Rolling cargoes on and off a floating vessel usually entails a trailer negotiating a temporary linkspan that bridges between the quay and the floating vessel.
When rolling cargoes on and off a vessel, it is important to ensure that the trailer operator and the ballasting team are in close contact and controlled by a single person who has overall control of the operation. It is their job to ensure that the tide (if any) is monitored, the rate of change of the vessels draught and trim matches the ballast plan, and any risk of a cut in the tide is planned for and understood. A cut in a tide is where a tide does not make the predicted level due to weather or other seasonal issues.
The positioning and design of the linkspan can often assist with increasing the capacity of an operation and allow for a greater range of tides to be employed or increase the safety margin against a tide cut.
As very high loads are placed on each end (one end will see the load from the cargo coming aboard and the other end will see the weight of ballast countering this) the longitudinal strength of the vessel must be considered. Barges have been known to break in two as large loads come on board if these large bending forces are not considered.