Tanker Vessel Dwell Times
The time vessels spend waiting in port is a major factor contributing to port performance. Vessel dwell times are the amount of time that vessels spend in port actively loading or unloading cargo, which in turn contributes to both port capacity and throughput performance. Shorter dwell times are usually desirable because vessel and marine terminal operating costs rise with dwell time.
According to the U.S. Energy Information Administration, in 2021 the United States exported about 8.63 million barrels of crude oil per day (b/d) and imported about 8.47 million b/d of petroleum, making the United States an annual total petroleum net exporter for the second year in a row. In turn, being a net exporter may have contributed to the decline tanker vessel traffic. The U.S. imports more crude oil that is low value than the refined products such a distillate fuel oil and propane/propylene exports, which are higher value. 
At these top ports,  average tanker vessel dwell times were estimated at 40.8 hours in 2021, down by about 36 minutes from 41.4 hours in 2020 as shown in the following figure. In general, tanker dwell times were taking about a third longer than container vessel dwell times, most likely because it takes more time to pump petroleum and crude oil than to lift shipping containers from a vessel of similar size. However, this difference in dwell times is narrowing as tanker vessel dwell times have decreased and containership dwell times have increased. 
Average tanker dwell times for individual ports are shown in the online Port Profiles.
 U.S. Department of Energy, Energy Information Administration, Imports/exports, available at https://www.eia.gov/ as of August 2022.
 The top tonnage ports are based on 2020 port rankings provided by the U.S. Army Corps of Engineer, Waterborne Commerce Statistics Center as of July 2022. The ports of Cincinnati-Northern KY; Huntington-Tristate, KY, OH, WV; Mid-Ohio Valley Port, OH and WV; St. Louis Metro Port, IL and MO are located on rivers and may handle primarily liquid bulk barges, which are not equipped with AIS and thus not included in the tanker dwell times.
 U.S. Department of Transportation, Bureau of Transportation Statistics, calculated using AIS data from the U.S. Coast Guard’s Nationwide Automatic Identification System (NAIS) archive, processed by U.S. Army Engineer Research and Development Center, Coastal and Hydraulics Laboratory, through the AIS Analysis Package (AISAP) software package as of October 2022. Numbers may not add to total due to independent rounding.