By Ron Rowland, contributing editor Money & Markets

One sector that is deeply intertwined with economic recovery is transportation. We live in a mobile society, even if we are in the internet age.

Not only do we move ourselves around, we also depend on quick, efficient transport to sustain our advanced economy.

Ever wonder how your neighborhood grocery store keeps fresh fruit and vegetables year-round? Transportation, that's how.

Food doesn't just magically move itself from wherever it grows to wherever you are. Someone has to haul it — by truck, railroad, ship, or airplane. And even when you shop online, those purchased products must be delivered.

Watching transportation stocks is a good way to keep an eye on the overall health of the economy. When demand starts to pick up, transport companies have to get busy moving stuff around.

Remember, a lot of stuff has to be moved before consumers actually buy it. That means the transportation companies are among the first to benefit from economic recovery. When the transports take off, there's a good chance the rest of the economy won't be far behind.

It works the other way around, too. When business slows down, merchants cut back their orders. Next thing you know, ships are sitting idle in ports and trucks are driving around half-empty. This is often apparent long before manufacturers and distributors see their own volumes drop.

So how can you play the transport sector? I have a suggestion for you ... Exchange-traded funds (ETFs) offer a quick and easy way to get exposure to most market sectors.

Transports are, I must say, a little bit underserved. Currently U.S. investors have access to only one broad transport sector ETF, and three more specialized offerings.

One reason for this is that stocks don't always fit into neat categories. Consider Boeing (BA). They make airplanes that are used by transportation companies. But Boeing's biggest customer, by far, is the U.S. government along with foreign military forces. So is Boeing a transport stock, a defense stock, or both? It's not easy to say.

Most index providers classify the transports as a subset of the "industrial" sector. If you buy SPDR S&P Industrials (XLI), for example, you'll have a piece of conglomerates like General Electric as well as transport stocks like FedEx and Union Pacific. You'll have Boeing, too.

If you want to zero in specifically on the transportation stocks, the best choice is iShares Dow Jones Transportation Average Index Fund (NYSE: IYT). This is an ETF that follows the venerable Dow Transports index, which includes 20 of the top U.S. railroads, truckers, delivery services, airlines, and shipping companies.

In addition to IYT, there are three ETFs that cover more specific niches within the transportation sector:

• Claymore/NYSE Arca Airline ETF (NYSE: FAA) holds airline stocks. This is a particularly volatile niche. Airlines regularly face vicious competition, rising fuel costs, and labor unrest. Yet these stocks can truly fly when conditions are right. Since its inception on January 26, 2009, FAA has lagged IYT, but it has started to come on strong the past six months.

• Claymore Delta Global Shipping Index ETF (NYSE: SEA) holds stocks from around the world that are involved in maritime freight transportation. SEA outperformed both FAA and IYT the past year and has been surging the last few weeks, but it is still far below its 2008 peak.

• PowerShares Global Progressive Transportation Portfolio (NASDAQ: PTRP) holds stocks that are involved in the quest for environmentally-friendly means of transportation. This excludes most of the large, well-known industry players. PTRP had the misfortune to be launched in late 2008 just as financial markets began to crater. But it has since recovered nicely.

Should you buy any of the transport ETFs right now? That's for you to decide. But under the right circumstances, this sector can give you amazing results. So keep your eye on the transports.

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