Police Methods | Section 4.2


Police Methods

Adam J. McKee, Ph.D.


Section 4.2: C.P.T.E.D.


Crime Prevention Through Environmental Design Guidebook

The basis of Crime Prevention Through Environmental Design (CPTED) is that proper design and effective use of the built environment can reduce the incidence and fear of crime. This in turn leads to improvements in the quality of life.

In contrast to the approach of addressing crime concerns by implementing visually affronting security or target hardening measures such as locks, hard barriers, security gates, security patrols, etc., CPTED promotes high quality and visually pleasing solutions as first responses that aim to enhance the legitimate use of space.

CPTED can be applied without interfering with the normal use of the space. It is easy to apply and can be economical to implement, especially if it is done early at the planning and design stages of a project.

The Four Principles of CPTED Are:  

  1. Natural surveillance  
  2. Natural access control  
  3. Territorial reinforcement  
  4. Maintenance and management

There are strong overlaps and synergies among the four CPTED principles. These have been identified separately for convenience and clarity of understanding. In practice, it may be useful to see all four principles as different facets of a single technique for dealing with the security of the physical environment. In respect to the first two principles, the term ‘natural’ refers to deriving surveillance and access control results as a byproduct of normal and routine use of the environment.

Natural Surveillance 

The fundamental premise is that criminals do not wish to be observed. Surveillance or the placing of legitimate ‘eyes on the street’ increases the perceived risk to offenders. This may also increase the actual risk to offenders if those observing are willing to act when potentially threatening situations develop. So the primary aim of surveillance is not to keep intruders out (although it may have that effect) but rather, to keep intruders under observation. Natural surveillance can be achieved by a number of techniques. The flow of activities can be channelled to put more people (observers) near a potential crime area. Windows, lighting and the removal of obstructions can be placed to improve sight lines from within buildings.

Natural Access Control 

Natural access control relies on doors, fences, shrubs, and other physical elements to keep unauthorised persons out of a particular place if they do not have a legitimate reason for being there. In its most elementary form, access control can be achieved in individual dwellings or commercial establishments by the use of adequate locks, doors and window barriers.

However, when one moves beyond private property to public or semi-public spaces, the application of access control needs more care. Properly located entrances, exits, fencing, landscaping and lighting can subtly direct both foot and vehicular traffic in ways that decreases criminal opportunities. Access control can be as simple as locating a front office to a warehouse.

While access control is more difficult on streets and areas that are entirely open to public use, there are other techniques for controlling access in these circumstances. For example, nonphysical or ‘psychological’ barriers can be used to achieve the objective of access control. These barriers may appear in the form of signs, paving textures, nature strips or anything that announces the integrity and uniqueness of an area. The idea behind a psychological barrier is that if a target seems strange, or difficult, it may also be unattractive to potential criminals.

Because any strategy that fosters access control is also likely to impede movement, careful consideration should be given to access control strategies. Such strategies may limit the opportunity for crimes, but should not hinder the mobility of potential victims.

Territorial Reinforcement 

People naturally protect a territory that they feel is their own, and have a certain respect for the territory of others. Clear boundaries between public and private areas achieved by using physical elements such as fences, pavement treatment, art, signs, good maintenance and landscaping are ways to express ownership. Identifying intruders is much easier in such well defined spaces. Territorial reinforcement can be seen to work when a space, by its clear legibility, transparency, and directness, discourages potential offenders because of users’ familiarity with each other and the surroundings.

Maintenance and Management 

This is related to the neighbourhood’s sense of ‘pride of place’ and territorial reinforcement. The more dilapidated an area, the more likely it is to attract unwanted activities. The maintenance and the ‘image’ of an area can have a major impact on whether it will become targeted.

Another extension of the concept is that territorial concern, social cohesion and a general sense of security can be reinforced through the development of the identity and image of a community. This approach can improve not only the image of the population has of itself, and its domain, but also the projection of that image to others.

With clear spatial definitions such as the subdivision of space into different degrees of public/ semi-public/ private areas and the raising of standards and expectations, the level of social estrangement would decline. This is known to be related to reduction in opportunities for aberrant or criminal behaviour, such as vandalism.

aintenance and management need to be considered at the design stage, as the selection of materials and finishes will impact on the types of maintenance regimes that can be sustained over time. For example, plant material should be selected for its size at maturity to avoid blocking of sight lines.

