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Highway Project Before and After Studies: Are We Improving What We Want to Improve?


Under a performance management framework, transportation investments need to be monitored to determine how well they achieve project objectives. The conditions/impacts of greatest interest are those that contribute to national performance metrics (e.g. congestion, travel time reliability, safety, and operational/maintenance costs). This project will look at methodologies used by DOTs and other transportation agencies around the nation to measure conditions before and after construction of highway infrastructure improvement projects.


The synthesis will survey state DOTs, MPOs/RPOs, tolling agencies, and other transportation agencies to gather information about how they measure project impacts. The survey will include information about:

  • The specific performance attribute being measured (crashes, delay, travel time reliability, operational cost, maintenance costs, etc.).* The determination of study bounds
  • The equipment needed to collect data
  • The data collection procedure
  • The data analysis procedure
  • The reporting format and frequency
  • The effectiveness/accuracy of the results

In addition, the project will draw from existing work, some of which is listed in the Information Sources section. The final synthesis will combine the survey results with the results of previous research and group similar measurement methodologies.


By summarizing the various methodologies, transportation agencies will be provided additional tools to measure the impacts of different projects (and ultimately different project types) towards achieving their agency’s performance measure targets. The synthesis will provide enough information for other transportation agencies to replicate the measurement methodology.

Related Research:

The citations included herein are limited to those studies that focus on the methodology of conducting before and after studies, the search does not include research where before and after studies were used to study a transportation improvement. In other words, citations for research studies, i.e., ‘Before-After Evaluation of Realignment of Horizontal Curves’, and ‘Before and After Evaluation of Transportation Infrastructure Improvements Using High-Resolution Transit Data’ are not included in this literature search.

Active Project: Evaluation of Safety Improvement Projects and Countermeasures

Texas A&M University, start date 09/01/2017, expected completion date 08/31/2019.

Completed Research:

  1. Identifying Net Effect of Highway Project in Before-and-After Evaluation. TRB 93rd Annual Meeting Compendium of Papers, 2014, 19p. http://docs.trb.org/prp/14-1404.pdf
  2. Interactions Between Transportation Capacity, Economic Systems, and Land Use. SHRP 2 Report, Issue S2-C03-RR-1, 2012, 62p. http://www.trb.org/Publications/Blurbs/166934.aspx
  3. Estimating the Variance in Before-After Studies. Ye, Zhirui and Dominque Lord, Journal of Safety Research, Volume 40, Issue Number 4, 2009, pp.257-263. http://dx.doi.org/10.1016/j.jsr.2009.04.004
  4. Empirical Bayes Before-After Safety Studies: Lessons Learned from Two Decades of Experience and Future Directions. Persaud, Bhagwant N and Craig Lyon, Accident Analysis & Prevention, Volume 39, Issue Number 3, 2007. http://www.sciencedirect.com/science/article/B6V5S-4M7VB89-1/2/664e1481aabc5b618773f9a473c0539e
  5. Common Bias in Before-and-After Accident Comparisons and its Elimination. Hauer, Ezra and Bhagwant Persaud. Transportation Research Record, Issue 905, 1983. http://onlinepubs.trb.org/Onlinepubs/trr/1983/905/905-027.pdf

Appropriate for MS or Ph.D. research or NCHRP Synthesis project

Sponsoring Committee:AEP10, Transportation Policy and Processes
Research Period:6 - 12 months
Research Priority:High
Date Posted:01/02/2020
Date Modified:03/09/2020
Index Terms:Before and after studies, Performance measurement, Project management, Construction projects, Highways,
Cosponsoring Committees: 
Administration and Management
Planning and Forecasting

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