Altering the Physical Environment There are three broad strategies for reducing crime opportunities through environmental design: defensible space, CPTED (Crime Prevention Through Environmental Design), and situational crime prevention. Defensible space uses techniques like territoriality and natural surveillance to increase feelings of ownership and control over private spaces. CPTED focuses on access control, surveillance, and territorial reinforcement. Situational crime prevention aims to reduce opportunities for specific crimes through 25 techniques that increase efforts, risks, and reduce rewards around criminal acts. All three strategies analyze crime problems and seek to limit crime opportunities through environmental modifications and place management.