ARLINGTON, Va. — US for-hire truck tonnage jumped 2.3%, reaching the highest level on record, according to the latest figures from the American Trucking Associations.

May’s gains came on the heels of a 0.2% decline in April.

May’s seasonally-adjusted tonnage is the highest reading since December 2011. Compared to May 2012, tonnage was up 6.7%, representing the largest y-o-y gain since December 2011.

Year-to-date, the tonnage index is up 4.5% compared to the same time period last year.

“After bouncing around in a fairly tight band during the previous three months, tonnage skyrocketed in May,” ATA chief economist Bob Costello said. He said some of the increase is attributable to factory output rising in May for the first time since February (+0.2%) and retail sales performing stronger than expected in May (+0.6%).

Costello added, “The 6.8% surge in new housing starts during May obviously pushed tonnage up as home construction generates a significant amount of truck tonnage.”

“While we heard good reports regarding freight levels during May, I have to admit I am a little surprised at the large gain in tonnage,” Costello said. He added that tonnage continues to outpace the number of loads hauled as heavy freight (ie., housing construction materials and sand and water for hydraulic fracturing) is outperforming box trailer (ie., dry van) freight.