These are part of a contract awarded to Optima Bus LLC in 2006 by the town of Avon, CO. The original award included a base order of up to five hybrid Opus buses with an option of an additional 10 buses.
The diesel hybrid system combines a Siemens ELFA electric drive system with a 6-cylinder, 5.9-liter Cummins ISB 260 hp (194 kW) engine, integrated and controlled by the ISE ThunderCan hybrid control system. Storage is provided by dual ISE/Maxwell ultracapacitor packs. Dual 85 kW electric drive motors provide 200 Nm of rated torque each.