Keep potential intruders under observation. These points seem basic, and in effect they are. They see surveillance, access control and the resulting crime reduction as a by-product of the normal and routine use of the environment. The Three D's All this sounds quite vague, so let's get a bit more specific. To know which to use, you must first assess the physical environment you're looking to protect by running through the three D's.
All space has a Designated purpose.
It has social, cultural, legal or physical Definitions that suggest the desired and acceptable behaviours. And it's Designed to support and control those behaviours. These are some of the questions that follow the three D's. Clearly define the borders of the controlled space. Clearly mark the transitional zones that indicate movement from semi-public to private space.