<P> Towboats in line - haul service operate 24 / 7 and have the latest in navigational equipment, such as color radar, GPS systems, electronic river charts, and specialized radio communications . </P> <P> Boats that traverse the Intracoastal Waterway (ICW) are commonly referred to as "ditch boats" or "canal boats". ICW tows usually consist of 1 to 4 barges ranging in size, usually "strung out" end to end when loaded or "breasted up" side by side when empty . </P> <P> Towboats always push the "tow" of barges, which are lashed together with steel cables usually 1 to 1.5 in (25.4 to 38.1 mm) in diameter . The term towboat arises from steamboat days, when steamboat fortunes began to decline and to survive steamboats began to "tow" wooden barges alongside to earn additional revenue . Eventually, the railroad expansion following the American Civil War ended the steamboat era . </P> <P> During the 19th century, towboats were used to push showboats, which lacked steam engines to free up space for a theater . </P>

How many barges are on the mississippi river