crime prevention through environmental design

A Quick Review of

CPTED Strategies (Crime Prevention

Through Environmental

Design) By: Russell James, J.D., Ph.D., Asst. Professor, Dept. of Housing

& Consumer Economics, University of Georgia

The criminal’s SAT questions

Surveillance (Will I be seen?)

Access (Can I get in and out)?

Territoriality (Does anyone care what happens here?)

Surveillance (Will I be seen?)

Research

“burglarized houses had less visual access to immediately neighboring houses than did non-burglarized houses”

Brown, B. (University of Utah), Altman, B. (University of Utah). 1983. Territoriality, defensible space and residential burglary: an environmental analysis, Journal of Environmental Psychology, 3(3), 203-20.

“Convenience stores experienced mean annual robbery rate reductions after installation of CCTV systems (-23%); installation of video cameras with monitors (-54%)”

C. Casteel (UCLA) & C. Peek-Asa (UCLA). 2000. Effectiveness of crime prevention through environmental design (CPTED) in reducing robberies. American Journal of Preventative Medicine, 18, 99-115, p. 110

Office beverages available with payment on an “honor” system.Picture above payment instructions rotated weekly.Payments were higher when picture of eyes was posted.

M. Bateson, D. Nettle & G. Roberts (2006). Cues of being watched enhance cooperation in a real-world setting. Biology Letters 2, 412–414.

A B

Two groups with two computer backgrounds. Each person receives $10. Computer question: Do you want to share any of it with another (anonymous) participant?

K. J. Haley (UCLA), D.M.T. Fessler (UCLA). 2005. Nobody’s watching? Subtle cues affect generosity in an anonymous economic game. Evolution and Human Behavior, 26, 245–256

Shar-ing55%

Not Sharing45%

Normal Screen

Sharing88%

Not Sharing12%

Eyes Screen

K. J. Haley (UCLA), D.M.T. Fessler (UCLA). 2005. Nobody’s watching? Subtle cues affect generosity in an anonymous economic game. Evolution and Human Behavior, 26, 245–256

Access (Can I get in and out)?

Research

“Burglarized houses had fewer fences and locked gates surrounding the yard than did non-burglarized houses.”

Brown, B., Altman, B. (1983). Territoriality, defensible space and residential burglary: an environmental analysis, Journal of Environmental Psychology, 3(3), 203-20.

Preventing access by adding chain link fencing and lighting to lower levels of this parking garage led to 50% drop in reported crime.

Tseng, C.-H. (Ohio State U.), Duane, J. (Ohio State U.), & Hadipriono, F. (Ohio State U.). 2004. Performance of Campus Parking Garages in Preventing Crime. Journal of Performance of Constructed Facilities, 18(1), 21-28.

Territoriality

(Does anyone care what happens here?)

Research

“burglarized houses had fewer symbolic barriers characteristic of primary territories (i.e., fewer markers depicting the identity of the territory owners)”

Brown, B. (University of Utah), Altman, B. (University of Utah). 1983. Territoriality, defensible space and residential burglary: an environmental analysis, Journal of Environmental Psychology, 3(3), 203-20.

In a study of 400 convenience store robberies, one significant difference between robbed and non-robbed stores was distance from nearest graffiti

S. A. Hendricks, D. P. Landsittel, H. E. Amandus, J. Malcan, & J. Bell. (1999) A matched case-control study of convenience store robbery risk factors. Journal of Occupational and Environmental Medicine, 41(11), 995-1004

“Does it pass the SAT?”

Surveillance

(Will I be seen?)

Access

(Can I get in and out)?

Territoriality

(Does anyone care what happens here?)

Visual Examples

Will I be seen?

Surveillance: FAIL

Can I get in and out?

Access: FAIL

Does anyone care what happens here?

Territoriality: FAIL

Does anyone care what happens here?

Territoriality: FAIL

Can I get in and out?

Access: FAIL

Does anyone care what happens here?

Territoriality: FAIL

Access: Can I get in and out?

If no one cares what happens here, is it less risky to try opening the door with a crowbar or bolt cutter?

Territoriality impacts Access

Access barriers alone can be

overcome

Surveillance + Access +

Territoriality (SAT) work together

ACCESS: Does the fence make it harder to get in and out?

SURVEILLANCE: Does the fence make it less likely I will be seen when attempting to break in

through a back door?

Surveillance + Access + Territoriality may impact each other.

Does anyone care what happens here?

The fence says “Maybe”. Everything else says “No”

Does anyone care what happens here?

TERRITORIALITY: High level maintenance. Defined borders.

Short decorative fencing can enhance territoriality inside the fence without disconnecting from the surrounding neighborhood

Short decorative fencing can enhance territoriality inside the fence without disconnecting from the surrounding neighborhood

Short fencing, even if solid,

creates no surveillance problems.

As fences get higher, the access barrier increases, but the risk of visually disconnecting

from the neighborhood also grows

Does anyone care what happens here INSIDE the fence?

Does anyone care what happens here OUTSIDE the fence?

High fences may diminish territoriality outside the fence

High solid fences

• Indicates lack of territoriality outside of walls

• Reduces natural surveillance

Can anyone see what happens outside the fence?

High solid fences

• Indicates lack of territoriality outside of walls

• Reduces natural surveillance

Does anyone care what happens outside the fence?

