EXECUTIVE SUMMARY

Traffic analysis tools play a critical role in prioritizing public investment in strategies employed by transportation professionals to relieve congestion. Use of traffic simulation and analysis tools has become the standard approach for evaluating transportation design alternatives, operational performance, Intelligent Transportation Systems (ITS) and traffic operations strategies.

The purpose of this study is to assess and provide an understanding on how well simulation and traffic analysis tools predict performance, and identify elements and issues which practitioners should be aware of to effectively apply these tools. In order to support recommendations for use by practitioners, information was gathered and five locations were chosen for in-depth analysis. These sites include:

1. I-494 and Trunk Highway 7 in Minneapolis, Minnesota: Analysis of proposed freeway segment and interchange improvements.
2. I-15 Reconstruction in Ogden, Utah: Analysis of maintenance of traffic and reconstruction closure scenarios.
3. S.R. 826-Palmetto Expressway Off-Ramps near Miami, Florida: Analysis of proposed off-ramp improvements and the addition of an auxiliary lane.
4. I-25 and University Boulevard in Denver, Colorado: Estimation of performance of replacing a full cloverleaf interchange with a single point urban interchange (SPUI).
5. Traffic Signal Network in Chicago, Illinois: Study of key issues in the validation of a microsimulation analysis of a complex arterial network signal timing project.

The five cases were selected to test a variety of software model tools across a range of applications and settings, illustrative of problems as well as best practices, to derive lessons learned. During these investigations, much was learned that increases the understanding of current practice and provides insights into improving future analyses. The summary and recommendations at the end of this report discuss examples of lessons learned, and how the modeling process can account for the types of modeling challenges identified. The information presented in the case studies, along with conclusions drawn from the analyses and experience of the authors, are the foundation for a practical set of guidelines and suggestions for overcoming common shortcomings, unreliable assumptions and similar problems. The checklist included as Attachment 1 provides a summary guide to a host of issues that contribute to deviations between simulations and observed conditions.