Amid this torrent of swirling economic uncertainties, there's nothing like a tangible quarterly result from a key bellwether industry to let investors know where they stand.

As the first of the major U.S. railroads to report third quarter earnings, CSX (NYSE: CSX) provides a welcome barometer of domestic economic activity. By reporting a 48% increase in earnings per share, atop only a 16% rise in revenue, CSX has set a lofty bar by which its peers will soon be measured.

In a rather awe-inspiring display of continued success in driving increasing operating efficiencies, CSX managed to cleave 490 basis points from its operating ratio over the prior-year result. The company's 69.1% operating ratio also marks a sequential improvement from an already-lean second quarter reading of 71.2%, though it's worth noting that competitors Norfolk Southern (NYSE: NSC) and Union Pacific (NYSE: UNP) already reported sub-70 figures of their own last quarter.

It is all too tempting to question how much more margin can be squeezed from the rails when the broader economic outlook appears to this Fool to be questionable at best, but I have learned my lesson the hard way never to underestimate these haulers' ability to defend their bottom lines. At last check, the pack was still chasing the unparalleled efficiency of Canadian National Railway (NYSE: CNI), with a second-quarter reading of just 61.2%.

Overall freight volume for CSX grew by 10% year-over-year, but came in nearly flat on a sequential basis. For any investors pining for signs of momentum in what had been widely viewed as an economic recovery mere months ago, even taking seasonality into consideration, I believe these freight data are destined to disappoint. Although CSX grew coal revenue by 23% over the prior year, coal volume expanded by only 3%. Intermodal and industrial sector freight categories, meanwhile, carried the day for CSX with improvements of 19% and 15%, respectively.

Looking to the railroad industry at large, we find all freight categories thus far in 2010 remaining substantially below comparable levels from two years ago. The most notable remaining impairments, unsurprisingly, reside in forest products and automotive freight.

Railroad stocks surged Wednesday in apparent response to CSX's robust earnings. For a broader read of domestic economic conditions that will impact the outlooks for this and other bellwether industries, however, Fools are encouraged to stay tuned for a high-stakes quarter of corporate earnings from particularly insightful bellwethers like Nucor (NYSE: NUE) and Peabody Energy (NYSE: BTU). We may discover, to our collective dismay, that those infamous sprouting green shoots were themselves a tough act to follow.

Fool contributor Christopher Barker can be found blogging actively and acting Foolishly within the CAPS community under the username TMFSinchiruna. He tweets. He owns shares of Nucor and Peabody Energy. True to its name, The Motley Fool is made up of a motley assortment of writers and analysts, each with a unique perspective; sometimes we agree, sometimes we disagree, but we all believe in the power of learning from each other through our Foolish community. The Motley Fool has a disclosure policy.