Trains, planes and trucks are rebounding. That's a good sign for the US economy

New York(CNN Business) When people are going places and goods are being shipped from point A to point B, that's the sign of a healthy economy. We're not there just yet, but there are nascent indications of a turnaround.

Transportation stocks -- airlines, railroads, truckers and shippers -- are a proverbial canary in a coal mine. The Dow Jones Transportation Average (DJT) is often looked at by experts as a good indicator for the state of the economy and broader market. And it's outperforming the market lately.

This index, which includes Southwest (LUV), Union Pacific (UNP), Old Dominion Freight Line (ODFL), FedEx (FDX), UPS (UPS) and fifteen other transportation stocks, nosedived in early March.

That was a clear sign at the time that there was more trouble looming for Main Street and Wall Street as the Covid-19 outbreak hit the United States.

But now these stocks are among the leaders in the current market rebound. The Dow Jones Transportation Average has surged more than 12% in just the past month, compared to about an 8% gain for the Dow 30 and S&P 500.

Transportation stocks have also done slightly better than the tech heavy Nasdaq as well as financial services and health care stocks.

"We are...seeing a secular rotation from stocks that have benefited from the shelter-in-place lockdown to stocks that will benefit from the recovery, including airlines, cruise lines, retailers, and other consumer-related companies," said Ivan Feinseth, chief investment officer of Tigress Financial Partners, in a report last week.

The hard-hit airlines have surged on hopes that travel demand could soon recover. Delta (DAL) said in mid-May that it was planning to return 100 international flights to its schedule this month, for example. And United (UAL) said it was seeing some "moderate" signs of a recovery last month too.

The recovery in airline stocks is all the more remarkable when you consider that investing guru Warren Buffett announced last month at the Berkshire Hathaway (BRKB) shareholder meeting that his firm has sold its stakes in Delta, Southwest, United and American (AAL).

But the truckers and railroads in the index are surging too, which might be a sign that the overall economy is starting to stabilize.

The sector remains fraught with risk -- and traders may be trying to take advantage of short-term pops. The top performer in the transportation index recently has been rental car company Avis Budget (CAR), which has surged more than 70% in the past month despite the bankruptcy of rival Hertz (HTZ).