2.23 The management teams of individual prisons, whether privately or publicly managed, are required to balance potentially competing priorities. The Prison Service's two key objectives are to hold prisoners in a safe, decent and healthy environment and to reduce crime by providing constructive regimes. There can be tensions between these objectives of security and rehabilitation. For example, rehabilitation involves ensuring that prisoners are engaged in purposeful activity (such as education or employment). However moving prisoners around the prison to such activities can increase the risk of assaults, drug dealing or escapes. Prisons are complex entities which suggests that any system which attempts to evaluate total performance needs to be sophisticated. Simply increasing the number of quantifiable measures does not necessarily aid in differentiating between the performance of different prisons. However, the Prison Service has recently developed two systematic approaches (a traffic light rating system and the weighted scorecard) which are potentially effective tools for analysing relative performance.