Decision Tool to Define and Quantify Interchange Complexity

Because complexity typically is a qualitative characteristic, the ability to evaluate the complexity of an interchange objectively is somewhat difficult. This difficulty is compounded when trying to compare the complex features of multiple interchanges. A spreadsheet-based decision tool that was developed as a method for the quantification and comparison of the complexity of freeway interchanges in the United States is discussed. The initial discussion focuses on the steps that guided researchers in the development of the spreadsheet, and this discussion is followed by a description of the spreadsheet itself and how practitioners can use it to evaluate the complexity of interchanges under their consideration. A review is provided of the results researchers obtained with the spreadsheet in an evaluation of the complexity of 28 existing interchanges in 11 states. These study sites ranged from relatively simple to complex, and results indicated that the spreadsheet-generated scores were generally consistent with researchers’ qualitative estimates of the sites’ relative complexity. The meaning and interpretation of the spreadsheet results are discussed.