Tierra S. Bills is an Assistant Professor of Public Policy and Civil and Environmental Engineering at the University of California, Los Angeles. She specializes in the evaluation of transportation planning and system outcomes, and travel demand modeling, with a special emphasis on transportation equity. Dr. Bills brings a unique and innovative perspective to the challenge of transportation inequity, aimed at impacting transportation science, practice, and quality of life for vulnerable communities. She has worked in the transportation equity domain since 2009 and her current work builds off this track record, including her master’s research, dissertation work, study and training as a Research Scientist at IBM Research, Michigan Society Fellowship research, and previous work as a former Assistant Professor at Wayne State University.

Dr. Bills has extensive training in travel demand modeling and is engaged in ongoing work on representation of transport vulnerable travelers, in household travel surveys. These travel surveys are traditionally used to estimate and validate travel demand models and this is a pathway to developing travel models capable of reflecting the needs and behaviors of disadvantaged travelers and fine-grain transportation equity outcomes. Dr. Bills also works to advance accessibility measurement for transportation project evaluation, and develops strategies for ranking alternative transportation plans using equity-based criteria. 

At UCLA, Dr. Bills directs the Transportation Equity Innovation (TrEI) Lab, and leads a team of graduate and undergraduate students in developing innovative, meaningful, and effective tools for assessing fairness in transportation infrastructure, systems, and policies.  Dr. Bills is also affiliated with the UCLA Institute of Transportation Studies, UCLA Bunche Center, and collaborates with students, faculty, and researchers across engineering, policy, planning and other disciplines. Her team’s work is published in a range of journals including Transport Policy, Transportation Research Part D, Transportation,  and Transportation Research Record. 

Selected Publications

Srisan, T., & Bills, T. (2024). A Case for Race and Space in Auto Ownership Modeling: a Los Angeles County study. Transport Policy. (Link)

Bills, T. S. (2022). Advancing the Practice of Regional Transportation Equity Analysis: a San Francisco Bay area case study. Transportation, 1-26. (Link)

Bills, T. S., Twumasi-Boakye, R., Broaddus, A., & Fishelson, J. (2022). Towards transit equity in Detroit: An assessment of microtransit and its impact on employment accessibility. Transportation Research Part D: Transport and Environment, 109, 103341. (Link)

Bills, T. S., & Carrel, A. L. (2021). Transit accessibility measurement considering behavioral adaptations to reliability. Transportation research record, 2675(5), 265-278. (Link)

Bills, T. S., & Walker, J. L. (2017). Looking beyond the mean for equity analysis: Examining distributional impacts of transportation improvements. Transport Policy, 54, 61-69. (Link)

Bills, T. S., Sall, E. A., & Walker, J. L. (2012). Activity-based travel models and transportation equity analysis: Research directions and exploration of model performance. Transportation research record, 2320(1), 18-27. (Link)