Have you ever wondered why so many city benches are rigid, uncomfortable, and impossible to lie down on?

It's thanks to a controversial trend called "defensive design" — a strategy to prevent crime, loitering, and other urban issues — which includes those boxy benches with multiple armrests so people can't sleep on them.

"It targets people who use or rely on public space the most," says researcher and public space advocate Cara Chellew. "Especially people who are homeless, or youth."

Spikes on signs, metal studs on fountains and extra armrests are just a few examples of a controversial trend called "defensive design." 1:13

Chellew recently launched #defensiveTO, a volunteer-based online mapping project to document the use of defensive design in the Toronto area and beyond.

In little more than a week, she says, a couple dozen volunteers have shared more than 100 instances of what some dub "hostile" design elements.

And there's a broad range: many images show benches with multiple armrests and rigid backs.

Researcher Cara Chellew recently launched #defensiveTO, a volunteer-based online mapping project to document the use of defensive design in the Toronto area and beyond. 'It targets people who use or rely on public space the most,' she says. (Paul Borkwood/CBC News)

Others reveal the prevalence of metal studs along fountains, concrete barriers, and sidewalks, which stop skateboarders from grinding along the edges, spikes on storefront signs to prevent pigeons from landing, and carefully-placed planters to keep people from loitering or sleeping near shops or restaurants.

"In my opinion, it's a form of visual violence," Chellew says.

"It looks hostile, and unfortunately, I think it's a waste of resources when we're also trying to activate and make our public spaces more human-centred and lively."

Defensive design doesn't solve social issues, critics say

Others note while defensive strategies keep vulnerable and marginalized people out of public view, they don't solve the root causes of social issues.

"If we're looking for a solution to people experiencing homelessness, putting up a third railing on a bench so someone can't take a nap in a park isn't a solution to that problem," says Jake Tobin Garrett, manager of policy and planning at Canadian park advocacy organization Park People.

"It's a systemic issue of housing and income inequality."

These controversial 'anti-homeless' spikes were quickly removed after they were installed in front of a shop in downtown Montreal several years ago.

In Toronto, design trends targeting the homeless go hand-in-hand with city bylaws making it illegal to sleep or erect tents in certain spaces, notes long-time street nurse and housing advocate Cathy Crowe.

What's worse, she adds, is that the focus on these policies coincides with an ongoing housing and homelessness crisis that sees the city's shelters continually at or close to 100 per cent full.

"The shelter crowding is so severe that people are laying all over the place," she says.

Rafi Aaron, a spokesperson for the Interfaith Coalition to Fight Homelessness, believes cities like Toronto need to recognize homelessness is a year-round issue and find solutions beyond the warming centres that pop up each winter.

"This wouldn't be such a prevalent issue if we acknowledged and built things like social housing, transitional housing, and shelters," he says.

"Hostile architecture is so far down the chain of actual solutions."

Metal pieces along a concrete bench in Grange Park, which stop skateboarders from grinding along the surface, are just one example of defensive design in downtown Toronto. (Paul Borkwood/CBC News)

#defensiveTO project

Click around the #defensiveTO map, a project to document the use of defensive design in the Toronto area and beyond.

Controversial trend 'affects everyone'

Despite the criticism, defensive design isn't new.

"It's been in cities as long as we've had cities," Chellew says. "Walls have kept people out, guard towers protect the people inside."

The modern version is visible around the world, from major urban centres like Paris, Vancouver, Montreal, and New York, to smaller municipalities like Moncton, New Brunswick — where, five years ago, residents debated whether posts and fences were "anti-homeless design or hostile architecture," CBC News reported.

Moncton residents are debating some architectural design elements along city streets that are intended to be so uncomfortable that it discourages people from loitering or sleeping in the area. 2:13

Chellew also says this recent trend is different, and problematic, because most of the defensive elements are hidden within more socially-acceptable ones.

"It's meant to not be seen, but to be felt by the people who are targeted," she explains.

So is it time for cities to rethink this controversial design philosophy?

"We should absolutely be taking a hard look at how we're designing our public spaces, and if this is in line with a philosophy we tout about public spaces being open to everyone," Garrett says.

In Toronto, city officials approve designs for many parts of the public realm, with the goal of these spaces being inclusive to everyone.

But while critics have raised concerns about park spaces not hitting the bar, city planners are also taking into account durability and accessibility, according to a statement from Toronto's planning department provided to CBC Toronto.

In Berczy Park downtown, which is known for a fountain surrounded by dog statues, the city says protective studs were added "following an incident where a statue was extensively damaged by skateboarding and needed costly repairs."

And when it comes to park benches, "centre arms and bench backs are often used to create more accessible park seating," the statement reads.

In Montreal, changes are already happening. In 2014, the city's mayor took to social media to deem anti-loitering spikes unacceptable, CBC News reported at the time, which led to the removal of a set of spikes from one ledge along a downtown sidewalk.

The "problematic" trend limits the types of people who can use the public sphere, which is meant to be accessible to the entire population, Garrett adds.

"This is something that affects everyone," he says.

"When a public space is designed with extra railings and bars and spikes on things — it doesn't seem welcoming."