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Streets Are Catalysts For Lively and Safe Urban Spaces

Future Forum's junior research fellows, Norak Prak and Aronsakda Ses was published in Kiripost on July 18, 2023. Check out the original article here, and read it below!


Future Forum fellows, Prak Norak and Ses Aronsakda explore ways to create lively and safe streets in the Cambodian capital of Phnom Penh.

Traffic on Monivong Bridge in Phnom Penh. Kiripost/Siv Channa

We have probably all experienced this sensation: When you’re walking down a city street you can often innately sense whether the environment around you is inviting, comfortable, and safe—or not. And often it can be difficult to articulate why certain parts of a city feel this way, and others do not.

Many of these unconscious feelings are actually the result of the built environment around us. Intentional, or unintentional, decisions that designers and architects make can determine whether a space inspires feelings of warmth and safety, or whether the built environment triggers internal alarm bells for passersby.

The fact that the architecture of the built environment has the potential to affect the mood or perceived comfort of the user, is not a new concept. Designers often use this information to their advantage when creating or building private spaces.

Yet when it comes to public spaces in Phnom Penh the same level of attention and intentionality is often lacking, particularly when it comes to buildings that flank our city streets. As Phnom Penh continues to change and grow, the people responsible for the look - and therefore the feel - of the city must consider the impacts their work can have.

To boost feelings of safety and comfort in our public spaces, city planning authorities should formalize a few key design strategies that can have a major impact on the way public spaces are perceived. Codifying these strategies - namely street-to-building ratio, active facades and building gap ratio - into existing building regulations can ensure that new developments and existing urban areas encourage active, positive engagement between people and the streets and buildings they interact with.

Influencing behavior through architecture

User perception of safety along public streets is strongly linked to how lively a street is. Liveliness and on-street activity creates safer streets overall. Think about how differently you might feel walking along a street that is bustling, with pedestrians, with people dining at sidewalk tables, with kids biking along the road. Now think about how you might feel if you turned a corner and discovered your route takes you down a dark, empty street, bordered by high walls and closed gates. You might think twice about continuing on.

Fountain Dragons, Phnom Penh. Kiripost/Siv Channa

On-street activities are critical in that they attract users who provide eyes monitoring the street, thus creating a network of natural surveillance. This network, in turn, creates a safe street boosting the well-being of the neighborhood. People play an important role in making a street safe, but the design choices we make about the built environment greatly influence this dynamic as well.

One of the ways we can influence this dynamic is by creating active facades. This is a design term that refers to openings - windows and doorways - on the street-facing sides of buildings at the ground level that generate activity and interest. The degree to which a given building is open to the street determines whether and how people on the street can engage with a building. This could mean window shopping, stopping to read interior or exterior signage like menus, conversing with locals, and more. Active facade design features also crucially determine how easily the people within a building can observe or even engage with what’s happening at the street level.

This type of engagement, between streets and buildings and vice versa can make a huge difference in terms of perception of safety for residents and for visitors.

Sense of scale is another design decision that can affect how at ease a person feels while walking along a street. Sense of scale in a city is often measured using the street-to-building ratio, which refers to the width of the street in comparison to the height of the buildings that flank it. An ideal street-to-building ratio creates human-scaled spaces, provides shading, and creates a comfortable sense of enclosure and protection. When the street-to-building ratio is proportional, people feel more comfortable and secure.

But the opposite can also be true. A street that is too wide with short buildings lacks shading, induces a sense of desolateness, and creates too much distance between points of interest that makes the street more difficult to traverse.

The building gap ratio is the third design decision that can impact how a public space feels. This measurement refers to the size of gaps between buildings lining the street. The gaps guarantee adequate air circulation and natural lighting for the street. The more generous the gap percentage, the more natural air and light can get through.

Safety and comfort along public streets are mainly influenced by these three characteristics. Thus, having an active facade, comfortable street to building ratio, and facade breakage are crucial for a neighborhood to feel safe and therefore improve livability.

