Greg Erhardt

Global Visiting Professor, Hans Fischer Fellow, Institute for Advanced Study

Technical University of Munich, Germany; Institute for Advanced Study (Lichtenbergstrasse 2 a, D-85748 Garching, Germany)

Associate Professor, Department of Civil Engineering, University of Kentucky

Associate Director, T-SCORE Center

Phone: +49 (0) 172 623 9184

Phone: +1 859 323 4856




Dr. Greg Erhardt is an associate professor of civil engineering at the University of Kentucky.  He also serves as Associate Director for the T-SCORE Center, a consortium of four US universities that aims to define strategic visions to guide public transit into the future and equip planners with tools—including integrated optimization and simulations models--to translate visions into reality.  He earned his PhD from the Centre for Advanced Spatial Analysis (CASA) at University College London, a unique program that integrates engineering, geography, computer science, and complexity theory with a common focus on the science of cities.  Prior to earning his PhD, Dr. Erhardt spent 13 years in practice working in the public and private sectors in the US and the UK.  He holds a master’s degree in transportation systems analysis from Northwestern University and a bachelor’s degree in environmental engineering from Cornell University. 

Research Interests

Greg Erhardt aims to provide the information necessary to make smart decisions about transportation infrastructure investments and about how to best incorporate new technology into the existing transportation system. He does this by developing more sophisticated modeling tools to forecast the effects of proposed projects, analyzing new and emerging data sources to understand the effects of past projects, and combining both in support of evidence-based policy decisions. He is an active proponent of diversity and inclusion in engineering and is currently leading an initiative to train allies for gender equity.

For current projects and people, see my personal homepage.

Selected Publications

Public Transit and Ride-Hailing

Erhardt, G.D., Hoque, J.M., Goyal, V., Berrebi, S., Brakewood, C., Watkins, K. (2022) “Why has public transit ridership declined in the United States?”, Transportation Research Part A: Policy and Practice, Vol. 161.

Erhardt, G.D., Mucci, R.A., Cooper, D., Sana, B., Chen, M., Castiglione, J. (2021) “Do transportation network companies increase or decrease transit ridership? Empirical evidence from San Francisco”, Transportation.

Roy, S., Cooper, D., Mucci, R.A., Sana, B., Chen, M., Castiglione, J., Erhardt, G.D. (2020) “Why is Traffic Congestion Getting Worse?  A Decomposition of the Contributors to Growing Congestion in San Francisco and Determining the Role of TNCs”, Case Studies on Transport Policy, Vol 8, No. 4.

Erhardt, G.D., Roy, S., Cooper, D., Sana, B., Chen, M., Castiglione, J. (2019) “Do Transportation Network Companies Decrease or Increase Congestion?”, Science Advances, Vol 5, No. 5.

Transportation Forecast Accuracy

Hoque, J.M., Erhardt, G.D., Schmitt, D., Chen, M., Wachs, M., (2021) “Estimating the Uncertainty of Traffic Forecasts from Their Historical Accuracy”, Transportation Research Part A: Policy and Practice, Vol. 147.

Hoque, J.M., Erhardt, G.D., Schmitt, D., Chen, M., Chaudhary, A., Wachs, M., Souleyrette, R. (2021) “The Changing Accuracy of Traffic Forecasts”, Transportation.

Mucci, A. and Erhardt, G.D. (2018) “Evaluating the ability of transit direct ridership models to forecast medium-term ridership changes: Evidence from San Francisco”, Transportation Research Record, No. 2672. 

Big Data in Transportation Planning

Sana, B., Zhang, X., Castiglione, J., Chen, M., Erhardt, G.D., (2022) “Using Probe-Based Speed Data and Interactive Maps for Long-term and COVID-era Congestion Monitoring in San Francisco”, Transportation Research Record.

Erhardt, G.D., Batty, M., Arcaute, E. (2018) “Recommendations for Big Data Archival Programs at Transportation Agencies”.  In Big Data for Urban and Regional Science, edited by L.A. Schintler and Z. Chen, 292-303, Routledge. 

Erhardt, G.D. (2016) “How Smart is Your Smart Card?  Evaluating Transit Smart Card Data with Privacy Restrictions and Limited Penetration Rates”, Transportation Research Record, No. 2544.

For additional publications, see my Google Scholar Profile.