Cynthia Hoyle is a Life Member of the Sierra Club having joined the club in 1983 working to create the Tallgrass Prairie Preserve in Oklahoma. After moving to Illinois, she worked with the Prairie Group as Vice Chair and on the Transportation Committee. She served on the national Stopping Sprawl Campaign and the Clean Transportation for All Healthy Communities Campaign. She was a member of Urban Infill Policy Task Force which produced the Guidance for Smart Growth and Urban Infill Policy in 2021.
She has served on the American Institute of Certified Planners Commission, American Public Transit Association Climate Change Standards Working Group, and the Champaign County Blue Ribbon Environmental Panel. Cynthia is a Fellow of the American Institute of Certified Planners and is the author of Traffic Calming published by American Planning Association. She is a League Certified Instructor through the League of American Bicyclists and President of Ride Illinois.