The Dow Jones Transportation Average (DJTA, also called the "Dow Jones Transports") is a U.S.stock market index of the transportation sector, and is the most widely recognized gauge of the American transportation sector. It is the oldest stock index still in use, even older than its better-known relative, the Dow Jones Industrial Average (DJIA).
The index is a running average of the stock prices of twenty transportation corporations, with each stock's price weighted to adjust for stock splits and other factors. As a result, it can change at any time the markets are open. The figure mentioned in news reports is usually the figure derived from the prices at the close of the market for the day.
Changes in the index's composition are rare, and generally occur only after corporate acquisitions or other dramatic shifts in a component's core business. Should such an event require that one component be replaced, the entire index is reviewed.