The “Three D” Approach

CPTED involves the design of the physical space in the context of the normal and expected use of that space by the users as well as the predictable behaviour of people around the space. CPTED emphasises the connection between the functional objectives of space utilisation and behaviour management. Conceptually, the four CPTED principles are applied through the 3-D approach, i.e. Designation, Definition and Design. The 3-D approach is a simple space assessment guide that helps the user in determining the appropriateness of how a space is designed and used. The 3-D concept is based on the three functions or dimensions of human space:

  • All human space has some designated purpose.  
  • All human space has social, cultural, legal or physical definitions that prescribe desired and acceptable behaviours.  
  • All human space is designed to support and control the desired behaviours.

By using the “Three D’s” as a guide, space may be evaluated by asking the following questions:

  1. DESIGNATION 
  • What is the designated purpose of this space?
  • For what purpose was it originally intended?
  • How well does the space support its current use or its intended use? 
  • Is there a conflict?
  1. DEFINITION
  • How is space defined?
  • Is it clear who owns it?
  • Where are its borders?
  • Are there social or cultural definitions that affect how space is used?
  • Are legal or administrative rules clearly set out and reinforced in policy?
  • Are there signs?
  • Is there conflict or confusion between purpose and definition?

For example, in a given space, certain behaviour or activities may be socially or culturally discouraged while others may be clearly prohibited by display of written instructions or rules. On the other hand, what is not acceptable in a certain space may be acceptable in others.

DESIGN

  • How well does the physical design support the intended function?
  • How well does the physical design support the desired or accepted behaviours?
  • Does the physical design conflict with or impede the productive use of the space or the proper functioning of the intended human activity?
  • Is there confusion or conflict in the manner in which physical design is intended to control behaviour?

Consideration of these questions may reveal areas that requires changes or improvements. For example, a space may need to have a designated purpose, it may need to be more clearly defined, or it has to be better designed to support the intended function. Once these questions have been considered, the information received may be used as a means of guiding decisions about the design or modification of the space so that the objectives of space utilization as well as natural surveillance, natural access control, territorial reinforcement and maintenance and management can be better achieved.

The four CPTED principles can be translated into various planning and design strategies that would enhance security. These strategies can be categorised as follows: 

  1. allow for clear sight lines, 
  2. provide adequate lighting, 
  3. minimise concealed and isolated routes, 
  4. avoid entrapment, 
  5. reduce isolation, 
  6. promote land use mix, 
  7. use of activity generators, 
  8. create a sense of ownership through maintenance and management, 
  9. provide signs and information and 
  10. improve overall design of the built environment.

The decision of which strategy or combination of strategies to apply will depend on the site condition, the functional requirements and the desired programming of the space, as well as the design intent.

✽✽✽

Sight Lines

Sight line is defined as the desired line of vision in terms of both breadth and depth. The inability to see what is ahead along a route due to sharp corners, walls, earth berms, fences, bushes or pillars can be serious impediments to the feeling of being safe. Large columns, tall fences, overgrown shrubbery and other barriers blocking sight lines adjacent to pedestrian paths could shield an attacker. Alternatively, low hedges or planters, small trees, wrought iron or chain-link fences, transparent reinforced glass, lawn or flower beds, benches allow users to see and be seen and usually discourage crime and vandalism.

  1. DESIGN VISIBILITY. Design visibility in the built environment means allowing for clear sight lines and avoiding isolated or hidden spaces. Recessed doorways can result in corners that are hidden from casual surveillance. Sharp “blind” corners create the same problem, especially on stairs or corridors where there may be no alternative routes of escape. Sudden changes of grade on walkways can also create “blind spots”. Certain improvements can be made. For example, columns and walls can be tucked into the built design as protrusions can hinder visibility. Visibility can also be improved through modification such as creation of windows and other openings in otherwise blank walls and removal of protrusions along walls. Improving visibility through such modifications will permit natural surveillance. Similarly, the location and design of fences, shrubbery and berms must also be carefully studied when design visibility is essential. In blind spots where no modification to the building is possible, the use of security mirrors or other security devices such as video cameras would be necessary even though these are not optimal solutions.

