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.
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.