Dow transports are on a roll. Why investors shouldn’t ignore the bullish message.

There’s an often neglected part of the stock market sending a pretty bullish signal, and history suggests investors would be wise not to ignore it.

The Dow Jones Transportation Average

DJT is only 20 stocks, and the market capitalization of the largest component, Uber Technologies UBER, was just $191.5 billion in Monday trading — or about 4.3% the size of the S&P 500 index’s SPX biggest member, Nvidia NVDA, which was at $4.43 trillion.