 

  1. PROBLEMATIC SPACES. Visibility should especially be taken into account when designing or planning spaces where risk to personal safety is perceived to be high, such as stairwells in multi-storey car parks, underpasses and lobby entrances to high-rise buildings.

 

  1. FUTURE SIGHT LINE IMPEDIMENTS. As the landscape matures over time, unintended screens, barriers or hiding places could be created. Therefore, planting in a landscape must take into consideration the growth, final height and habit of the plants. Plantings are best made with due consideration to the resources to be committed to their maintenance so as to ensure that the original sight lines designed do not get obscured over time. 

Lighting

Sufficient lighting is necessary for people to see and be seen. From a security point of view, lighting that is strategically placed can have a substantial impact on reducing the fear of crime. A basic level of lighting should allow the identification of a face from a distance of about 10 metres for a person with normal vision.

  1. MINIMUM STANDARDS. If the area is intended for nighttime use, lighting should provide adequate visibility. Pedestrian walkways, back lanes and access routes open to public spaces should be lit so that a person with normal vision is able to identify a face from a distance of about 10 metres. Inset spaces, signs, entrances and exits should be adequately lit. On the other hand, lighting of different wattage, colour temperature and rendition may also be used to make certain public areas “less hospitable” to gathering for long periods.

 

  1. PATHS NOT INTENDED FOR NIGHTTIME USE. Lighting is not desirable in an isolated area or for a path leading to some obscure places. Lighting such areas may provide a false sense of confidence for people during nighttime use. The paths or spaces not intended for nighttime use could be fenced off and remained unlit to avoid giving a false sense of security or impression of being used.

 

  1. CONSISTENCY OF LIGHTING. Lighting should be uniformly spread to reduce contrast between shadows and illuminated areas. More fixtures with lower wattage rather than fewer fixtures with higher wattage help reduce deep shadows and avoid excessive glare. 

 

  1. DESIGNING FOR NIGHTTIME USE. Design proposals should take into account the night time use of the outdoor spaces and specify the type, placement and intensity of lighting.

 

  1. PROTECTION OF LIGHTING. Light fixtures should be protected against casual vandalism by means of vandal resistant materials and design.

 

  1. 6PLACEMENT OF LIGHTING. Lighting should also be directed on roadside pavement and possible entrapment spaces other than on roads. Lighting should take into account vegetation, such as mature trees, and other obstructions that would cause light to be blocked off.

 

  1. 7. BUILDING MATERIALS. Light colour finishes on walls and ceilings should be used for places such as car parks and isolated routes leading to it. This may be preferred to using lights of higher intensity that consume more energy and are costlier to maintain.

 

  1. 8. MAINTENANCE. Lighting requires maintenance to preserve visibility. Bushes and trees that block off light should be trimmed. Lighting fixtures should be located at suitable heights for easy maintenance and replacement. Light fixtures should be maintained in a clean condition and promptly replaced if burnt or broken. Posting information indicating who to call in case of burnout or vandalised lights is desirable.

Concealed or Isolated Routes 

Concealed or isolated routes are often predictable routes that do not offer alternative for pedestrians. An attacker can predict where pedestrians will end up once they are on the path. Examples are underpasses, pedestrian overhead bridges, escalators and staircases. Predictable routes are of particular concern when they are isolated or when they terminate in entrapment areas.

  1. VISIBILITY OF CONCEALED OR ISOLATED ROUTES. If there is a need for the concealed or isolated route, it should be designed to incorporate visibility. If there is an existing concealed or isolated route and security is in question, it should be modified or eliminated. Concealed or isolated routes can be made safer by bringing in more activities, ensuring clear sight lines, improving lighting, installing emergency telephones and electronic surveillance devices.

 

  1. LOCATION OF CONCEALED OR ISOLATED ROUTES NEAR ENTRAPMENT AREAS. If there is an entrapment area or isolated area within 50 to 100 metres of the end of a concealed or isolated route, it should be modified or eliminated. An entrapment area located near a concealed or isolated route such as a tunnel or an isolated path provides the attacker with an opportunity to take a victim to a nearby entrapment area where a more serious crime could be committed.

