From a network design perspective, for every weekly deep-sea liner service, one vessel would be scheduled to depart from an origin region each week. However, in the real world, a shipping line can have multiple vessels departing in the same week, on the same service. This can be caused by vessel delays, where a delayed vessel slides into the following week, vessel shortages where shipping lines deploy two smaller vessels to replace a larger vessel, or because of extra-loader vessels to cater to excess demand/cargo backlog. We term this phenomenon as “vessel bunching”, and it is defined as the number of sailings in a given week in excess of the number of weekly services, so if there are 17 sailings in one week, and there are 15 weekly services, “vessel bunching” equals 2. (....)