An official website of the United States government
The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before
sharing sensitive information, make sure you’re on a federal
government site.
The site is secure.
The https:// ensures that you are connecting to the
official website and that any information you provide is encrypted
and transmitted securely.
Ivanov D.Ivanov D.Transp Res E Logist Transp Rev. 2020 Apr;136:101922. doi: 10.1016/j.tre.2020.101922. Epub 2020 Mar 24.Transp Res E Logist Transp Rev. 2020.PMID: 32288597Free PMC article.