Editor’s note: This is the fourth and final installment in a series on how trees and plants help to slow traffic, ameliorate climate change impacts and make growing cities more livable. Read Part 1, which describes the intellectual transformation that’s remaking streets and roads in Cascadia’s big cities, here. Read Part 2, which focuses on Vancouver and its green efforts in busier and denser areas, here. Read Part 3, which focuses on Portland and the strides the city has made with complete streets, here.

Seattle in many ways has been a North American leader in experimenting with concepts like adding nature to streets to make them better and safer for walking while collecting and treating stormwater. Recently, as the city grapples with some of the fastest growth among big US cities, many anxious Seattleites wonder: Can an Emerald City as famous for arduous process as it is for verdancy move fast enough to implement its best plans in the face of scorching rates of development?

The city was an early adopter of ideas around green and complete streets. In 2007 it became the first big city to adopt a complete streets ordinance, calling for all significant street maintenance and construction projects to also improve safety for people on foot and bike.

In the mid-2000s Seattle also was a pioneer in redesigning streets for managing stormwater with nature and safer walking, remaking a 12-block grid with new sidewalks, landscaping to “enhance the pedestrian experience in the neighborhood”, all while benefiting wildlife habitat and improving water quality.

Since the 1980s the city has designated a number of streets, primarily downtown, as “Green Streets” that are “designed to emphasize pedestrian amenities and landscaping in areas that have dense, residential land uses.”

In 2015, Seattle was among the first American cities to adopt Vision Zero, and created “a plan to end traffic deaths and serious injuries on city streets by 2030.”

Streets Illustrated paints a picture of future streets

Until relatively recently, though, Seattle continued to follow a blueprint for its streets that reflected its 1960s origins. That right-of-way improvements manual required wide lanes for safer vehicle travel at design speeds at odds with urban life, and it designated very little space for vegetation that could help to calm traffic and provide comfort and refuge for people on foot. It is a key reason why Seattleites still see so many scary car sewers in a city that aspires to be “the most walkable and accessible in the nation.”

The updated manual is critical because it sets street-development standards not only for public agencies but also for private developers—the people who are rapidly remaking the urban landscape.

In 2016 the Seattle Department of Transportation (SDOT) adopted an entirely new blueprint for its streetscapes in a design policy dubbed Streets Illustrated. The updated manual is critical because it sets street-development standards not only for public agencies but also for private developers—the people who are rapidly remaking the urban landscape.

Streets Illustrated breaks new ground among US cities in several ways. “In our old manual, we didn’t talk about space needs for complete streets, for transit, bikes, pedestrians or natural functions,” said Susan McLaughlin, urban design manager for SDOT. The manual establishes a dozen street types, each for specific purposes depending on the context, from downtown thoroughfares to urban village Main Streets to slow-traffic neighborhood streets. Almost all emphasize designs aimed at calming traffic and improving comfort and safety for people on foot, with street trees and vegetated landscape zones playing key roles. A citywide map designates which type of street belongs in each neighborhood, business district or urban village.

“Streets Illustrated was a huge move,” says Peg Staeheli, a Seattle-based landscape architect and principal with MIG | SVR who is a designer of complete and green streets. “I think that will be a giant step toward making our city greener. It says you shall have trees, have a pedestrian zone, address safe crossings.”