Target hardening increases the efforts that offenders must expend in the commission of a crime and is the most long-established and traditional approach to crime prevention. It is directed at denying or limiting access to a crime target through the use of physical barriers such as fences, gates, locks, electronic alarms and security patrols.
Excessive use of target hardening tactics, however, can create a 'fortress mentality' and imagery whereby residents withdraw behind physical barriers and the self-policing capacity of the built environment is damaged. This is, effectively working against CPTED strategies that rely on surveillance, territoriality and image. In addition it can reduce the benefits offered by positive image management.
The DesignOut Crime/CPTED components of surveillance, access control, territorial reinforcement, activity support, image/management, and target hardening have all individually contributed to reducing crime and the fear of crime in a broad range of studies.
By optimising opportunities for surveillance, clearly defining boundaries (and defining preferred use within such spaces) and creating and maintaining a positive 'image', urban design and management can discourage offending.
This is explained by the fact that offenders are potentially more visible to 'law-abiding' others, and therefore, perceive themselves to be more at risk of observation and subsequent apprehension.
Additionally, a well-maintained and appropriately used environment can signify that a sense of 'ownership' and proprietary concern exists within the community.
Some researchers (e.g., Fisher and Nasar, 1992) have introduced a threefold grouping of physical features; prospect (for the user), refuge (for the potential offender) and escape (for the user and potential offender) into CPTED theory. Taylor and Harrell (1996, p. 9) conclude;
Research confirms that fear [of crime] is higher in locations that offer good refuge for the potential offender but low prospect and escape for the user
Some have expanded on these ideas to consider social and demographic dimensions, since it is people who must 'self-police' within urban space. This may not always happen, however, even if the space is designed to encourage it.