1. The 2015 Urban Mobility Report (2015) Texas A&M Transportation Institute, College Station, Texas. Available: http://mobility.tamu.edu/ums/report/
2. 2013 Status of the Nation’s Highways, Bridges, and Transit: Conditions and Performance (2014) National Technical Information Service, Federal Highway Administration, Federal Transit Administration. http://www.fhwa.dot.gov/policy/2013cpr/
3. Transportation Statistics Annual Report (2015) US Department of Transportation. 2015. http://www.rita.dot.gov/bts/publications/transportation_in_the_united_states_2015/index.html
4. Mass Mobility Reports: The Massachusetts Community Transportation Series 2013. Human Service Transportation Office. 2013. http://www.mass.gov/eohhs/gov/commissions-and-initiatives/hst/annual-reports.html
5. Urban rail transit in China. https://en.wikipedia.org/wiki/Urban_rail_transit_in_China . Accessed 28 Sept 2016