A System of Safe, Human-Centered Streets
Jon Larsen is a Strong Towns member and professional engineer. Today he's sharing a guest article proposing a new way to look at and design streets.
Earlier this year, I wrote an article calling out the traffic engineering profession’s epic failure to design streets that are safe for all users. At the heart of the issue is an unwillingness to acknowledge that we need to lower speeds to make our streets safe. I was nervous about how this critique would be received by my peers, but thrilled at the positive response and desire by many to fix this problem. I have had numerous conversations with fellow traffic and transportation engineers who are ready to make some changes, who are willing to do their part to make our streets safer. This article is a follow up, laying out a strategy for how to proceed in making more of our streets human scaled and safe.
Too many of our streets are designed in a way that sets people up for disaster, yet we blame the consequences on human error. In The Design of Everyday Things, Don Norman points out:
Human error usually is the result of poor design: it should be called system error… Pinning the blame on the person may be a comfortable way to proceed, but why was the system ever designed so that a single act by a single person could cause calamity?
Yes, human error is the cause of the majority of the crashes on our streets, but our design needs to be more forgiving of these errors. This means designing streets for slow speeds, because no design feature is more forgiving than slow speeds.
The Difference Between a Road and a Street
How do we get there? I believe that the core of the problem is the crossover of design standards between highways and streets, particularly the use of highway design standards on streets. The result is unsafe streets where high-speed traffic mixes with people walking or bicycling. Here are some ways that highways (also known as roads) and streets are different:
When we try to force streets to act like highways or highways to act like streets, we end up with an awkward compromise that leaves no one feeling satisfied or safe. The result is the infamous STROAD — part street, part road. Known as the “futon of transportation,” stroads are frustrating to motorists because the highway-like design tells you that you should be able to drive fast with no impedances, but instead you find yourself speeding up and stopping over and over again. Stroads are bad for business and the pedestrian environment because high speed traffic leaves little possibility of drivers seeing a local business and deciding to stop, and pedestrians feel unsafe with cars whipping past them. It turns out that streets and highways don’t play well together. Instead, you need to go all in on one or the other. Like Nassim Taleb’s barbell strategy, it sometimes works better to go for either extreme and avoid the messy middle.
With endless variations and sub-variations of street typologies available to us, we need to move past the limited “local, collector, arterial, freeway” hierarchy which is so prevalent in the traffic engineering world. This hierarchy only describes the traffic-carrying capacity of the highway or street, but tells us nothing of the bicycle, pedestrian, transit elements, urban design, or adjacent land use.
By developing specific names for the types of streets we want, we are better able to get the outcomes we are after. The important thing is to make an intentional choice about the feel and character you want for each community and carefully design the streets to support that vision. It’s unrealistic to expect every street to be highly walkable and charming. We need some areas to be industrial. Some streets are tasked with doing the dirty work of the city. That’s OK, but be intentional about it.
A side note about the relationship between speed and capacity on urban streets: There isn’t one. In traffic engineering terms, capacity is the number of vehicles per hour that a street can carry. On an urban street, capacity is determined almost entirely by how much traffic can get through the intersections, which is mostly influenced by how long through-traffic has to wait for side street and left turning traffic. For all practical purposes, speed is irrelevant when determining capacity. Whether people are traveling 40 mph or 20 mph, the same number of vehicles will get through. One scenario just happens to be considerably safer. On freeways and limited access highways, there’s a strong correlation between speed and capacity. But, as we’ve established, streets and highways are not the same thing.
Building Great Streets
Streets can make or break a city. I highly recommend the book Street Design by Victor Dover and John Massengale for in-depth analysis and inspiration on designing streets that are attractive and highly walkable. The NACTO Urban Street Design Guide is another fantastic reference. Great streets require thoughtful care for the way the buildings (private realm) and the street (public realm) interact with each other. Yes, streets carry traffic, but they do so much more. Great streets are human-scaled (not car-scaled) and serve as inclusive places where people gather for shopping, celebrations, community events, and chance encounters with new and old friends.
