A key measure of truck capacity and demand dropped 10.7 percent last week, indicating some easing of over-the-road capacity constraints in mid-April.
In its second consecutive weekly decline, the April 19 Longbow Research Weekly Truckload Barometer dropped to 144.7 from 162 from the previous week.
Last week's drop was the largest decline in the index in recent months. The index moderated 5.7 percent in the month of March and rose rapidly in early April.
Even with the 10.7 percent drop, the index is at levels not seen since the second-quarter inventory restocking surge that launched a freight recovery in 2010.
Though it's backed off recent peaks, the Longbow index is still up 31.7 percent since the beginning of 2011, and is 17.9 percent higher than a year ago.
The index measures available freight against available equipment, climbing as capacity contracts and falling as more capacity becomes available.
"The Upper Midwest and Southeast are currently experiencing the tightest truckload capacity," trucking analyst J. Douglas Woodrich said in a note to investors.
Increased manufacturing in the Midwest and seasonal produce shipping in the Southeast are likely reasons for more intense demand for tractor-trailers.
Capacity also is tight in the Northeastern states of New York, Pennsylvania and New Jersey. The West has "more abundant" truckload capacity, Woodrich said.