In maritime shipping, the term collision refers to ships that are in motion hitting each other, and the term allision refers to a moving ship striking a stationary ship or bridge.

A ship that strikes a bridge is said to allide with the bridge, experiencing an allision with the bridge.

This article reviews how modern shipping works to prevent ship strikes (allisions) of bridges.

---

Modern shipping uses much larger ships to transport goods, using less energy per ton than any other shipping method. It is the most efficient form of shipping cargo.

The larger ships are designed for open oceans, not inland waterways, and are being accomodated with larger ports built right on the oceans, usually on reclaimed land, so that the ships do not need to transit inland. From the ocean ports, smaller ships can transfer cargo to smaller inland ports.

In this new kind of shipping, the efficient larger ships can often avoid passing under bridges, since the modern ports for the larger ships are right on the oceans.

However, it is not always possible to avoid bridges. For example, to pass through the Suez Canal requires passing under a bridge.

---