This paper gives the results of a feasibility study of an unusual three-wheeled commuter car. The study was one part of a General Motors program to build and evaluate a series of small special purpose cars for urban use.The 511 commuter car is intended for carrying two people from home to work at freeway speeds. Many radical design and construction features are employed. The car is small and lightweight, a combination which offers high fuel economy, low exhaust mass emissions, and some help for the parking problem.The 511 car, in its present form, is still a test vehicle. Although several major problems are unresolved, the car has demonstrated the technical feasibility of its basic concept.