approved a temporary "container excess dwell fee" on ocean carriers of $100 per container per day, rising by $100 each day, for truck-bound imports that stayed nine days or more. The fee was postponed repeatedly as backlogs eased, never collected, and ended in January 2023. The episode fed the freight-rate spike tracked by measures such as the Global Supply Chain Stress Index and added to goods inflation. It also raised costs for container leasing customers, whose per diem kept running while boxes sat idle.

Dwell time itself is not regulated, but the charges it triggers are. In the United States, the Federal Maritime Commission (FMC) published an interpretive rule on 18 May 2020 saying that demurrage and detention should be judged by whether they actually encourage cargo to move. The Ocean Shipping Reform Act of 2022, signed on 16 June 2022, directed the FMC to go further. Its final billing rule, issued on 26 February 2024 and effective from 28 May 2024, limits who may be billed, sets minimum invoice contents and requires invoices within 30 days of the last charge; a billed party need not pay an invoice that breaks these rules. Other countries handle the issue through port tariffs, competition law or contract terms, and international sales contracts allocate the risk using Incoterms. Because TEU throughput depends on yard space, dwell time remains one of the main measures of a terminal's capacity in international trade, particularly on the busy headhaul import leg.

• Federal Maritime Commission
• Port of Los Angeles