Investors interested in Transportation - Truck stocks are likely familiar with Knight-Swift Transportation Holdings (KNX Quick QuoteKNX - Free Report) and Old Dominion Freight Line (ODFL Quick QuoteODFL - Free Report) . But which of these two companies is the best option for those looking for undervalued stocks? Let's take a closer look.

There are plenty of strategies for discovering value stocks, but we have found that pairing a strong Zacks Rank with an impressive grade in the Value category of our Style Scores system produces the best returns. The Zacks Rank favors stocks with strong earnings estimate revision trends, and our Style Scores highlight companies with specific traits.

Knight-Swift Transportation Holdings and Old Dominion Freight Line are both sporting a Zacks Rank of # 2 (Buy) right now. Investors should feel comfortable knowing that both of these stocks have an improving earnings outlook since the Zacks Rank favors companies that have witnessed positive analyst estimate revisions. But this is just one factor that value investors are interested in.

Value investors are also interested in a number of tried-and-true valuation metrics that help show when a company is undervalued at its current share price levels.

The Value category of the Style Scores system identifies undervalued companies by looking at a number of key metrics. These include the long-favored P/E ratio, P/S ratio, earnings yield, cash flow per share, and a variety of other fundamentals that help us determine a company's fair value.

KNX currently has a forward P/E ratio of 12.31, while ODFL has a forward P/E of 32.67. We also note that KNX has a PEG ratio of 0.82. This popular figure is similar to the widely-used P/E ratio, but the PEG ratio also considers a company's expected EPS growth rate. ODFL currently has a PEG ratio of 1.49.

Another notable valuation metric for KNX is its P/B ratio of 1.31. The P/B ratio is used to compare a stock's market value with its book value, which is defined as total assets minus total liabilities. For comparison, ODFL has a P/B of 9.49.

Based on these metrics and many more, KNX holds a Value grade of A, while ODFL has a Value grade of D.

Both KNX and ODFL are impressive stocks with solid earnings outlooks, but based on these valuation figures, we feel that KNX is the superior value option right now.