Driver turnover at large and small truckload and less-than-truckload carriers rose in the first quarter on an improving economy, American Trucking Associations said.

Turnover at large truckload fleets in the US with more than $30 million in annual revenue rose to an annualized 97% rate from 90% in the fourth quarter.

Turnover at smaller truckload fleets rose to 82% from 76% in the previous quarter. The rate matches the 2012 average, but is below the most recent high of 84% in the third quarter of last year, according to ATA.

“Our data shows that competition for drivers across the industry remains high,” ATA Chief Economist Bob Costello said in a statement. “It is our fear that this competition for drivers may be exacerbated by losses in productivity caused by recent regulatory changes such as the new hours-of-service rules.”

In the LTL sector, turnover increased to 15% in the first quarter, the highest level since the fourth quarter of 2005, from 10% in the previous quarter.

“If the economy continues to improve as we expect it to,” Costello said, “we’ll see competition for drivers intensify, which will increase not just the turnover rate and exacerbate the driver shortage, but will push costs for fleets higher as well.”