Walls's current research focuses on issues related to urban land use, open space, and transportation. She has analyzed transferable development rights programs for managing land use in urban fringe areas, assessed the value of different types of parks and open space, and evaluated telecommuting in urban areas.  Walls also currently works on issues related to climate and energy policy and has published numerous articles on solid waste and recycling. Her work has appeared in the Journal of Public Economics, National Tax Journal, Journal of Urban Economics and Journal of Environmental Economics and Management, among others. 

Walls was a Fellow at RFF from 1987 to 1996. She then spent nearly five years in New Zealand as an associate professor of economics at Victoria University of Wellington. Walls rejoined RFF in November 2000.