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.
Selected Awards
2018: Certificate of Appreciation in recognition of leadership in advancing the science of travel demand modeling, Committee on Transportation Demand Forecasting, Transportation Research Board
2016: Fellow, Chan Wui & Yunyin Rising Star Workshop for Early Career Professionals in Transportation
2013: Best Paper Presentation at the 14th Transportation Planning Applications Conference
2013: Best Paper Presentation at the 14th Transportation Planning Applications Conference
2012: Best Presentation at Futura 2012
2011: Best Presentation at Futura 2011
2009: Best Paper Presentation at the 12th Transportation Planning Applications Conference
2008: Professional Associate, Parsons Brinckerhoff
2000: Walter P. Murphy Engineering Fellowship
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.
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.
Erhardt, Gregory D.; Goyal, Vedant S.; Kressner, Josephine; Berrebi, Simon J.; Brakewood, Candace; Watkins, Kari E.: Simulating the effect of strategies to increase transit ridership by reallocating bus service: Two case studies. Journal of Public Transportation 26, 2024, 100080 more…
Moeckel, Rolf; Huang, Wei-Chieh; Ji, Joanna; Llorca, Carlos; Moreno, Ana Tsui; Staves, Corin; Zhang, Qin; Erhardt, Gregory D.: The Activity-based model ABIT: Modeling 24 hours, 7 days a week. Transportation Research Procedia 78, 2024, 499-506 more…
2023
Erhardt, G., Hensle, D., Bradley, M., Imarah, M., Freedman, J, Gardner, M., Stabler, B.: Estimating and Implementing a Vehicle-Type Model in an Activity-Based Travel Model Framework. Transportation Research Record, 2023, more…
Erhardt, Gregory D.; Han, Ke: Intersections Between Mobility and Communications. Networks and Spatial Economics 23 (2), 2023, 349-351 more…
Goyal, V.S., Erhardt, G.D., Stamatiadis, N., Bollinger, C.R.: Do transportation network companies increase or decrease road crashes? Evidence from San Francisco. Transportation Research Board Annual Meeting, 2023 more…
Hoque, J.M., Zhang, I., Schmitt, D., Erhardt, G.D.: “Are Public Transit Investments Based on Accurate Forecasts? An Analysis of the Improving Trend of Transit Ridership Forecasts in the United States”. Transportation Research Part A: Policy and Practice, 2023, more…
Hoque, J.M., Zhang, I., Schmitt, D., Erhardt, G.D.: Are Public Transit Investments Based on Accurate Forecasts? An Analysis of the Improving Trend of Transit Ridership Forecasts in the United States. Transportation Research Board Annual Meeting, 2023 more…
Moreno, A.T., Nouli, G., Ahmed, U., Schiffer, M., Moeckel, R.: Understanding the Impact of Life Events on Travel Behavior Change via Machine Learning. Euro Working Group Transportation , 2023 more…
Mucci, Richard (Alex); Erhardt, Gregory D.: Understanding Ride-Hailing Sharing and Matching in Chicago Using Travel Time, Cost, and Choice Models. Transportation Research Record: Journal of the Transportation Research Board 2678 (2), 2023, 293-306 more…
Zhang, I., Ashby, E., Erhardt, G.D: A disaggregate model of domestic migration in the United States. Transportation Research Board Annual Meeting, 2023 more…
