In April 2014, Arriva announced they have ordered 97 'Micro Hybrid' StreetLites, 70 of which are the Max (11.5m) variant with 27 others of an unspecified length.

From:- http://en.wikipedia.org/wiki/Wright_StreetLite

The basic Streetlite concept has been around for long enough for teething problems to have been identified and resolved. Are the current problems associated with the micro-hybrid system?