American Trucking Assns. (ATA) advanced seasonally adjusted for-hire truck tonnage index fell 3% in April, following a revised gain of 0.4% during the previous month. In April, the index equaled 128.6 (2000=100), which was the lowest level since April 2014. The all-time high is 135.8, reached in January 2015.Compared with April 2014, the SA index increased just 1%, which was well below the 4.2% gain in March and the smallest year-over-year gain since February 2013. Year-to-date through April, compared with the same period last year, tonnage was up 3.8%. The not seasonally adjusted index, which represents the change in tonnage actually hauled by the fleets before any seasonal adjustment, equaled 130.6 in April which was 5.9% below the previous month (138.7). “Like most economic indicators, truck tonnage was soft in April,” ATA chief economist Bob Costello said. “Unless tonnage snaps back in May and June, GDP growth will likely be suppressed in the second quarter.” Costello added that truck tonnage is off 5.3% from the high in January. “The next couple of months will be telling for both truck freight and the broader economy. Any significant jump from the first quarter is looking more doubtful,” he said.Trucking serves as a barometer of the U.S. economy, representing 68.8% of tonnage carried by all modes of domestic freight transportation, including manufactured and retail goods. Trucks hauled just under 10 billion tons of freight in 2014. Motor carriers collected $700.4 billion, or 80.3% of total revenue earned by all transport modes. ATA calculates the tonnage index based on surveys from its membership and has been doing so since the 1970s. This is a preliminary figure and subject to change in the final report issued around the 10th day of the month. The report includes month-to-month and year-over-year results, relevant economic comparisons and key financial indicators.