Used Class 8 same-dealer truck sales volumes took a steep downturn in May, declining by 18% compared to April, according to ACT Research.

Year-to-date comparisons were more favorable, but still negative, as used Class 8 truck sales volumes fell by 5% compared to the same five-month period in 2015. Sales were down by as much as 10% compared to May 2015.

ACT attributed some of the decline to the usual seasonal drop-off that occurs this time of year.

The average price of used trucks was flat month-to-month and the average age increased.

“All three market segments saw declines, with auction and wholesale hit the hardest,” said Steve Tam, ACT's vice president of the commercial vehicle sector. “Dealers are reporting that used truck inventories continue to be high and are causing used truck prices to continue falling.”

ACT provides data on used truck sales based on a sample of industry data for each major truck OEM, including Freightliner, Kenworth, Peterbilt, International, Mack and Volvo.