Correlation between coastal tides and the speed of commercial vessels

One way of saving fuel is to take advantage of the currents. This study investigates how the SOG of individual vessels in the Oslo Fjord is linked to current strength. The Oslo Fjord is approximately 150 km long; the areas of interest are one inner part and one outer part. The majority of vessels operating in these areas are heading either north (inbound) or south (outbound). Vessel traffic statistics for a duration of two years were collected by using the Automatic Identification System (AIS) and combined with tidal current measurements. Passenger, cargo and cruise vessels are considered. One finding is that the average SOG is in general larger for the vessels heading south than north in the narrow, inner parts of the Oslo Fjord. While in the wider, outer parts the average SOG is independent of the heading. The change in SOG due to tidal currents are stronger for passenger ferries heading south in the outer part of the Oslo Fjord even though the tidal currents in the outer part of the fjord are weaker than in the inner parts of the fjord. One simple explanation might be that the vessels adjust their speed through water to compensate for the currents in the inner parts of the fjord, but fail to readjust when the currents decrease in the outer parts of the fjord. The SOG of the cargo and cruise vessels seems to be less influenced by the tidal currents. The results indicate that several vessels can benefit more from exploiting the tidal currents to a larger extent.