The link between the Dow Jones Transportation Average and the more-familiar Dow Jones Industrial Average is as old as the hills. If the indices are moving higher in tandem, the U.S. economy is perceived to be doing well because industry is making and transports are taking. However, should the transports start falling, especially ahead of similar moves in the industrial average, then the perception is that the economy is slowing because shipping demand, historically a leading economic indicator,...
https://www.freightwaves.com/news/does-the-decline-in-dow-transports-tell-us-anything