How is public space designed to be defensive?
According to designers Selena Savic and Gordon Savicic, control is exerted through the use of "silent agents", design elements that manage the behaviour of people without the need for authorities to interact with citizens. Silent agents can take many forms, depending on the behaviour they are designed to restrict. Some examples are center bars on benches to keep people from lying down, metal protrusions on ledges to prevent skateboarding, surveillance cameras that keep a watchful eye on the city, and barriers that restrict access to space.
Defensive urban design often takes the form of:
These categories can be expanded by looking at the addition or removal of design elements or amenities.
The addition of center bars on benches, metal protrusions on ledges, and electronic deterrents like light, sound and surveillance, can make spaces uncomfortable or inconvenient to occupy. The removal of amenities like public washrooms, water fountains, and picnic tables, make public spaces inhospitable to occupy over long periods of time.
Defensive urban design can be further differentiated in accordance to the population targeted. The majority of forms target vulnerable groups-- people who are homeless or under-housed, people with mental health or addiction issues, skateboarders, and youth. Some forms do not discriminate against specific populations and are used to defend space against everyone.
This added complexity produces a variety a forms that does not fit neatly into bounded categories.