ARLINGTON, Va., June 21, 2016 /PRNewswire-USNewswire/ -- American Trucking Associations' advanced seasonally adjusted (SA) For-Hire Truck Tonnage Index increased 2.7% in May, following a revised 1.7% drop during April. In May, the index equaled 139 (2000=100), up from 135.3 in April. The...