NEW YORK ( TheStreet) -- Old Dominion Freight Line ( ODFL) is among Wednesday's earnings winners, with shares of the transport stocks rising more than 6%, and trading in its shares -- at 736,000 shares traded -- almost three times as high as its daily average trading volume before the midday mark.

It's been a big season of earnings beats for transportation stocks, from shipping companies to the big railroad operators, and Old Dominion kept the transport earnings outperformance alive. It's a trend among transport stocks earning that reflects the operational leverage this sector has when an economy is rebounding, explained Lee Klaskow, analyst at Longbow Research. This operational leverage is also helped by the fact that the year-over-year comparisons are easy beats for the transport stocks based on the conditions in 2009.

Old Dominion reported that second-quarter net income doubled and its tonnage hauled increased by 13%, ahead of Longbow Research's expectation of an 11% increase in tonnage. Notably, the tonnage increase occurred for the first time in two years.

The 58 cents per share earnings from Old Dominion was well ahead of the Street expectation of 46 cents, and dwarfed the year ago comparison, when the freight carrier earned 29 cents a share.

Old Dominion revenue rose 17% to $368.3 million, beating the Street's consensus revenue call of $359 million.

Earnings from rail operators including Union Pacific ( UNP) and Norfolk Southern ( NSC) have exceeded expectations, as well as results from United Parcel Service ( UPS).

The rebound in Old Dominion and the transport sector more generally outweighed a partially cautious outlook from Old Dominion in its earnings statement.

"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," Old Dominion said in its earnings statement. "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."

The Longbow Research analyst downplayed the outlook, saying that the commentary from Old Dominion management was merely covering all the bases of potential macroeconomic headwinds. "They're just stating the obvious," the analyst said. On a company-specific basis, the outlook was much more positive, with its tonnage gains expected to continue.

Indeed, Old Dominion also provided this outlook: "We anticipate tonnage to increase in a range of 15% to 20% for the third quarter compared with the third quarter of 2009."

"People underestimated the operating leverage of asset-based transport companies coming into earnings," Klaskow said.

Some investors read the early results from the rail sector as a read-through and reason to bid up transport stocks. However, in the case of Old Dominion, the company may not be a read-through for other truckers in terms of its earnings beat.

Old Dominion benefited from its pricing strategy, in particular, according to Longbow's Klaskow. He explained that while many truckers gave pricing concessions during the week 2009 conditions, Old Dominion's pricing strategy was more disciplined, and that has begun to pay off. "It's not a sign that all the truckers will outperform," the analyst said.

Most of the other trucking stocks were down on Wednesday morning.

-- Written by Eric Rosenbaum from New York.

RELATED STORIES:

Follow TheStreet.com on Twitter and become a fan on Facebook.
Copyright 2009 TheStreet.com Inc. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.