 

  1. NATURAL SURVEILLANCE. Natural surveillance of a concealed or isolated route should be encouraged. A stair or a ramp may be located such that it has external glazed/ open areas and has a view from the surrounding properties.

 

  1. SIGHT LINES. If a pedestrian cannot see what is on or at the end of a concealed or predictable route, the visibility should be improved by lighting and/ or the use of a reflective surface such as mirror. 

 

  1. LIGHTING. Concealed or isolated routes should be adequately and uniformly lit. Lighting should be vandal proof and properly located. Light coloured walls and ceiling materials help to reflect light and can enhance the brightness of an area. Natural lighting is preferred and should be encouraged.

 

  1. SURVEILLANCE THROUGH HARDWARE. If a concealed or isolated route is enclosed and prone to crime e.g. passageway or stairwell, surveillance through security hardware should be considered and these hardware should be properly monitored.

 

  1. ACCESS TO HELP. Emergency telephones, intercoms, security alarms should be installed to concealed or isolated routes to allow users to summon help in emergency.

 

  1. ALTERNATIVE ROUTE SIGN. Signs should be placed at the entrance to indicate alternative well-lit and/ or frequently travelled routes. Certain pedestrian walkways, in the city for example, may be preferable during daytime hours only. As such, an alternate route should be indicated for evenings and weekends at the entrance.

Entrapment Areas 

Entrapment areas are small, confined areas near or adjacent to well-travelled routes that are shielded on three sides by some barriers, such as walls or bushes. Examples are lifts, tunnels or bridges, enclosed and isolated stairwells, dark recessed entrances that may be locked at night, gaps in tall vegetation, a vacant site closed from three side by barriers, narrow deep recessed area for fire escape, grade-separated driveways or loading/ unloading areas off a pedestrian route. Parking lots, petrol kiosks and school buildings isolated by school yards can also become entrapment areas, especially when there is less activity after operating hours.

  1. ELIMINATION OF ENTRAPMENT AREA. If there is an entrapment area, such as a hidden area below or above ground, a private dead alley, a walled area or a storage area adjacent to a main pedestrian route, it should be eliminated.

 

  1. CLOSING OF ENTRAPMENT AREA AFTER OPERATING HOURS. If elimination of an entrapment area is not possible, it should be locked or closed after operating hours. For instance, a passageway connection to a locked building should be locked as well.

 

  1. VISIBILITY. It is preferable to have natural surveillance. However, if an entrapment area is unavoidable, the area should be well lit with some form of formal surveillance. In the case of lifts, incorporation of glass windows in the design of lift doors would be helpful.

 

  1. ESCAPE ROUTE AND HELP. Design should provide for an opportunity to escape and find help. For example, fenced parking areas can have more than one pedestrian exit points. Deep recessed fire escape could act as an entrapment area despite being lit and thus it should be avoided.

Isolation 

Most people feel insecure in isolated areas especially if people judge that signs of distress or yelling will not be seen or heard. People may shy away from isolated areas and in turn such places could be perceived to be even more unsafe. Natural surveillance from adjoining commercial and residential buildings helps mitigate the sense of isolation, as does planning or programming activities for a greater intensity and variety of use. Surveillance by the police and other security personnel to see all places at all times is not practical, nor economical. Some dangerous or isolated areas may need formal surveillance in the form of security hardware, i.e. audio and monitoring systems. Aside from its cost, the hardware must be watched efficiently and attentively by staff trained for emergencies.

 

  1. NATURAL SURVEILLANCE OF ISOLATED ROUTES AND PUBLIC SPACES. Natural surveillance of public spaces such as plazas, open green spaces, isolated pedestrian routes and car parks should be encouraged through planning and design. Blank facades or buildings set far back at street level should be avoided as they can create a sense of isolation.

 

  1. PROBLEMATIC ROUTES. Isolated routes to and from car parks should preferably be overlooked by surrounding buildings. In a low rise development, it is desirable to provide parking so that there is natural surveillance from the occupants of the buildings or surrounding areas.

