Volvo Group reported earnings and net sales fell in the second quarter and six-month periods, citing the slowdown in the North American truck market as a key factor that led to a plunge in orders.

Landstar System Inc. net income tumbled 20%, hurt by a combination of weaker trucking results and accident costs, while Marten Transport Ltd. earnings rose 2.1%, helped by dedicated and intermodal results as well as gains on equipment sales.

Higher profit from dedicated truckload business helped J.B. Hunt Transport Services Inc. to eke out a 1.5% second-quarter net income increase to $105.1 million, or 92 cents per share, but weaker than expected intermodal unit performance and other factors led the company to lower its 2016 earnings expectations.

A series of weak second-quarter earnings reports in the weeks ahead should document evidence that truck freight markets have suffered this year amid excess capacity and overstocked inventory, analysts believe.

Greenbrier Cos. reported earnings of $35.4 million, or $1.12 per share, in the fiscal third quarter ended May 31, a 17.4% drop from the $42.8 million, or $1.33, in the prior year period.

Werner Enterprises Inc. said difficult rate negotiations, lower spot-market prices and other factors in a sluggish freight market would reduce its second-quarter earnings to a range of 21 cents to 25 cents per share, which is below the average estimate of 40 cents per share based on Bloomberg’s analyst survey.

Danish firm Maersk Group, owner of the largest ocean carrier, earlier this month reported first-quarter earnings plummeted nearly 90% to $224 million, weighed down by an even greater profit decline at Maersk Line due to downward pressure on container freight rates.