Congestion at Durban rarely arrives as one clean announcement. It shows up as a vessel sitting at anchorage for two extra days, then a depot that only releases your container on the third trucking attempt, then a customer asking why the delivery date moved again. By the time the port authority publishes a notice, the delay is already baked into your week.
Where the delay actually starts
The berthing window is the first signal worth watching. When import volumes climb and terminal stacks fill up, carriers push the window out in small increments, and each shift pushes your cargo release, your trucking slot and your unpacking date with it. A berthing plan that slips by 36 hours is not a minor admin change; it usually costs you a full working day on the road side.
Trucking is the second bottleneck. During peak weeks, hauliers serving the Durban depots run short on slots because the same trucks are queued at the same gates. If you booked a collection for Tuesday morning and the depot is running a backlog, that slot disappears and the next realistic window may be Thursday. Plan the trucking after the release, not before.
Building an estimate you can defend
Quoting the carrier's best-case transit time to a customer is the fastest way to lose credibility. A more honest approach is to work backwards: take the vessel ETA, add a berthing buffer, add a release and documentation buffer, then add a trucking buffer. For Durban in a busy month, that combined buffer is often several days, not several hours.
It also helps to tell the customer what you are watching, not just the date. "Vessel is at anchorage, berthing expected within two days, release and trucking to follow" gives them something to plan around. A single moving date with no context does not.
Demurrage and detention exposure
When the port slows down, free time on the container starts running out faster than your release does. Demurrage accrues while the box sits at the terminal; detention starts once it leaves and you hold it longer than agreed. Both are avoidable costs if you track the free-time clock from the day the vessel berths, not the day you get the invoice.
The practical move is to keep the release documents ready before the vessel arrives, so the only variable left is the physical movement. If you handle your own paperwork, the SAD 500 and clearance notes are worth reading alongside this, because a stuck declaration makes congestion worse.
What to do this week
Check the berthing schedule before you commit a trucking slot. Confirm depot opening hours and queue behaviour for the specific terminal you are using. Keep a written buffer in your delivery estimate and share it with the customer early. And if you are still deciding how to move the volume, groupage versus a full container changes how much congestion risk you carry.