Great streets have a seemingly effortless interface between the public and private realm. They require careful design of the sidewalk, landscaping, bike lanes, and urban design elements. The buildings are thoughtfully constructed to work well with the streetscape and the public realm. More often than not, great streets are lined with trees between the sidewalk and the travel way.
My hope for the coming months and years is to see the growing “great streets” revolution take off, where engineers, planners, architects, developers, and residents work together to create streets that are beautiful and safe, designed around the needs of humans first.
Here's a 5 step process for fixing our streets so they are a safe, vibrant element of a Strong Town:
- Identify what you want each area of town to be. Zoning maps and land use plans are good places to start.
- Highlight and pay special attention to areas where you want or expect concentrations of people on foot, especially if these are vulnerable populations like children. Examples would be schools, parks, libraries, town centers and residential areas.
- Develop a robust set of street typologies, with a name for each street type. Naming something makes it real and has a powerful impact. Consider using a tool like streetplan.net, which is free and allows anyone to develop a conceptual street cross section and share it with others.
- Match streets with land uses. Identify what each street should be, not necessarily what it currently is. It’s OK to be aspirational.
- Go to work fixing your streets, one segment at a time.
Different Types of Streets
The following are some proposed street typologies which can be used as a starting point for your community. I also included some thoughts on compatible land uses for each street type. Notice the emphasis on designing for slow speeds, which is the most important element for safety.
Boulevard/Avenue
Designed to carry relatively high amounts of car traffic, but include investment in and care for the pedestrian realm. Sometimes boulevards have separated access lanes for turning, biking or reaching homes and businesses on the street.
Compatible Land Uses: Civic buildings, mixed-use office and retail, apartments, townhomes.
Main Street
Often one of the most charming streets in the city. Simple, human-scaled construction. Vehicular traffic is accommodated, but at a low speed. Buildings are 1-3 stories. Wide sidewalks filled with pedestrian amenities. Continuous wall of narrow buildings.
Compatible Land Uses: Shops, restaurants, apartments/condos, smaller office space.
Downtown Street
Fewer pedestrian amenities than Main Street, but still a “people first” street with slow traffic. Buildings are often 3+ stories.
Compatible Land Uses: Shops, restaurants, apartments/condos, smaller office space.
Neighborhood Street
Accommodates low volume two-way traffic at low speeds, but the primary focus is safety and comfort for walking and biking.
Compatible Land Uses: Residential: single family homes, corner stores, townhomes, duplexes, etc.
Yield Street/Woonerf
Streets so narrow that one car needs to pull over to allow opposing cars to pass. Very low speed, such that the line between the vehicle and pedestrian realm is blurred. Often, sidewalks aren’t needed.
Compatible Land Uses: Residential, shops, restaurants.
Promenade/Rambla
Wide center median, with or without a path or plaza down the middle. Low speed vehicular traffic is accommodated.
Compatible Land Uses: Shops, restaurants, wide variety of residential, office
Arterial Street
Carries relatively high amounts of car traffic. Minimal pedestrian accommodations. Side streets and access points are limited in an attempt to maximize traffic flow. Arterials often fall prey to becoming Stroads. (Consideration should be given to converting these to Boulevards.)
Compatible Land Uses: Big box and strip retail, drive-through restaurants, suburban office parks.
Industrial Street
Designed for semi-tractor trailers. Little or no pedestrian amenities. Wide turning radii. Buildings are pushed back from the street. There is a place for streets like this in most cities, but it needs to be an intentional choice.
Compatible Land Uses: Warehouses, manufacturing, etc.
Are there other street types that should be part of a strong town? Add them in the comments.
(Photo credit: First 4 photos by Jon Larsen, remaining photos from Google Earth)
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About the Author
Jon Larsen is a professional engineer in the state of Utah. He spent the first half of his career in the private sector as a traffic engineering consultant and currently works in the public sector doing travel demand forecasting. His specialties and interests lie in understanding the transportation/land use interaction, and in creating great places where communities can thrive. Jon is the chair of the board for the Congress for the New Urbanism (CNU) Utah Chapter. He has been a Strong Towns member since 2013.