Rail & Road Connections

Nearly all major U.S. ports have National Highway System (NHS) connectors, which are the public roads leading to major marine terminals as well as the rail connection via on-dock or a nearby intermodal container transfer facilities (ICTFs). The NHS includes the Interstate and U.S. highways as well as other roads important to Nation’s economy, defense, and mobility. 
According to the Freight Analysis Framework, about 58 million tons (7.8 percent) of U.S. water imports were moved domestically by rail. Only about 13 million tons (22.2 percent) of the U.S. water imports were moved by rail less than 100 miles. About 2/3 of the tonnage moved 749 miles or less, more specifically about 34 million tons (58.3 percent), and a 1/3 moved of the tonnage moved 750 miles or more, more specifically about 24 million tons (41.7 percent). Many rail lines are configured to handle intermodal shipping containers, particularly double-stack trains.
For comparison, truck moved about 136,204 (41.8 percent) of the U.S. water imports less than 100 miles. Trucks primarily handle the short, local trips while rail handles more intermediate and long-distance, intercity trips. If a marine terminal does not have an on-dock rail connection, drayage trucks will ferry a steady stream of shipping containers to and from a nearby ICTF.  Trucks moved 299 million tons (91.8 percent) of their tonnage 749 miles or less, only 27 million (8.2 percent) were 750 miles or more. [1] The following figure shows the NHS connectors, which connect our Nation's ports to local markets, ICTFs, or the hinterlands.
Rail moves high-value, time-sensitive intermodal shipping containers (e.g., consumer electronics, appliances, etc.) as well as low-value breakbulk (e.g., forestry and steel products, etc.) or bulk commodities (e.g., coal, oil, etc.). A double-stack trains, consisting solely of double-stack container cars and locomotives, are optimized for moving intermodal shipping containers. Double-stack trains require greater tunnel clearances and specialized cargo handling equipment. However, double-stack train eases cargo un-/loading, and minimizes the overall footprint of the railyard.
Bulk terminals have a variety of rail service connections suited to the type and volume of commodities they handle. Rail provides an efficiency and effectively a low-cost way to move large amounts of freight cargo. Unit trains carry all the same, usually dry or liquid bulk commodities (e.g., coal, oil, etc.) and are shipped from the same origin to the same destination. The following figure shows the rail connection and facilities around many of the Nation's major ports.
Most container terminals have either on-dock transfer facilities within the marine terminal boundaries. On-dock rail eliminates the need for drayage trucks to ferry shipping containers to and from the marine terminal and ICTFs, helping reduce port congestion and improve efficiency. Other container terminals are located near off-dock facilities. The following figure shows the number of terminals by port with on-dock rail connections.
[1] U.S. Department of Transportation, Bureau of Transportation Statistics analysis of the Freight Analysis Framework (FAF5.3, base year 2017, July 2022), available at Freight Analysis Framework (FAF) (ornl.gov) as of August 2022.