When not answering calls, the police are expected to be patrolling openly to deter wrongdoing. The police have traditionally approached policing in this way, and it is important to realise that most crime is reported by, and detected on the basis of information from, members of the public. The police are heavily dependent on public cooperation - it is far more important than any legal powers to detect crime. But it has been pointed out that the strategy, especially patrolling, is very inefficient - the police rarely bump into criminals who are on their way home from a burglary. The proactive approach involves building up pictures of threats to the peace and potential criminality through the targeting of potential criminals and the surveillance of them.
Intelligence is vital so that threats can be identified and appropriate counter-measures taken.
But this information may or may not come from the general public. The dangers with this form of policings are that it is secretive and so less accountable and that the targets will be selected out of prejudice. In reality, both forms of policing are practiced at the same time and there is a compromise between them. On the one hand, patrolling and reactive policing is felt to have limited impact against serious or professional crime which must be the target of proactive policing. On the other hand, public tranquility and reassurance are important goals which can be addressed by startegies such as visible patrols.