U.S. freight-rail traffic rose in Week 37, Progressive Railroading reported this week, registering a positive weekly reading as autumn grain movement and intermodal restocking accelerated through mid-September.

Week 37 of the calendar year falls inside the post-Labor Day window in which carloads of grain and grain products begin advancing south from upper Midwest origins, retailers rebuild inventory in advance of late-November promotional activity, and utility coal demand begins tapering as summer air-conditioning load recedes.

What is the Week 37 reading based on?

Progressive Railroading circulates the headline increase in its weekly notification sent to railroad career professionals. The trade publication aggregates Association of American Railroads (AAR) data, which compile weekly submissions from the seven Class I railroads operating in the United States — BNSF, Union Pacific, CSX, Norfolk Southern, Canadian National, Canadian Pacific Kansas City and Ferromex, which retains Class I status through Kansas City Southern's Mexico gateway.

The AAR weekly comparison is constructed year over year, removing the holiday-and-weather distortions that often affect raw month-over-month readings. The dataset splits traffic into two principal categories. Carloads cover single-commodity shipments including coal, grain, chemicals, automobiles, metals and forest products. Intermodal units combine truck and rail for container and trailer movements. Each category is further subdivided by commodity group, allowing analysts to identify the segment driving any week-to-week change.

Cumulative and rolling comparisons smooth out week-to-week volatility. Year-to-date trends track cumulative volumes from January through the current reporting date. Trailing-13-week and trailing-52-week aggregates filter out single-week anomalies and reveal whether the network is gaining or losing modal share against long-haul trucking.

Why is the mid-September timing significant?

Mid-September traffic typically captures two seasonal forces working in different directions. Grain carloads begin climbing toward the harvest peak in early October, especially across the corn belt, while utility coal load eases as air-conditioning demand tapers with cooler nights. Intermodal units usually lift as retailers rebuild inventory for autumn promotional cycles, while automotive volumes respond to model-year changeovers scheduled at this time of year.

The net effect on the headline total depends on which segment carries the most weight that week and on the prior-year base. Comparisons against weaker 2024 readings in selected weeks can flatter the year-over-year move, while stronger 2024 weeks can mask genuine improvement. Weather disruptions — Gulf hurricanes that interrupt chemical shipments and intermodal flows, or Pacific Northwest precipitation that affects grain export windows — introduce additional variability.

For shippers and investors watching the data, weekly readings carry limited weight individually but accumulate into clear signals over multi-week spans. A run of three or four consecutive positive year-over-year comparisons tends to support rail-carrier earnings momentum in the next quarterly report.

What happens next across the network?

The grain corridor will be the most demanding test of network capacity through October. Weekly crop-progress reports from the U.S. Department of Agriculture set the pace for car orders across Iowa, Illinois, Nebraska and the Dakotas, the four states that typically anchor the harvest-to-export pipeline. BNSF and Union Pacific, which dominate the western and southern grain corridors respectively, watch these reports closely to plan locomotive distribution and crew availability.

Coal demand will track weather and gas-price dynamics through the heating season. Any early cold snap in the Midwest or Northeast would pull additional unit-train starts out of the Powder River Basin and Illinois Basin origins, two of the largest coal-shipping regions in North America. CSX and Norfolk Southern, with significant eastern utility-coal franchises, would see the largest direct impact.

Intermodal performance hinges on inventory positioning before the peak holiday shipping window. Earnings calls from major retailers and consumer-goods shippers in mid-October typically disclose stock-to-sales ratios that telegraph whether restocking will accelerate into the fourth quarter. Sustained widening of the truck-to-rail cost advantage of the type observed through much of 2024 would pull additional long-haul intermodal freight to the Class I network, lifting volumes without requiring additional locomotives or crews in the near term.

The Week 37 reading adds one data point to an uneven recovery. Whether the autumn peak holds across grain, coal and intermodal will determine if full-year U.S. freight volumes close with a clear rebound or a more modest gain compared with 2024.