The series comes from the 'Current Employment Statistics (Establishment Survey)'
The source code is: CES4300000016
Source: US. Bureau of Labor Statistics
Release: Employment Situation
US. Bureau of Labor Statistics, Indexes of Aggregate Weekly Hours of All Employees: Transportation and Warehousing [CES4300000016], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/CES4300000016/, August 2, 2015.