Truck tonnage fell in May, most likely due to supply-chain interruptions and higher oil prices. Calculated Risk has more details. I offer this updated chart to show how closely the stock market, not surprisingly, tends to follow the ups and downs of the physical economy. I also note that truck tonnage is a very real indicator of economic growth, and can't be artificially elevated by cheap money or misguided stimulus programs.
Trucking serves as a barometer of the U.S. economy, representing 67.2% of tonnage carried by all modes of domestic freight transportation, including manufactured and retail goods.
It's reasonable to expect that supply-chain disruptions are now fading, and that, combined with a 20% drop in crude oil prices over the past two months, should allow somewhat stronger growth to resume in coming months.