12-h shifts are popular but are they a solution?

The effects of a trial change in police officers' shift schedules from 8 h (Control) to 12 h (Trial) shift rotas were studied at four sites (2 control/2 trial). Few differences were found between trial and control groups both at Time 1 and at Time 2 after a 6 month trial period. The change in duration of shifts was neither substantially detrimental nor beneficial in comparison to the original 8 h system. It was evident, however, that differences existed between the two trial 12 h system sites. Significant system by time interaction effects were observed for sleep, alertness, psychological health and satisfaction variables which appeared to be linked to the nature of the implementation of the 12 h rotas. Flexibility and the opportunity to have some control over working time appears to be a significant factor in the way a rota impacts upon the individual and its acceptance by a workforce.