Kostelec is a consultant who specializes in planning and designing for original transportation. He began his career at Chicago Transit Authority and worked at Ada County Highway District from 2002 to 2008 before moving back to his native North Carolina to work in consulting for eight years. He returned to Boise in 2016 and regularly travels by foot, by bike or by bus.
Kostelec has worked with 13 state departments of transportation and federal government agencies, more than 15 metropolitan planning organizations, and numerous municipal governments. He has led more than 50 pedestrian, bicycle and greenways planning and design projects for places large and small.