Trucking industry analysts say a deep decline in truck orders this summer is the result of a big backlog from record-high orders U.S. companies placed over the past year.

FTR, a transportation equipment research group, reported Friday that trucking companies placed 19,550 net orders for heavy-duty trucks in August, the lowest level since September 2013, based in the group’s preliminary estimate.

That was 18% behind the July orders and 44% off the 2015 high of 35,000 orders in January.

Don Ake, vice president for commercial vehicles at FTR, said trucking companies and manufacturers effectively are pausing after a large number of orders trucking companies placed in the second half of 2014. He said companies have placed 350,000 orders over the past 12 months, including record orders in last year’s fourth quarter.

“This is a great year for the Class 8 (heavy-duty) truck industry,” said Mr. Ake. “We built up a huge backlog that went out through the fourth quarter of this year. We knew orders would start to moderate.”

Read more here.