Center for Transportation Research and Education

About the research

Each year a city public works focus group is convened the day before the spring conference of the Iowa Chapter of the American Public Works Association (APWA). Approximately five years ago, an idea was proposed at this focus group that responded to an identified need for more useful guidance related to the overall and elemental conversion of four-lane undivided roadway to three lanes (i.e., one lane in each direction and a two-way left-turn lane [TWLTL]). A literature review by the Iowa Department of Transportation (DOT) showed that a significant amount of material has been created on this subject. In fact, there has been so much documentation that it can be a challenge to practitioners. It was concluded by the project development team there was a need to combine this information in a more useful manner. The tasks in this project were designed to respond to this continuing need.