A Glimpse into Vessel Dwell Times
Vessel dwell time is a hot button for the container shipping industry. Besides the cost involved on both the land side and the water side, there are serious concerns about the ability of terminals to handle new megaships promptly and efficiently.
The Automatic Identification System (AIS) transmits precise vessel location data and speed data, giving operators, government agencies, and industry analysts far better and more complete information on vessel movements and dwell times than ever before. In the U.S., AIS data are compiled by the Coast Guard in the Nationwide Automatic Identification System and its database. Industry researchers and academics are just beginning to work with AIS data, and there is much to be learned about AIS strengths, limitations, and interpretations.
A preliminary look at the AIS data for major U.S. container ports shows that dwell times are highly variable, with vessels of the same size and even multiple calls of the same vessel having very different dwell times on different dates.
Moreover, there is only a very loose relationship between vessel capacity in TEU and dwell time. Larger vessels are often handled in less time than smaller ones.
Initial analysis indicates that vessel dwell time is driven by schedule and cargo volume, not vessel size. There appears to be a close relationship between the average number of containers handled per call and the average vessel dwell time across all major U.S. ports. Moreover, vessels that arrive within their expected schedule window seem to have fairly consistent dwell times. Vessels that arrive early tend to have longer dwells, suggesting that they have to wait for terminals’ resources even after they berth. Vessel that arrive late tend to have shorter dwell times, suggesting that terminals put on extra resources to turn them on schedule.
Overall, this early glimpse into vessel dwell time data fits with a rational pattern of vessel and terminal planning and scheduling, with cranes and labor allocated to achieve the required throughput during the scheduled call. Terminals that can deploy the required resources can unload and load megaships on schedule. The strains might come if megaships are used to condense multiple services, requiring the terminals to handle more containers during the same scheduled call.
Dan Smith is a Principal with The Tioga Group: www.tiogagroup.com