Second quarter performance for less-than-truckload carrier Old Dominion Freight Line improved from the year-ago quarter on a 13.4 percent boost in tonnage.

The company's revenue grew 16.5 percent for the quarter to $368.3 million from $316.2 million for the second quarter of 2009. Net income was $21.5 million, or 58 cents a share, for the second quarter of 2010, compared with $10.7 million, or 29 cents a share, for the second quarter of 2009.

"We are encouraged by the strength of our second-quarter operating results compared to the second quarter of 2009 and with the improving trends in our revenue and tonnage growth," said David S. Congdon, president and CEO. "As a result of our tonnage growth, we generated substantial operating leverage during the second quarter and first half of 2010 that was primarily responsible for doubling our earnings per diluted share for those periods."

Despite the improvements, Congdon said the company is still taking a conservative approach to the quarters ahead.

"Although we are seeing considerable strength in revenue and tonnage thus far in July, our outlook remains somewhat cautious for the second half of 2010," he said. "We remain uncertain about the strength and sustainability of the economic recovery as well as the potential impact from regulatory changes affecting, among other issues, healthcare, energy, labor and taxes."