1. Bureau of Transportation Statistics. Transportation economic trends. U.S. Department of Transportation; www.bts.gov/product/transportation-economic-trends Bureau of Transportation Statistics. Transportation economic trends. U.S. Department of Transportation; www.bts.gov/product/transportation-economic-trends
2. U.S. Bureau of Labor Statistics. American time use survey summary. United States Department of Labor . July 22, 2021 ; https://www.bls.gov/news.release/atus.nr0.htm U.S. Bureau of Labor Statistics. American time use survey summary. United States Department of Labor. July 22, 2021; https://www.bls.gov/news.release/atus.nr0.htm
3. Bureau of Transportation Statistics. New freight benchmark shows value, weight of goods moved on America's transportation network rose over a five-year period . February 26, 2021 . U.S. Department of Transportation ; https://www.bts.dot.gov/newsroom/new-freight-benchmark-shows-value-weight-goods-moved-americas-transportation-network-rose Bureau of Transportation Statistics. New freight benchmark shows value, weight of goods moved on America's transportation network rose over a five-year period. February 26, 2021. U.S. Department of Transportation; https://www.bts.dot.gov/newsroom/new-freight-benchmark-shows-value-weight-goods-moved-americas-transportation-network-rose