 

  1. FORMAL SURVEILLANCE. Telephones, emergency telephones or panic alarms should be adequately indicated by signs. Video cameras and patrols could help monitor isolated areas.

 

  1. INCREASING ACTIVITIES. Compatible land use and activity generators create activities, thereby allowing visibility by users.

Land Use Mix 

A balanced land use mix is important for environmental, economic, aesthetic and safety reasons. Mixed uses must be compatible with one another and with what the community needs. For a residential development, a number of uses can be included by having a main street, a town square or park, prominent civic buildings and above all the ability of residents to walk to the place of work, to day care centres and to shops. The social value of frequenting local businesses provides a sense of security and safety as the local business people “watch” the street. Generally, any design concept that encourages a land use mix will provide more interaction and a safer place.

 

  1. COMPATIBLE MIXED USES Mixed uses should be compatible in order to encourage activity, natural surveillance and contact among people throughout the day. The first purpose in mixing uses should be to provide adequate and appropriate services to the primary users of an area. Examples include convenience retail shops, personal service shops and offices in primarily residential areas, especially if they provide local employment opportunities. Childcare centres, health and fitness clubs and grocery stores in office areas including the possibility of adding residential uses at a later date, are other examples of compatible mixed uses.

 

  1. BALANCING LAND USES Land uses such as pubs, clubs and bars are inevitable elements of urban life. However, they can be perceived as negative or undesirable depending on their locations in the neighbourhood. In order to minimise their impacts on the community, such uses should be balanced with positive measures by carefully selecting their locations in relation to surrounding uses.

Activity Generators 

Activity generators are uses or facilities that attract people, create activities and add life to the street or space and thus help reduce the opportunities for crime. Activity generators include everything from increasing recreational facilities in a park, to placing housing in the central business district or adding a restaurant to an office building. They can be provided on a small scale or be added as supporting land use, or intensifying a particular use.

 

  1. COMPLEMENTARY USES. Complementary uses should be introduced, to provide surveillance to potentially isolated areas, e.g. by locating administration office, lounge, TV room facing back lanes or side entrances.

 

  1. REINFORCING ACTIVITY GENERATORS. Activity generators should be located along an “active edge” or along one or two pedestrian paths in large parks or on the boundary of large developments. An “active edge” creates a boundary of space that is inviting rather than threatening to passersby. Appropriately licensed street vendors or food vendors should be encouraged in parks and the sensitive placement of seating areas informally generates activity along the edge of a path.

 

  1. DESIGN FOR PROGRAMMING ACTIVITY MIX. Park planning and design should provide opportunities for enhanced programming, such as cultural, recreational and community activities.

 

  1. GROUND-LEVEL ACTIVITY. Pedestrian oriented activities should be encouraged at ground level in high and medium density areas.  Increased density generally attracts more people and may create more anonymity and a sense of fear. This sense of fear can be mitigated by creating more ground level activities such as retail which could add “eyes” on the street.

Ownership, Maintenance, and Management 

Sense of ownership, or territoriality, is often considered a vital factor in making a place safer.  Taking responsibility and caring for an environment helps make it safer. If residents in a residential estate for instance, feel that the areas outside their doors do not belong to them, they will feel less safe, and will be less likely to intervene in a dangerous situation. Not knowing who has formal ownership contributes to insecurity since it is not clear who to report the problems to. On the other hand, measures taken to increase the sense of territoriality may sometimes increase opportunities for crime. The visual or real barriers separating many new housing developments from surrounding neighbourhoods may isolate residents from the wider community.

 

  1. TERRITORIAL REINFORCEMENT. The properties that are normally not protected and that can easily be intruded should be defined by the presence of design features and maintenance. For example, poorly defined front and rear yards could be defined by a small fence or by regular maintenance of the surrounding landscape.

 

  1. USE OF MATERIALS. Materials used for common facilities should be vandal resistant so that maintenance is minimal. Street furniture should be made of durable and vandal resistant materials.

 

  1. MAINTENANCE ENFORCEMENT. Properties should be well maintained to create a perception of ownership and safety. Building maintenance by law enforcement is a critical part of fostering a sense of ownership.

