Completed 2021 Research Project

Using Safe Systems approach to assess traffic impact and land development

Principal Investigator
Tab Combs
University of North Carolina, Chapel Hill
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Co-Principal Investigator
Eric Dumbaugh
Florida Atlantic University
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Final Report

Project Slide Deck

Interview Transcripts

Research Brief


Traffic impact analysis (TIA) is an important piece of transportation planning, design, and construction. The practice is conventionally deployed as a means to minimize and mitigate the traffic congestion impacts of new development by tying roadway capacity improvements to land development permits. Many city and state governments view the TIA process as a critical means of generating needed infrastructure improvements, and its use has become ubiquitous among DOTs across the US. However, there is a paucity of research into the relationship between land development and road safety outcomes. Prior work in the US southeast also suggest that current TIA practices in that region do not consider TIA’s direct impacts on road safety or its potential role in shaping safe systems. This project addresses these gaps by:

  1. evaluating whether, how, and the extent to which current TIA practices in the US southeast incorporate road user safety into assessments of impacts of land development or into strategies to mitigate those impacts;
  2. identifying opportunities to integrate safe systems concepts and metrics into the development review process; and
  3. advancing a new, safe systems-approach to estimating and minimizing the safety impacts of new land development.

Through a multi-stage qualitative analysis of interviews and focus groups with public and private sector TIA practitioners, we uncover and unpack self-defeating narratives about the complex relationship between safety and congestion. We also identify potential entry points within TIA practice for integrating safety-centered outcome metrics, and develop practical guidance for bringing TIA practice in closer alignment with safe systems concepts.

Project Details

Project Type: Research
Project Status: Completed
Start Date: 5/10/2021
End Date: 6/30/2022
Contract Year: Year 5
Total Funding from CSCRS: $94,701