The turnover rate at U.S. truckload fleets increased during the first three months of 2017 while remaining at historically low levels, according to the American Trucking Associations.

In the first quarter of 2017, the annualized turnover rate at large truckload fleets, defined as those with revenues greater than $30 million, rose three percentage points to 74%. Despite the increase, turnover is still at a very low level and is 15 percentage points lower than at the same time last year.

“The slight uptick in turnover, despite weak freight volumes in the first quarter, may be indicative of a tightening in the driver market,” said Bob Costello, ATA chief economist. “The situation bears watching because if the freight economy picks up significantly, turnover will surely accelerate – as will concerns about the driver shortage.”

At small truckload fleets, turnover increased two points to 66%, 22 points lower than it was a year ago. The turnover rate at less-than-truckload carriers is typically very low and has increased two points to 10% in the first quarter.