 

  1. REPORTING MAINTENANCE. Well displayed telephone numbers or web sites to call for repairs and report vandalism to properties, especially in public areas are desirable. For example, a broken lock, door or window or light could be reported.

 

  1. MAINTENANCE PRIORITIES. Offensive graffiti should be promptly removed either by the property manager or the public authority. Response to litter pickup and repairs should be prompt. A well maintained space gives an impression of ‘ownership’ and ‘care’.

 

  1. MANAGEMENT. Efficient programming and management of spaces, formal surveillance and good maintenance, for example by the management corporations of condominiums, and town councils taking care of public housing, can also enhance personal safety. If prompt attention is not given to maintaining a property, the result of lack of maintenance can contribute to a sense of fear.

Signs and Information 

Well designed, strategically located signs and maps contribute to a feeling of security. Signs should be standardised to give clear, consistent, concise and readable messages from the street. Having addresses lit up at night will make them even more visible. Where it is difficult to find one’s way around; signs with maps may help. Signs must be visible, easily understood and well maintained. Graffiti and other vandalism can make signs unreadable. If signs are in disrepair or vandalised, it gives an impression of lack of ownership and thus adds to a sense of fear.

 

  1. SIGN DESIGN. Signs should be large, legible and identifiable. The use of strong colours, standard symbols, simple shapes and graphics is recommended for signs of washrooms, telephones, information and help.

 

2 MESSAGE. Signs should convey the message with adequate information. For example, it should indicate where to go for assistance or help, or where the telephones and washrooms are, or the hours of operation of a underpass. The message should be conveyed in suitable language(s) or pictographs.

 

  1. SIGN LOCATION. Signs should be strategically located at entrances and near activity nodes (e.g., intersections of corridors or paths) and placed for visibility at an appropriate height.

 

  1. MAINTENANCE. Signs should be maintained on a regular basis to ensure that they are visible. This may involve trimming any landscaping growth or cleaning the sign. Clear signs in a car park help users to identify their location.

 

  1. MAPS. In large parks and buildings, maps or leaflets containing information appropriate to the different needs of various groups of users should be available.

 

  1. HOURS OF OPERATION. Where and when exits are closed should be indicated at the entrance of a route.

Overall Design 

The design and management of the environment influences human behaviour. A barren, sterile place surrounded with security hardware will reinforce a climate of fear, while a vibrant and beautiful place conveys confidence and care. Both the functional and aesthetic values of public and semi-public spaces contribute to a sense of safety. In particular, the degree to which users can find their way around influences the sense of security. Good design reinforces natural use of space and lessens the need to depend on signs in order to find one’s way around.

 

1 IMPORTANCE OF QUALITY AND BEAUTY. The design of the space, besides fulfilling functional objectives, should create an aesthetically pleasing environment that a person can enjoy. The security aspects should be considered as part and parcel of designing the space and fulfilling aesthetic values.

 

  1. DESIGN CLARITY. The design of the space should be easy to understand. The entrances and exits, the places to find people and the places to find services such as washrooms or telephones should be easy to find for a person visiting the place for the first time. The more complex a space, the more signs and other measures to improve accessibility need to be provided and this may lead to more confusion. An inviting environment creates an image that attracts people.

 

  1. AVOID UNUSABLE SPACES. The purpose for designing a space should be clear. Unused and unusable “dead spaces” should be avoided.

 

  1. NIGHT TIME USE. The design of the space should address night time use.

 

5 CONSTRUCTION MATERIALS. For better public safety and security, the design of the space should take into consideration appropriate materials, its placement, colour and texture to make the space inviting or uninviting. For example: bright and vibrant finishes create a sense of safety.

 


Source:   National Crime Prevention Council (NCPC) of Singapore.  Crime Prevention Through Environmental Design Guidebook.

http://www.popcenter.org/tools/cpted/PDFs/NCPC.pdf

 

Modification History

File Created:  08/10/2019

Last Modified:  08/10/2019

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This work is licensed under an Open Educational Resource-Quality Master Source (OER-QMS) License.

Open Education Resource--Quality Master Source License


 

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