The contemporary heavy duty vehicle market, whether commercial or military, demands a power-plant that meets performance goals of power density and fuel economy, is cost effective, and has uncompromising reliability. Gas turbine engines have demonstrated these qualities in aircraft propulsion. When applying these same criteria for vehicular propulsion, gas turbines have been deemed uncompetitive due to high fuel consumption and diminished performance at part load, and high acquisition cost. Therefore, the challenge remained to design a gas turbine engine that incorporates all the advantages demonstrated in the aircraft industry (i.e., high reliability), but significantly lower the costs, and give the engine good part load fuel economy. This paper describes the studies and tradeoffs made in the design of a gas turbine engine, designated the GT601, which has demonstrated the ability to meet the vehicular propulsion system goals. Also documented is the more than 10,000 hours of test cell and vehicular experience, that demonstrates the reliability currently available for a vehicular gas turbine designed for the 1980's and beyond.