In 38 years as engineer-manager of the Wayne County Road Commission (1918-1956), Smith was the moving force behind development of the road system and major airport in Michigan's most populous county. He shunned the early concept of a basically farm-to-market county road system and concentrated on developing a network of urban and inter-urban highways designed to serve an increasingly auto-oriented society. His program for systematic right-of-way acquisition was a model for metropolitan areas. Smith was Michigan's first deputy state highway commissioner, serving from 1915-1918. He was president of the County Road Association of Michigan in 1948.