A stubborn shortage of truck drivers ranks as the top concern of trucking fleets for the third year in a row, according to trucking industry research group The American Transportation Research Institute (ATRI).

Fleets are struggling to recruit and retain qualified drivers, according to Arlington, Virginia-based ATRI's annual "Top Industry Issues" report, which included more than 2,000 survey responses from motor carriers and commercial drivers.

The second greatest concern was hours of service (HOS) rules, which also repeated its rank from last year's report. Third on the list was driver compensation—which has risen in accordance with the driver shortage trend, but still may not be keeping up with inflation—followed by detention or delay at customer facilities, at fourth.

The detention issue reflects fleets' growing concern over excessive delays that create cascading impacts for drivers' hours-of-service compliance, compensation, and ability to find safe, available truck parking, ATRI said.

And the fifth issue on the top-five list was a lack of available truck parking, ATRI said when it released the findings of the survey during the 2019 American Trucking Associations' (ATA) Management Conference and Exhibition in San Diego.

"While 2018 was an incredible year for trucking, we've seen some challenges in 2019 and certainly finding and retaining qualified drivers remains at the top of the list for our industry," Barry Pottle, ATA chairman and president and CEO of Pottle's Transportation, said in a release. "ATRI's analysis reveals the interconnectedness of these top issues and provides a roadmap for how motor carriers and professional drivers believe we should move forward as an industry."