Phnom Penh, December 9, 2022. Kiripost/Siv Channa

Engaging Phnom Penh Streets

Phnom Penh does have a few prominent examples of streets whose design features lend themselves to an innate sense of public safety and comfort. One example of a particularly well-designed active facades in Phnom Penh can be found on street 308, also known as Bassac Lane. The liveliness and activity of this street is due in large part to the design characteristics of the local shops, bars and restaurants that line the street. These facades have been built with large windows, openings, awnings, and porches that allow, and encourage, pedestrians and building occupants to interact. The inclusion of signage, and decoration at eye level also encourages street users to engage with these spaces, helping to maintain an active connection between the street and its buildings.

Bassac Lane is also a great example of a successful street-to-building ratio. The building height along these blocks is about 2 times the width of the street. This is a proportional arrangement for a pedestrian-oriented street where it is not too wide and buildings are not too short or too tall. With this kind of ratio, buildings are able to provide shading and a comfortable sense of enclosure to users without overpowering the human-scale feeling of the street below.

Some of these aspects are already present in many other streets in Phnom Penh. Yet the city would do well to re-examine these design concepts and to formalize them into existing building regulations, to ensure that our urban spaces can harness the safety advantages offered.

Bassac Lane off Street 308. Kiripost/Siv Channa

Policies to ensure safe and comfortable streets

Cambodia’s existing building regulation, Sub-decree No.42, should be further elaborated upon with provisions for the design characteristics explained above.

First, an ideal active facade ratio - which denotes how much of a building’s facade is made up of windows and doors - should be regulated for all buildings. Preferably this ratio should reflect the type of street the building is located on.

For example, streets in residential areas should strive to reach an active facade ratio of 30%, meaning that about a third of the facade should consist of openings. For existing residential property, wall openings can consist of permeable material, enough to let air and light through but still respecting privacy. Air bricks and louver design - a staple of Khmer Modernist Architecture - can make a comeback serving this requirement.

Permeable fences also allow human voices to be heard by passersby. People may feel more at ease when hearing human voices as an ambient sound whether from the street itself or from within the fences.

Larger collector streets which tend to have numerous shops and businesses flanking them, should adjust the active facade to be made up of 50% openings, consisting of entranceways and large store windows. While on the busiest streets, like the boulevards which cut through city centers and dense neighborhoods, the ratio should be between 70% to 80% to accommodate the high concentration of shops, offices, and facilities along them.

Authorities should also consider setting a comfortable building-to-street ratio and building gap ratio. On residential streets, the building height should be 1 to 1.5 times the width of the street. Simultaneously, the gaps between houses should be maintained at 50%, meaning that a house with a street facing side of 6 meters long, the gaps of each side should be 3 meters long.

Collector streets should limit their building heights to 1 times the width of the street. And the building gap percentage should be 35%.

Active Street Policy

As for boulevards, where the density and scale of building would be much higher, building heights should be limited to 2 to 2.5 times the width of the boulevard. And retaining a building gap percentage of 5%.

On boulevards in the outskirts of Phnom Penh, where streets are too wide and buildings tend to be low and sparse, trees can be a very useful design element to take advantage of. Adding trees can add scale to an otherwise desolate space, as tree canopies help break up the space and create smaller, human-scaled areas within a larger plane. In addition, buildings can alleviate this issue by incorporating more decoration and detailing to help build a healthier sense of scale.

Of course exceptions should be made accordingly. Especially in areas like the central business district. In those cases taller buildings can be allowed, but compensated by setting the breakage between taller buildings to be higher.

In terms of the role of the street, American urbanist Jeff Speck famously described a user-friendly street as one where four things are happening simultaneously. A street is user-friendly when there is a reason to walk on the street (shops or destinations to walk to), when the street is safe and feels safe (safe from traffic and crime), when the street is interesting, and when the street is comfortable. If Phnom Penh were to formalize design decisions that lend themselves to these outcomes, the city can ensure our streets are safe, interesting, and comfortable for the city’s residents and visitors.



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