Restructuring a pattern language which supports time-triggered co-operative software architectures in resource-constrained embedded systems

A wheelchair carrying vehicle comprising a head rest assembly which comprises a head rest support frame which is rockable about a pivotal axis fixed with respect to the vehicle body structure and located adjacent the roof panel of the body structure and which is lengthwise extensible toward and collapsible away from the aforesaid axis, at least one head rest member supported on the head rest support frame, the support frame being rockable about the aforesaid axis between a position having the head rest member located close to the roof panel and a position having the head rest member positioned adjacent the head portion of an occupant of the wheelchair carrying vehicle, a lock-unlock unit comprising a lock control lever rockable about the aforesaid pivotal axis and securely connected to the head rest support frame, the lock-unlock unit being operable for having the lock control lever selectively locked to and unlocked from the vehicle body structure. The head rest assembly may be one of two head rest assemblies which further comprises a conventional head rest assembly which is positioned in front of or at the rear of the former head rest assembly.