Answer: Preventive patrol.
Explanation: Preventive patrol is the patrolling activity/service done by police team in a manner that any expected crime or misconduct cannot take place. Increment of the police members in particular area is seen during this patrolling so that chances of misconduct is reduced.
In the mentioned situation, the police officers are using preventive patrolling method by walking and driving though streets so that any sort of wrongdoing act should not happen. By being present in that area , police department is assuring the safety of public.