Two years ago, U.S. shippers braced for a capacity crunch that would freeze freight at loading docks, unless shipments could be expedited with exorbitant amounts of cash. Trucking companies ordered trucks faster than factories could churn them out, as the U.S. economy finally shook off its post-recession lethargy and began to sprint toward higher ground.

That sprint ended in a stumble last year that left warehouses filled with stockpiled inventory and truckers wondering where all the loads had gone. The situation got worse for those truckers in early 2016. By the second quarter, truckload carriers were working hard to cut excess capacity, parking or selling spare trucks (in a soft used-truck market) and canceling truck orders.

In the first half of 2016, truck capacity was plentiful. The Council of Supply Chain Management Professionals in June pegged the number of excess Class 8 tractors at 80,000 units. “The demand imbalance has been very prevalent,” Jerry Moyes, founder and chairman of the largest U.S. truckload carrier, Swift Transportation, told Wall Street analysts in July.

That imbalance, however, is neither too deep nor systematic. A number of factors are likely to lead to a truckload capacity correction in the second half of 2016 and 2017 that would put more pressure on shipping rates. Shippers aware of the fragility of the demand imbalance already are voicing concerns with their trucking partners, according to carriers.

First, an excess of 80,000 tractors represents only 2.2 percent of the 3.6 million Class 8 trucks the American Trucking Associations says worked U.S. highways last year. How large of an increase in consumer or industrial demand would it take to absorb that layer of excess capacity?

Carriers aren’t waiting for demand to rise to bring supply-demand capacity more in line. Instead, they’re reducing supply. Swift operated on average 17,590 tractors in the second quarter, down 1.4 percent from a year earlier. The JOC Truckload Capacity Index dropped from 88.4 in the first quarter of 2016 to 87.6 in the second quarter, and was down from an eight-year peak of 90.4 in the third quarter of 2015.

There have been times already this year when excess capacity seemed to tighten quickly. “The difference between loose capacity and tight capacity seems like it’s closer than it’s ever been,” said Douglas R. Waggoner, chairman and CEO of Echo Global Logistics. “In the last two weeks (of June), with produce season and Roadcheck, capacity instantly went tight.”

And when it comes to capacity, truck numbers don’t tell the whole story. “Warehouses have only so many doors and ways they can handle” an influx of freight, said Walter Lynch, CEO and co-founder of Zipline Logistics. Increasingly, freight volumes are volatile and hard to forecast, and that’s making it more difficult to schedule, receive and load trucks, Lynch said.

The end-result is a reduction in real capacity, as delays eat up the time drivers can spend on the road, contributing to another capacity limiter, the driver shortage. Take all those factors into account, and a capacity correction may not be far away. Throw in an increase in consumer demand this fall, and it becomes more of a certainty. Shippers need to get ready. 

Contact William B. Cassidy at bill.cassidy@ihsmarkit.com and follow him on Twitter: @wbcassidy_joc.