The Hybrid Electric Transit Bus (HETB) was dubbed “Space Bus” by the technicians of the Cleveland Regional Transit Authority because of NASA involvement. Developed as a proof of concept test bed, the HETB has proven the use of ultra-capacitors as a viable energy storage device. In the process, a cost-effective engineered hybrid drive system was also developed. The HETB made its debut at the 1997 SAE Truck and Bus Conference in Cleveland. After the show, the HETB was prepared to complete the first round of proving ground testing under the scrutiny of NASA scientists. According to a NASA technical memorandum, published in January 1999, this series hybrid vehicle with ultra-capacitors produced 21.2% fuel savings for the “white book” central business district drive cycle over a traditional diesel powered vehicle.To prove the viability of the heavy series hybrid with ultra-capacitor storage, the team, lead by NASA scientists, elected to retrofit a veteran 40-foot Flxible transit coach rather than construct an optimized purpose built unit. This should provide transit authority operators a direct performance comparison of test results to their own on the road experience with similar units.This paper presents the performance, major component features, and implications for an engineered hybrid drive system derived from the Space Bus. This system can become a cost-effective alternative drive for medium and heavy hybrid vehicles. These would include, transit buses, school buses, delivery vans and similar vehicles used in frequent start/stop route service. The system as designed can also be supplied as a retrofit kit for converting existing transit buses to efficient hybrid power.