What is the difference between ETA and RTA?

The ETA is when the ship or truck expects to arrive; the RTA, requested time of arrival, is when the port or receiver wants it to. Just-in-time arrival works by sending the RTA early enough for the ETA to match it.

How accurate are vessel ETAs?

Often hours out. In a 2025 study, captain-provided ETAs were off by 22.15 hours on average against 16.01 for a model using satellite AIS — though captains did better in the last three days.

What makes an ETA reliable?

Live position, the route's real travel-time spread, and a stated location. Quoting the 80th-percentile time rather than the mean, as in the Dallas–San Antonio example, is what makes a promised time one you can keep.

Term

ETA (estimated time of arrival)

An ETA, estimated time of arrival, is the time a ship, truck or shipment is expected to reach a place — a port, a dock, a customer. Standards separate it from what is planned and what actually happened: the DCSA classes every event as estimated, planned or actual. A good ETA names where the arrival happens, not just when.

Also called estimated time of arrival, ETA in shipping, predictive ETA, RTA, requested time of arrival, ETDUpdated 13 October 2026

Estimated, requested, actual

Time	Who sets it	Example
Estimated (EST)	Whoever is moving — the ship, carrier or agent	The carrier's ETA at the dock
Requested / planned (PLN)	The receiving side — a port authority or terminal	The IMO's requested time of arrival at the pilot boarding place
Actual (ACT)	Recorded when it happens	The truck's gate-in

The IMO's just-in-time arrival guide says ships may spend 5% to 10% of their time waiting to get into port, and that a port telling ships their requested arrival time early lets them slow down instead of hurrying to wait. At Rotterdam, knowing it 12 hours ahead could have cut container ships' emissions in the port approach by 4% — 134,000 tonnes of CO2, in the IMO's figures. In a voyage simulation between Bremerhaven and Rotterdam, the ship burned 23% less fuel arriving just in time.

Worked example: a road ETA with a margin

Dallas → San Antonio, 2,622 truck trips: mean 4:38, 80th percentile 4:55 · leave 08:00 → mean ETA 12:38; promise 12:55 to be on time four times in five

Baseline travel times from the US DOT's I-35 FRATIS impact report, September 2018. The 17-minute gap between the mean and the 80th percentile is the buffer reliability costs.

How accurate are ETAs?

Not very, when typed by hand. A ship's AIS ETA is entered manually at the start of the voyage; a 2025 study using satellite AIS found a model's error lower than captain-provided ETAs overall (16.01 against 22.15 hours), though captains were more accurate in the final three days. For inland vessels into Rotterdam, a 2026 TU Delft study cut the mean absolute error by 79.55%, from 17.06 to 3.49 hours.

The mistake people make

Giving a time without a place. The IMO guide warns that an ETA that doesn't say whether it means the pilot boarding place or the berth can be several hours out in some ports. The same applies on land: an ETA to the city is not an ETA to the dock door.

FAQ