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4. Department of Transport, Local Government and the Regions, 2000. The Governments Response to the SACTRA Report on Transport and the Economy. www.dtlr.gov.uk/roadnetwork/sactra2/index.htm.
5. Department of Transport, Local Government and the Regions, 2001a. Transport Economics Note. www.roads.dtlr.gov.uk/roadnetwork/heta/ten00/pdf/ten00.pdf.