Naked: Streets in the 21st Century | Nudge

When the streets aren’t shared.

In the episode “Shared” of this series I introduced the concept of Naked Streets, also known as Shared Streets or Shared Space. On these streets, cars share space with pedestrians and cyclists with an equal distribution of priority. A big part of what keeps these shared spaces safe is the use of Nudge Theory. When applying the principles of Nudge Theory, engineers and planners can elicit safe driving behaviors and speeds without surveillance, signs, or enforcement. Nudges work with natural human behavior to create streets that are safe for all users, but are also more human, civilized, and in many ways, efficient. This practice is rooted in behavioral science, cognition, and general psychology and has major implications on the way we will engineer streets in the future. Not only are Nudges an example of applying scientific research in psychology to engineering problems, but it also engages the exciting science of Complexity Theory. This field will only grow in popularity as our computational power is finally at a level to enable it’s application broadly to problems facing the modern world.

Complexity Theory: New Science with Better Results

A complex system as defined by Complexity Theory is a combination of simple, easily defined sub-systems combined to create something that’s larger than the sum of it’s parts. Simple systems combine to create a larger system that is of a higher dimension than the component systems. Think of chess, every piece has a set of possible, clear moves, this is a simple system. Even with all of these pieces making predictable moves on a small board, it’s impossible to predict what a game will look like at move 20. You can track all the moves in a game, but this won’t help you predict what the next game might look like. No one has “solved” chess due to this complexity. In another way complexity is trying to explain why a hurricane hit a certain place at a certain time. The sub-systems within the hurricane are all measurable and predictable, but their combination makes the larger system the opposite. The relationship between these simple processes becomes a dimension within itself, then you have secondary relationships and cascading effects. The hurricane is deterministic because it happens for easily defined reasons; working backwards from the hurricane scientists could explain why it happened when and where it did. At the end of this road however, defining how some complex relationships resulted in one hurricane cannot help predict another without expanding the analysis. Other combinations and permutations of these processes might generate the same outcome. There might be processes that weren’t present in this case, but that could equally contribute to forming this same hurricane. For this reason, we often estimate complex outcomes using statistical probabilities, which are a shortcut to the more exact science of working through the deterministic steps. Shortcuts to cut through complexity are often called heuristics.

Photo by Jezael Melgoza on Unsplash

Complexity Theory and Nudge Theory in Transportation

Complexity Theory defines some of the concepts that make Nudges work. When faced with complex situations, humans naturally try to slow things down to give their brains time to process what is happening. We have a number of natural heuristics to deal with complexity. Some of these heuristics manifest as biases, sometimes experience gives us a best guess, other times we think statistically, and in some cases we flip a coin. Narrowing roadways or introducing angle parking makes drivers engage these parts of our brains. A driver’s pupils dilate, their heart starts to pump slightly faster, and their brain starts to work harder as they perceive this slightly unpredictable situation. If the situation were predictable like so many of our roads are designed to be, the person would just move along mindlessly, dare I say, maybe even distracted. Adding complexity and risk to the situation draws higher levels of attention and engages a reflex to slow down so the driver has increased time to process the complexity. The narrower road or angle parking introduce more uncertainty and unpredictability to the roadway than a freeway with mile long sight lines. Nearly all drivers respond to this situation by driving more attentively and cautiously in order to preserve themselves and others. The situation on the road becomes less predictable and more complex; drivers become more alert. With more variables to monitor, it has been shown that human drivers will slow down. Autonomous Vehicles will likely also follow suit for the same reasons, even more consistently than humans. The overwhelming majority of people do not want to die, and most of us don’t want to be responsible for the death of others. When we feel risk, we instinctively take precautions.

For people who like technical words and concepts, we present: Entropy of Information. (Skip this if you’re easily bored.)

An Information Theory Perspective

Another way to look at the use of complexity in shared space design is from the perspective of Information Theory. In Information Theory, Information Entropy is defined simply as the “amount of information contained by an event.” The higher the uncertainty within an event, the higher the Information Entropy. For example, drivers slow down in the presence of angle parking because the event they see, angle parking, doesn’t tell them enough to know that a car won’t back out into their path from out of sight. On an empty road, it’s almost certain a car will not surprisingly back into the drivers path. Angle parking has a higher Information Entropy than the empty road. Another way to look at Information Entropy is as a measure of how likely outcomes are, given certain early observations. If you can’t predict the outcome of an event, then the early observations you’ve made have high Information Entropy. On the other hand, if a certain observation makes the outcome very predictable, the Entropy of Information is low. For instance, if you see many cars ahead of you and the traffic light ahead of them turns red, you can easily predict the outcome: cars ahead applying their brakes. That’s low Information Entropy. In another case, you might see many cars in front of you all take a corner you can’t see around; the Information Entropy is much higher. They could be stopped, the road could be washed out, there could be a traffic jam that starts right there, or it could be clear. It’s hard to say…

