Source: publicly reported data from each port.
What?: Monthly container trade volumes measured in twenty-foot-equivalent units (TEUs). Though most trade is conducted via forty-foot containers, TEU is the more common measure, though FEUs, which are just TEUs x2, would be closer to actual load volume.
Most loads require two drayage moves, with twenty-foot containers the main exception as they're more likely to remain in the port city, so TEU figures are a fairly good indicator of drayage demand.
Analysis: data sets are grouped by loaded/empty and import/export, with comparisons to the prior-year month, regional groupings, and seasonally-adjusted with special Chinese New Year seasonal factors.
Where?: There are a few other ports that can handle smaller container ships but do not report volumes, like Philadelphia, but the 13 ports included in this database represent at least 80%-90% of North American container trade.