High solid fences

• Indicates lack of territoriality outside of walls

• Reduces natural surveillance

High solid fences may create spaces with little surveillance or territoriality

Some high fences control access, but fail the S.A.T. by (1) Blocking

surveillance(2) Sending a clear

message that the area is dangerous, crime is accepted, and no one cares what happens outside the wall

Making the chain link fence opaque blocks surveillance and permits graffiti showing a lack of external territoriality.

With proper design and maintenance,

high fences can limit access without

damaging surveillance or

territoriality

A high fence blocking access without damaging surveillance or territoriality

Spikes can add a visceral element of access reduction that is still decorative and residential

Of course, you can go too far with anything!

Window bars limit access, but may also send a negative territoriality message about

neighborhood safety.

Glass block can create security similar to window bars but without the stigma

Most burglary entries do not occur through the front door, often because of natural surveillance.

Open access to side or rear entry points where there is no natural surveillance make for more attractive burglary entrances.

Access barriers to side or rear entrance can reduce the risk

A very short barrier may provide insufficient access control

As barriers rise, access is reduced

Tall opaque barriers limit access, but may also eliminate natural surveillance

The line of sight for entry points is critical.

Am I visible to outsiders here?

Am I visible to outsiders here?

Am I visible to outsiders here?

Am I visible to outsiders here?

Consider the sight-lines in this aerial shot of a new group of duplexes

Rear Entrance / Windows

Front Entrance / Windows

Side Windows

What are the sight lines for the potential entry points in this unit?

10 residences have sight

lines to the rear

entry

What are the sight lines for the potential entry points in this unit?

16 residences have sight lines to the front entry

What are the sight lines for the potential entry points in this unit?

11 residences have sight

lines to side

window

What are the sight lines for the potential entry points in this unit?

Rear Entrance / Windows

Front Entrance / Windows

Side Entrance/ Windows

What are the sight lines for the potential entry points in this unit?

2residences have sight

lines to rear

entrance

What are the sight lines for the potential entry points in this unit?

0residences have sight

lines to side

window

What are the sight lines for the potential entry points in this unit?

Zone outside residence

where sight lines are

covered by wooded area with link to walking trail

What are the sight lines for the potential entry points in this unit?

Which residence has better SAT scores?

What natural surveillance issue best predicted convenience store robberies?

C. Casteel (UCLA) & C. Peek-Asa (UCLA). 2000. Effectiveness of crime prevention through environmental design (CPTED) in reducing robberies. American Journal of Preventative Medicine, 18, 99-115, p. 110

Visibility from outside the store to inside the store was the most important sight line

C. Casteel (UCLA) & C. Peek-Asa (UCLA). 2000. Effectiveness of crime prevention through environmental design (CPTED) in reducing robberies. American Journal of Preventative Medicine, 18, 99-115, p. 110

Visibility from outside the store to inside the store was a more significant predictor of convenience store robberies than the number of clerks or the proximity to drug traffic, gangs, or subsidized housing.

C. Casteel (UCLA) & C. Peek-Asa (UCLA). 2000. Effectiveness of crime prevention through environmental design (CPTED) in reducing robberies. American Journal of Preventative Medicine, 18, 99-115, p. 110

At night, surveillance depends on lighting.

Of course, surveillance can be blocked by both darkness and solid barriers.

• line of site; access out

Lighting alone may not overcome natural barriers to surveillance

Lighting can also be important during the day, especially where lines of sight are limited

Neighborhood watch signs may

improve territoriality by indicating that

people care what happens in

the area

Of course, if no one really cares about the area, then there is no real community

ownership or territoriality,

and a sign may not have the

desired effect!

Territoriality fails when it appears that

no one is maintaining

an area. No one

is claiming ownership.

In short, no one cares what

happens there.

What signals do you get that territoriality

appears weak here?

Closed stairwells have low natural surveillance and easy access for both entry and escape

Combined with territoriality deficiencies, stairwells can create CPTED problem areas.

Design solutions can improve the

natural surveillance for

stairwells

Open stairwells have strong

natural surveillance properties

All ranges of natural

surveillance levels are

possible for stairwells

depending upon the design

solution chosen

“replacing bathroom entrance doors with right-angle entrances permit the warning sounds of crime to travel more freely and reduce the sense of isolation”

Sommer, R. (1983). Social design: Creating buildings with people in mind. Englewood Cliffs, NJ: Prentice-Hall

Auditory Surveillance

Cul-de-sacs may limit access, making visiting cars more noticeable

Cul-de-sacs make automobile escape more problematic as there is only one exit route

Street closures can provide similar access results

Pedestrian traffic can also be limited with street closures

High rise buildings provide weaker surveillance of

street level activity because of structural

separation, distance separation, and

sound separation.

This separation also limits the sense of territoriality over

street level activities.

Mid rise balconies create stronger surveillance and territoriality, connecting residents with street level.

Mid-rise balcony neighborhoods

create safer street level areas with high levels

of perceived surveillance and

perceived territoriality

Presentation by Russell James III, J.D., Ph.D., Asst. Professor, Dept. of Housing & Consumer Economics, University of Georgia.

Dr. James’ research has been published in a variety of housing and design related academic journals including: Environment & Behavior; Housing Policy Debate; Journal of Urban Planning & Development (ASCE); Journal of Performance of Constructed Facilities (ASCE); Housing, Theory, and Society; Housing & Society; Journal of the Community Development Society Please feel free to use any of these slides for any non-commercial purposes.

All pictures used in this presentation are creative commons licensed, have been purchased with rights to allow this usage, are from MS PowerPoint or are the author’s own photographs. Citations for all creative commons licensed photos are in the notes to each slide.