The Value of MXD+

Mixed-use development is widely considered an effective means of reducing traffic impacts. Ranking in the EPA Top 10 Smart Growth Planning Principles, mixing a variety of land uses is generally considered a strategy that optimizes use of transportation infrastructure, improves community quality-of-life, and reduces vehicle travel and related concerns over global warming. Therefore, it achieves higher levels of support from planners, policy makers, and elected officials and developers.

Mixed-use developments come in a wide range of sizes, mixes, and configurations. As one common characteristic, such development can reduce off-site traffic impacts by satisfying travel needs within the development site and reducing external travel. However, traffic engineers are ill-equipped to quantify these benefits in traffic planning and impact analysis. Techniques available from ITE and standard travel modeling do not accurately measure the potential trip reduction achievable from a full range of development concepts. Fehr & Peers developed a more accurate and robust method of estimating the traffic generation from mixed-use development projects. The approach relies on built environment variables known as the “D’s” to measure the degree of interactivity within the site and adjust the conventional ITE and modeling methods.

The latest MXD research shows that traffic studies overestimate impacts of mixed-use development by 35%. The new MXD+ 2.0 analysis tool corrects those errors, as described in the American Planning Association planning advisory, “Getting Trip Generation Right: Eliminating the Bias Against Mixed-Use Development.”