Urban Design for Architects

I've started a series unpacking how architects can better navigate the urban design process not from textbooks, but from experience. Here’s Part 1.

As our cities grow, designing streets that are safe, accessible, and comfortable for everyone has become more important than ever. Urban design is not just about buildings it’s also about how people move, interact, and feel in public spaces.

Smarter Streets with Curb Extensions

One small but powerful design tool that improves safety and walkability is the curb extension.

Curb extensions, also known as bulb-outs, are widened areas of the footpath at street corners or crossings. They reduce the crossing distance for pedestrians and improve visibility by pushing the sidewalk out past parked cars. This simple change can make a big difference in helping both drivers and pedestrians see each other more clearly, especially in busy or residential areas.

On the left side, the sidewalk ends before the parked cars. This creates a problem: drivers cannot easily see pedestrians waiting to cross because their view is blocked by parked vehicles. The sightlines are limited, shown here as a dark red triangle. A child or adult stepping out from behind a parked car can be completely hidden from an oncoming driver’s view. This kind of layout increases the risk of accidents, especially in busy urban areas where both foot traffic and parked vehicles are common.

Now, look at the right side of the image. The sidewalk curves outward into the parking lane. This simple change moves pedestrians further into the driver's line of sight, improving visibility for both. The green sightlines show how drivers can now clearly see someone standing at the edge of the crossing. At the same time, pedestrians also get a better view of approaching vehicles.

This small shift in curb design brings a big improvement in safety. It also makes crossing the street quicker and easier by shortening the distance between sidewalks.

In this illustration, You can see how the visibility around curved streets can either create a hazard or improve safety depending on the road design.

Let’s start with the top diagram. Here, a vehicle is approaching a curve, but a building or obstruction is located close to the road’s edge. The driver’s line of sight is blocked by this obstruction, which makes it difficult to see oncoming vehicles or pedestrians coming from the other side of the curve. This blind spot increases the chances of a collision, especially on narrow, fast-moving streets.

Now look at the bottom diagram. The same curve exists, but there’s a key difference the pavement has been widened on the inside of the bend. This small design intervention shifts the driver’s position outward, opening up the sightline around the obstruction. As a result, the driver has a clearer view of what's ahead, which allows for better reaction time and safer turns.

This is how modifying road geometry, even slightly, can solve real-world visibility problems. It’s a practical design move that not only makes driving safer but also improves the flow of movement around tight corners and dense built-up areas.

At the top, we see a straight crosswalk that leads directly across the road and the median in a straight line. At first glance, this may seem like the simplest solution. But this design has a hidden risk: pedestrians crossing the road tend to look straight ahead, not toward oncoming traffic. As a result, they might step into the street without noticing approaching vehicles from the left or right. In the image, a test setup using a plastic dummy simulates a dangerous outcome to demonstrate this flaw.

Now compare it to the bottom half of the image. Here, the crosswalk is angled so that pedestrians are gently turned toward oncoming traffic before they continue across. This subtle shift in direction naturally encourages people including those with mobility aids or children to look toward cars before stepping off the curb. It improves the viewing angle, creating a safer and more intuitive crossing experience.

Even minor tweaks in geometry and alignment can dramatically improve pedestrian safety especially in busy or high-speed urban environments.

Source: pinterest

When a car makes a turn, it doesn't follow a single circular path the front and rear wheels follow slightly different arcs. As shown in the image, a standard car turning in a circular motion creates two curves:

• The inner turning radius (measured from the inside front wheel)

• The outer turning radius (measured from the outside front wheel)

  
  

Here the inner radius is about 3.5 meters, and the outer radius is about 6.0 meters, which is typical for a standard passenger vehicle. The distance between these two paths is known as the track width (here, 2.5 meters), which reflects the car’s width and wheel positioning.

These measurements are important because they define how much space a vehicle needs to make a smooth turn. If a corner is too tight, drivers may have to slow down significantly, reverse, or swing wide often creating conflict with pedestrians or other vehicles.

Designing roads with the correct turning radii not only improves comfort for drivers but also enhances safety by preventing sharp, fast turns at pedestrian crossings or intersections.

In this Diagram , I have highlighted the importance of providing enough space for a car to turn smoothly, particularly on curved roads. It focuses on how a passenger car behaves while turning, and what happens when the design does not account for the full turning movement.

Let’s start with the top diagram, marked with a red cross. Here, the curve is too tight. The inner turning radius is just 3.5 meters, and the outer turning radius is 6.0 meters. While this may seem enough for a standard car, the design fails to consider the car’s overhang the portion of the vehicle that extends beyond the wheels. Because of this, the front or rear of the car may swing out and clip the curb or another object during the turn. This makes the movement unsafe and uncomfortable, especially in narrow urban areas.

Now, look at the bottom diagram, marked with a green check. This design provides a wider turning radius about 7.3 meters on the outer side and 4.3 meters on the inner side, allowing the vehicle to follow a natural arc. The full path of the inner and outer wheels has been considered, along with the overhang, making the turn smooth and safe.

It’s also important to note the track width of 2.5 meters and total road width of about 5.8 meters, which gives enough clearance for the car to move without hitting the edge or crossing over the lane.

In short, If we Compare both the diagrams ,it shows that considering wheel radius isn’t enough. Good street design must account for the entire vehicle envelope including overhangs, wheel tracks, and turning behavior to ensure safe and efficient movement, especially at intersections and narrow bends.

As we've seen throughout this guide, good urban design is about creating environments that are safe, thoughtful, and comfortable for the people who use them every day. Small changes in layout and geometry may seem subtle, but together, they help build a safer, more connected public environment.

As architects, urban designers, and planners, our responsibility is to prioritize human experience in our streets. That means designing with empathy, observation, and an understanding of how people move, pause, and interact in public space. Have you faced challenges designing within an urban context? Share below.

Thanks for reading!

Over 9,000 copies sold, get your e-book copy now!

Get your copy here