7T. W. Welch. The Conversion of Four-Lane Undivided Urban Roadways to Three-Lane Facilities[J]. Transportation Research Broad, National Research Council, Washington, DC, 1999.
8Knapp, K. K., T. W. Welch, and J. Witmer. Converting Four-Lane Undivided Roadways to a Three-Lane Cross-Section: Factors to Consider[J]. Iowa State University, Center for Transportation Research and Education, 1999.
9Cao, C. The Conversion of a Four-Lane Undivided Roadway to a Three Lane with Center Two Way Left-Turn Lane (TWLTL) Cross Section[J]. Final Report for Civil Engineering 590(Independent Study), Unpublished Paper, Iowa State University, May 1999.
10Bonneson, J. A. , P.T. McCoy. Capacity and Operational Effects of Midblock Left-Turn Lanes[J]. Transportation Research Broad, National Research Council, Washington, DC , 1997.
