Crane outreach and backreach: what they mean and why vessel size depends on them

Outreach and backreach are two numbers on an STS crane spec sheet that terminal planners and OEM sales teams argue about more than almost any other dimension. Get them wrong when matching a crane order to a berth's vessel calls, and you end up with a boom that can't reach the far side of an ultra-large containership, or a crane that swings into the apron equipment working behind it.

What outreach actually measures

Outreach is the horizontal distance from the waterside rail, the crane rail closest to the water, out to the farthest point the spreader can reach over the vessel. It's quoted in meters, measured from the rail rather than from the crane's centerline. A crane rated at 65 m outreach can get its spreader 65 m past that rail and no farther.

That number sets how many container rows across the ship the crane can actually pick up. A neo-Panamax vessel runs around 19 rows across. An ultra-large containership can run 24 rows or more. Each additional row pushes the required outreach out by roughly the width of a bay, plus margin for hatch coamings and lashing bridges in the way. A terminal quoting a crane at 51 m outreach is telling you, without saying so directly, that the crane was never built for anything past about a 13,000 TEU class vessel.

Backreach is the mirror image on the landside: the distance the boom and trolley can travel back over the landside rail, toward the apron. It matters less for vessel size and more for how the crane works with the equipment behind it, RTGs, straddle carriers, the chassis lanes. A crane with generous backreach can stack containers farther back on the apron before a hostler has to drive under the boom, which counts for something on narrow aprons where space behind the crane is already tight.

Why outreach drives the vessel size a berth can actually serve

A terminal can have a deep enough berth and a long enough quay and still turn away the largest ships calling on a string, because the cranes on that berth stop short of what the vessel needs. This is the mismatch port equipment OEMs watch for: a terminal operator who has committed to a service calling with 18,000+ TEU vessels, running an STS fleet ordered a decade earlier for a smaller class. That gap is where a crane order gets written. Knowing which terminals have it before the RFQ goes out is worth more than finding out after.

Air draft, the boom's height above the rail when raised for a vessel to pass under, and its height over the stack when lifting, does similar work alongside outreach. But outreach is the number that settles the width question outright. A crane can have all the air draft in the world and still be the wrong crane if the boom stops short of row 22.

Reading outreach off a crane you can't walk up to

Terminal operators don't publish outreach specs for every STS crane in the yard, and even when a maker's original data sheet exists, a terminal that bought secondhand or mixed its fleet over twenty years rarely has it on file anywhere public. What you can do without a site visit is read the boom geometry from a clear overhead image and work out roughly how far it extends past the waterside rail relative to the gauge of the crane rails. That gives a usable estimate of outreach class even when nobody at the terminal will return your call about the original purchase order.

That's the kind of read we build Crane Fleet Mapping around: a terminal-by-terminal inventory of STS and yard cranes with a height and reach estimate pulled from imagery, not from a vendor spec sheet nobody will send you.

If you're trying to work out which terminals in a market are stuck with outreach that can't serve the next vessel class, that inventory is the place to start, not the research project in itself.