U.S. Intermodal volume growth was still chugging along in August, despite a slower-than-hoped-for recovery in both the country’s economy and train speeds.

U.S. intermodal traffic for the month of August was up 2.6 percent year-over-year, at roughly 9 million containers and trailers, according to the Association of American Railroads. August also saw intermodal volume growth hit a 10-week high early in the month and post its fastest weekly pace in roughly two months a week later. Intermodal traffic was up 5 percent year-over-year the week ending Aug. 22, at 278,972 units, the best growth American railroads had seen in eight weeks.

The intermodal industry continues to see healthy gains in volume, even if train speeds have not always matched. Train speeds, a barometer of overall service reliability, have been making year-over-year improvements, but are still down compared to speeds two years ago.

Moreover, those year-over-year gains are not a constant trend, said Larry Gross, a senior transportation analyst at FTR Associates. The railroads, he told JOC.com last month, are playing a game of give and take.

“They’ll see significant improvement in train speeds over the course of a week and then give it all back over the course of a holiday weekend,” he said.

On Aug. 26, average intermodal train speeds for the prior week had fallen back 0.2 miles per hour, erasing any gains the railroads had made earlier in the month, Gross posted on his Twitter account. The four-week average was up 2.8 percent year-over-year, but still down 5.5. percent compared to 2013 figures.

The first figures out in September “show no change,” Gross posted, for the week ending Aug. 28.

AAR Senior Vice President of Policy and Economics John Gray, however, said he was upbeat for the remainder of 2015.

“August had essentially the same rail traffic pattern as the previous few months: a healthy increase for intermodal, a big decline for coal, continued weakness in a variety of energy-related commodities, and strength in some other carload segments,” Gray said in a statement.

“Railroads are a derived-demand industry, meaning that demand for rail service is a function of demand downstream for the products railroads haul,” he said. “We’re optimistic that the economy will continue to grow. Demand for rail service should continue to grow with it.”

Read more here.