Domestic intermodal volumes hit a new annual high of 21,697 loaded containers on Sunday, Sept. 28, according to FreightWaves data, and volumes stayed elevated into the final day of the third quarter. The 7-day moving average marks the strongest reading of the year for the segment and confirms that freight keeps shifting from over-the-road to rail on historically wide cost advantages.

The record layers seasonal tailwinds onto an already strong baseline. Domestic container volumes normally climb from August into September, but this year that lift is running on top of roughly 8% year-over-year growth — a combination Julie Van de Kamp flagged as significant.

"That combination of the two is really kind of worth noting and continuing to watch," said Van de Kamp.

Savings still the engine of conversion

Cost remains the primary driver of mode conversion. FreightWaves' Intermodal Contract Savings Index has eased from a peak of more than 33% in mid-August to approximately 30.9% as of Wednesday, but Van de Kamp called that level "really historically high."

Lane-level opportunities are stark. The Harrisburg-to-Atlanta corridor shows savings of 43% against current elevated spot truck rates, while outbound California lanes into Ohio offer more than 42% savings. For shippers moving freight on those corridors, the economics continue to favor intermodal by a wide margin despite softer rail service over the past year.

Rail service has slowed somewhat as more freight has moved to the rails, but the deterioration has not been enough to deter shippers given the magnitude of the savings on offer.

Q4 capacity squeeze and rate risk

Capacity pressure is building. Van de Kamp noted that each additional week of volume growth will tighten available intermodal capacity, strengthening the case for a rate increase in the fourth quarter. Shippers and forwarders who have enjoyed double-digit savings may find carriers pressing for higher contract rates as boxes and slots fill.

The forward view supports continued growth. FreightWaves' seasonally adjusted moving average — a forecast anchored to current trend and historical seasonality — suggests loaded domestic intermodal volumes could grow by another 4% heading into Thanksgiving. Van de Kamp cautioned the projection does not account for economic factors and could shift if demand weakens, service deteriorates, or intermodal rates rise significantly.

International intermodal cools after early pull-forward

International intermodal container volumes tell a different story. The FreightWaves index holds steady at 13,620 containers, down from a high of around 15,000 in July. Van de Kamp attributed the moderation to importers pulling shipments forward earlier in the year, producing a more elongated but somewhat muted peak season rather than a sharp late-summer surge.

The pattern mirrors what over-the-road volumes showed during the same period, suggesting the front-loaded import wave — not a demand collapse — explains the international intermodal softness.

For domestic shippers, the message heading into Q4 is straightforward: the conversion economics remain compelling at roughly 31% savings, but capacity is tightening by the week, and intermodal carriers now have a credible case for raising rates as Thanksgiving volumes build.