Wright SRM
| Years of manufacture | 2016 to present |
| Length | 10.6 or 11.3 metres |
| Width | 2520 millimetres |
The Wright SRM is a double deck transit bus built in the United Kingdom. The initials SRM may refer to "Short Routemaster" and internally by Wright as "Son of Routemaster". The bus is an evolution of the New Routemaster that was introduced in 2013. Transport for London approached various bus manufacturers to design a bus that built upon the design of the New Routemaster. Alexander Dennis's offering is the Enviro400H City.
While the New Routemaster is integrally constructed, the SRM is built on the Volvo B5LH chassis. The SRM also has two doors instead of three and one staircase instead of of two. The drivetrain of the B5LH is mounted on the open side, so this does not allow for a door at the very rear. The front roof section of the bus is also an additional structure rather than part of the overall structure.
The B5LH chassis has a five litre diesel engine connected to Volvo's Integrated Starter Alternator Motor (I-SAM) in a parallel hybrid layout. I-SAM has a permanent magnet motor that also functions as a generator and is integrated with Volvo's I-Shift transmission. With a more powerful motor, larger capacity batteries and conductive charging, it is possible for the bus to operate in full-electric mode for an extended period of time. Known as the B5LHC, this chassis option was launched at the 2016 Euro Bus Expo.
Much of the New Routemaster's aesthetic is carried over to the SRM. There is also a high degree of parts commonality between the two models. The most noticable deviation is the rear. The roofline is more squared to accomodate passenger headroom at the rear seats. The top deck has a rear window that wraps around the side, evoking the glazed staircase of the New Routemaster.