Dr. Stewart was a licensed Master Mariner and commanded ocean vessels. He managed a fleet of vessels valued at $500 million and has been a Wisconsin small business owner. He was a Captain in the U.S. Naval Reserve.

Dr. Stewart taught undergraduate and graduate courses at universities for over thirty years. He has been the Principal Investigator for over $11 million in transportation research grants. He has extensive publications and presentations. He is active in professional organizations and a member of several boards of directors.