How the money works on this for folks who may not know
On voyage Charters:
A ship is fixed with a voyage commencement date/time and a cancel date/time. If the ship arrives prior to commencement, it is an 'arrived" ship but laytime ( the amount of time allowed for load/discharge in the charter) does not start until the commencement date/time. If the ship arrives after the cancel date - the charterer has ( with some conditions) the option to cancel the charter.
At the load port, if the ship arrivies inside the load window, and is delayed in berthing, the charterer of the vessel can claim against the supplier of the cargo for the cost of that delay. - this is called supply demurrage. Also, if ships arrive at the load port after the cancel date, the suppliers of the cargo can continue to bypass that ship in the berthing que - and berth ship that are inside their laycan in front of it - since they have no exposure for suppliers demurrage for ships that arrive outside the delivery window.
There is no speed required on the ballast passage to the load port. Although the ship is required to use “utmost dispatch” . On the laden passage vessel speed is negotiated and put in the charter party.
At the discharge port, the laytime clock starts when the vessel arrives. In general, the incentive is for the owner to get there and begin laytime. All delays in berthing are laytime. Charterers have delivery windows to meet with the recievers of the cargo and are need to meet those windows.
The point is the all the parites to the charter have different incentives and penalties on vessel timing. But the drive to save fuel and emmisions by minimising the delays in port is already happening - and gaining momentum. There is a whole budding industry in data management with this as a goal.
An aside - much of the speed management for timed arrival is a result of the new ability of slow speed diesels to steam at slower speeds. In my day, econ speed on my ships was about 12 kts. It usually make more sence for us to steam at 12 kts to the port, and then go on hotel bunkers- than to try a steam at slower speeds.