Session No. 3B

Project Applications Showcasing the Ins and Outs of Microscopic Simulation Models

Moderator: Keith Hartington, PTP, PMP, Manager of Transportation Studies, Delaware Valley Regional Planning Commission

VISSIM Analysis of Complex Construction Staging for I-70 at SR 0051 Diverging Diamond Interchange

  • Ashley Tracy, PE, PTOE, AICP, Senior Traffic Engineer, McCormick Taylor

COVID-19 Data Impacts to Calibration and Analysis

  • Silvia Scheuermann, PE, Deputy Department Manager/Senior Traffic Engineer, AECOM

The When and Why to Choose a Microsimulation Platform — A Comparison of Aimsun and VISSIM

  • Steve Speth, PE, PTOE, Senior Traffic Engineer, Senior Professional Associate, HDR, Inc.
  • Bryan St. George, Traffic and Transportation Engineer, HDR, Inc.


Ashley Tracy is a Senior Traffic Engineer at McCormick Taylor with 10 years of experience in traffic operational analysis and transportation planning. She graduated from Penn State in 2011 with a Bachelor’s degree in Civil Engineering and holds Professional Engineering licensure in Pennsylvania, Texas, and Florida, as well as PTOE certification. She strives to combine the “how” of engineering with the “why” of planning to help communities and improve transportation for all people, and earned her AICP-certification in 2020. She currently lives in Pittsburgh, Pennsylvania with her husband and cat, and enjoys gardening and painting in her free time.

Silvia Scheuermann, PE is a Deputy Department Manager for AECOM’s Greater PA Traffic and ITS Department as well as an alum of the Pennsylvania State University. Scheuermann has more than 10 years of experience in traffic analysis and design. In her three years at AECOM, she has worked on or reviewed VISSIM models for PennDOT District 6-0 and PennDOT District 5-0 projects including the I-80 Section 17M Reconstruction project, I-80 Section LBS Corridor Study and US 22 Widening project as well as the Port Authority of Allegheny County’s Bus Rapid Transit Project in Pittsburgh. Currently, Scheuermann is working on the I-81 Section D46 Reconstruction Project for PennDOT District 4-0 near Scranton.

Steve Speth has more than 23 years of experience in the in traffic engineering, with his specialty being traffic simulation modeling. He is based out of Springfield, NE, but has performed analyses as a national resource for traffic simulation. Speth has used several simulation software packages in the past, starting in CORSIM, but more recently using TransModeler, VISSIM, and Aimsun. Speth has worked on large projects in nearly every state and has specialized in modeling and design of complex intersections and interchanges, including large, congested freeway projects. One of the largest simulation models Speth was involved in was in Anchorage, Alaska. There was a need on the project to connect two major freeway systems that went through Anchorage. Aimsun is a tool that has become more popular in recent times, especially because of how it has Macro/Meso/Micro capability in one platform and due to its speed for runtime. Speth has recently used it on the Southern Nevada Traffic Study (SNTS). In this project, a full city model was built for the city of Las Vegas to analyze and assist in prioritizing corridor improvements. 

Bryan St. George has more than seven of experience in the industry, focusing primarily on traffic analysis. He is based out of Tampa, Florida, and has performed analyses throughout the US and Australia using a variety of simulation software, such as CORSIM, VISSIM, and Aimsun. St. George has used CORSIM to model over 11 miles of I-275 in Pinellas County, Florida to test the phased implementation of managed lanes along the interstate. In Durham, North Carolina, St. George used VISSIM software to model traffic operations within Downtown Durham before and after the implementation of Light-Rail Transit (LRT). In Hastings, Minnesota, St. George used VISSIM to perform alternatives testing along the TH 316 corridor. Aimsun has become an increasingly popular software that can be used in all stages of traffic analysis. St. George has used Aimsun on several projects in Hillsborough County, St. Petersburg, and two suburbs of Tampa — Brandon, and Gibsonton, Florida.


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Dec. 9, 2021

10:00 to 11:15 a.m.




The Transportation Engineering and Safety Conference (TESC) attracts professionals from throughout Pennsylvania, the mid-Atlantic region, and the country. It is an authoritative source of information on pressing issues from some of the foremost experts in transportation today.

Thomas D. Larson Pennsylvania Transportation Institute

201 Transportation Research Building

The Pennsylvania State University

University Park, PA 16802-4710

Phone: 814-865-1891