Safe-D: Safety through Disruption

Development of Analytic Method to Determine Weaving Patterns for Safety Analysis near Freeway Interchanges with Access Management Treatments (TTI/TAMU)



This project supports a student in support of the National Cooperative Highway Research Program (NCHRP) Project 07-23 Access Management in the Vicinity of Interchanges and was led by Karen Dixon (TTI/TAMU)* and Maryam Shirinzadeh Dastgiri (TAMU). This project used a large volume of operational field data, micro-simulation data, and crash data to identify linkages between interchange design, driveway placement, and upstream major intersection location that affect corridor safety. The effort primarily focused on the diamond interchange configuration that is very common in the United States. The methods for determining corridor safety near interchanges can create challenges. Due to the large traffic volumes, varying travel times, widely varying geometric features of the interchange, and a variety of access management scenarios, it is a challenge to assess the data and determine if safety performance issues should be attributed to the interchange traffic, the driveway traffic, the upstream intersection traffic, or a combination of these operational features blended with the prevailing corridor geometrics. These unknown issues make improving safety at these locations a challenge. For this effort, the student used field collected travel time and volume information to develop validated micro-simulation models that depict actual site conditions. Each location will then undergo a safety assessment to identify what factors appear to be correlated with safety performance. These “base” models will then be modified to change access management techniques (add or change medians, increase or decrease access density, shorten or lengthen distance to nearest major intersection) and then assess how minor changes may influence the operational performance. Though safety cannot be directly extracted from this micro-simulation activity, performance measures attributed to safety for the “base” models will be identified and evaluated using sensitivity analysis for the resulting large volume of data. The student funded by Safe-D is working with data collected for NCHRP project 07-23 but she is providing an added value by developing a method for determining vehicle weaving patterns in these interchange regions. This activity goes beyond the scope of the NCHRP project but builds upon it. The student’s work requires data mining using simulation data, video data, and travel time data (in some cases all merged together).

*This Project also goes by the title Using Big Data to Assess Corridor Safety Performance at Approaches to Freeway Interchanges

Project Highlights

  • This study investigated the operational safety of these elements and tries to find the relationship between geometric elements of the roadway and the operational safety of urban arterials near interchanges.
  • The project was able to complete two major data linkage tasks within a tight timeframe (approx. 1 year): travel diaries with GPS traces and GPS traces with roadway speed limits.
  • This project was completed by a multidisciplinary team: urban planners, civil engineers, and an epidemiologist.

Final Report

TTI-Student-02 Report

EWD & T2 Products

Student Impact Statement – Maryam Shirinzad (pdf): The student(s) working on this project provided an impact statement describing what the project allowed them to learn/do/practice and how it benefited their education.


Presented at the TUC Student Leadership Development Seminars Series, October 10, 2019

Final Dataset

The final dataset was used by permission from an NCHRP project and will not be shared.

Research Investigators (PI*)

Karen Dixon (TTI)*

Maryam Shirinzadeh Dastgiri (TAMU)

Project Information

Start Date: 01/01/2017
End Date: 01/10/2018
Status: Complete
Grant Number: 69A3551747115
Total Funding: 
Source Organization: Safe-D National UTC
Project Number: TTI-Student-02

Safe-D Theme Areas

Big Data Analytics

Safe-D Application Areas

Planning for Safety

More Information


Sponsor Organization

Office of the Assistant Secretary for Research and Technology
University Transportation Centers Program
Department of Transportation
Washington, DC 20590 United States

Performing Organization

Texas A&M University
Texas A&M Transportation Institute
3135 TAMU
College Station, Texas 77843-3135