2013 has been a strong year for shares of Union Pacific ( UNP). Shares of the $70 billion railroad stock have rallied almost 19% this year, buoyed by overall strength in the transports sector. UNP is the largest railroad on the continent, with more than 32,000 miles of track that links 23 states, Canada and Mexico. That scale puts the firm in a strong position to grab more freight volume as the economy warms up. >>5 Stocks Poised for Breakouts While oil prices have dipped recently, they're still on the high end of their historic range, and that actually bodes well for railroads. In general, rail shipping costs around one-fourth as much as trucking does per ton shipped, a cost advantage that typically sends customers setting aside the convenience factor of truck freight once fuel prices get past a certain point. The firm's hefty commodity exposure is a little less attractive right now, but that hasn't stopped Union Pacific from posting impressive revenue numbers lately. UNP has a deep economic moat. Railroad assets aren't easily copied by rivals - and they're extremely costly to maintain. While that does mean that UNP has some hefty fixed costs to overcome, its scale easily makes up for that drawback. With much better efficiency than the firm had just a couple of years ago, Union Pacific looks well positioned for 2013. We're betting on shares of this Rocket Stock this week.