Nudges aren’t just about Speed Control

We used the example of traffic calming to illustrate Nudge Theory in action, but there are other applications of Nudge Theory in transportation engineering. In the case of shared streets, even when you take signs and grade separations (curbs) out, you can still implicitly suggest separations of spaces for pedestrians, cyclists, and automobiles where necessary. By simply designing with changes in textures, colors, decor, plants, or the like, you can imply separate spaces for different modes. This applies even if it’s completely allowable for them to take the same spaces. This can be used to make Naked Streets safer for vulnerable road users. Nudges on urban streets, particularly naked or shared streets, are anything that implicitly directs traffic using cutting edge behavioral and cognitive psychology. They can guide turning movements, manage speeds, or implicity manage right-of-way.

Our Current “Roads” Apply the Opposite Philosophy

I use the words “street” and “road” differently. A “street” is a focal point of a community, where neighbors interact, commerce takes place, events are hosted, and humans are the focus. Streets take people TO PLACES. Roads are designed to almost exclusively move cars, with minor provisions for other modes. Roads move drivers THROUGH places. Roads have invaded cities. In nearly all cases, this is for the worse. Road-thinking has dominated engineering and planning professions for decades. In some cases, this thinking has even shaped the way economists viewed cities. During the 20th Century and diminishingly into this Century, transportation engineers tried to remove complexity from roads. We tried to make things on roads predictable, extend sight lines, and severely limit human (pedestrian) movement, replacing it with something more robotic. In many ways, humans were given less choice and liberty was constrained. Perhaps worst of all we designed roads for higher speeds than we posted on the speed limit signs. All this in an effort to make roads “safer.” In the end, we ended up guaranteeing sub-optimal traffic law compliance and roads that can never result in zero fatalities as designed. In other words, these roads were built to fail. They relied on humans to manage their own human nature. In the future, we’ll work with human nature instead.

Coming Down Hard on 20th Century Engineering

Let me just keep ranting about 20th Century roads for a few more lines: In the 20th Century “roads” gave drivers too much safety. People will act riskier the safer they feel. It’s called Risk Compensation. Coincidentally, this link on Risk Compensation from Wikipedia brings up the Shared Streets we’re talking about. In the past, engineers took away as much driver choice as possible and made things feel extremely safe. They designed for idiots and that’s who ended up on the road, idiots. We all sort of become idiots on the road, don’t pretend you’re immune. Suddenly drivers must fight every urge to drive faster, closer, and riskier than what our driver training course taught us. These urges are natural, our bodies and minds FEEL safe and our intrinsic urgency tries to take the wheel. New research is showing that willpower is a depleting resource. Charles Duhigg covers this in his book, The Power of Habit, I highly recommend you check it out. People tired from work and busy lives exhibit less self-control. Engineers in the past asked drivers to use a scarce and therefore valuable resource to force themselves into unnatural behavior on our roadways. Sure, this can be a sacrifice we all make for the collective good, but wouldn’t it be better to make driving safe, efficient, AND enjoyable? Shouldn’t we aim for a society where liberty and freedom of choice are options even on our roadways? Shared Streets and Nudge Theory suggest using the human desire for self-preservation to manipulate their behavior on roads rather than using willpower to force conformity. Make people’s choices their own and you’ll see much greater compliance. This will make roads much safer.

Moving people, inside and out of cars. Photo by Francesco Tommasini on Unsplash

This works for AVs too.

Naked Streets and Shared Streets let pedestrians move freely. They will certainly act in a manner to keep themselves safe, making eye contact with each other and negotiating with one another. Naked Streets put decisions back in the hands of drivers, cyclists, and pedestrians. That’s why drivers will drive more slowly and pedestrians will take optimized paths.

With all that, any discussion about what to do with transportation in the future must include a discussion about AVs. Essentially, AVs give you two choices:

  1. You can double-down on 20th Century “roads” and further restrict human/pedestrian movements in cities; or
  2. You can return to the “streets” of every other century and make AVs and cars the visitors in these very human optimized spaces.

AVs will easily have the capabilities to navigate shared streets. Though it will look different than the vision of AVs driving around the city at 200 mph. Here’s a great article When Cyclists Oppose Bike Lanes that challenges concepts about who has priority in the public spaces within our cities.

That’s it for today, next we’ll get to the many examples of shared or semi-shared streets!