ARLINGTON, VA. — The American Trucking Associations’(ATA) advanced seasonally adjusted (SA) For-Hire Truck Tonnage Index was up a very slight 0.1 percent in June after May’s 2.1 percent increase.

Compared with June 2012, the SA index saw a healthy increase of 5.9 percent. That’s robust, ATA said, but still below May’s 6.5 percent year-over-year gain.

“The fact that tonnage didn’t fall back after the 2.1 percent surge in May is quite remarkable,” ATA Chief Economist Bob Costello commented. “While housing starts were down in June, tonnage was buoyed by other areas like auto production — which was very strong in June — and durable-goods output, which increased 0.5 percent during the month according to the Federal Reserve.”

Healthy auto sales helped push retail sales higher, also helping June’s tonnage level, Costello said. “The trend this year is heavy freight, like autos and energy production, is growing faster than lighter freight, which is pushing truck tonnage up.”

Year-to-date, compared with the same period in 2012, the tonnage index is up 4.7 percent.

The not seasonally adjusted index was 5 percent below the May’s level.