The Optare Solo is a low-floor minibus/midibus with one or two doors manufactured by Optare in the United Kingdom since 1998. The Solo name is a play on its low-floor status, the manufacturer marketing its vehicle as having an entrance that is "so low" from the floor, namely with kneeling suspension. In January 2012 Optare announced the end of production for the original Solo design with a modified Solo SR taking over. The original innovative design, featuring a front axle ahead of the entrance door, gained a Millennium product award, along with a Queen's Award for Enterprise. 3,857 original model Solos were built between 1998 and 2012. As of April 2017, almost 1,500 Solo SRs had been built. Construction The Solo is an integral midibus (as opposed to a separate chassis and body) built in a modular design, with steel frame and GRP panels. Detailed analysis and computer modelling of the design and any impacts of stresses it would see in service were undertaken by finite element analysis firm Analysis by Firth, based in Wigan, UK. It is powered by a Mercedes-Benz OM904LA engine, which produces or according to specification, and it is typically mated to an Allison 2000 automatic gearbox. Later, the options of a Cummins ISBe 6-cylinder engine or a MAN engine became available. There was also the option of a 4-speed Allison AT545 gearbox. In 2005 a hybrid Solo was constructed, using a small diesel unit and an Eneco (now known as Traction Technology) battery propulsion unit. The Optare Solo is available in various lengths: , , and - all wide. The chassis type code of the Solo denotes the length – M780 corresponds to 7.8m, M850 to 8.5m, and so forth. However, the Cummins-powered Solos required extra rear bodywork in order to accommodate the larger engine, which increased the overall length by . This is reflected in the chassis code, so a Cummins-powered Solo was coded M810, M880, M950 or M1020. Along with the launch of the model, the Solo was also first offered with LED-type rear lights, as opposed to the standard rectangular clusters. Seating capacities range from 25 for an M780, 29 for an M850, 33 for M920 and 37 for an M990. Original Variants Slimline A narrow-bodied version named the "Slimline" was launched in 2004 with the first examples entering service in August. It is wide, and identifiable by small wheelarch extensions mounted