Cities have established parking regulations, often called off-street parking minimums, for each possible land use. When you build a new house or shop, or often when you simply remodel a building or change its use, you must provide a minimum number of off-street parking spaces. These regulations are meant to address demand for parking that cannot be met by nearby on-street spaces, but they have also led to increased development costs, less flexibility for adaptive reuse of existing buildings, and some pretty unattractive architecture.

This photo essay looks at some of the ugly architecture in Cascadia that has resulted from parking minimums. Many of the photos were sent in by readers who responded to our request for examples from their communities.

One obvious example is the ubiquitous seas of suburban parking. The commercial building pictured below is set so far back from the street, behind its legally required parking, that it’s hard to figure out what type of business operates there.

Photo sent by Derek Severson.

In Western Oregon, a mixed-use developed community called Fairview Village (below) has a Target store as its retail anchor. Although the development has won awards for livability and smart planning, this sea of required parking looks pretty standard.

Photo by Flickr user Brett VA.

The main entrance of this office building in McMinnville, Oregon, is barely visible from the sidewalk.

Photo sent by Derek Severson.

Offering a glimmer of hope in an oversized suburban parking lot, a Taco Time in Edmonds, Washington, has reclaimed a couple of parking stalls by creating an outdoor seating area for customers.

Photo sent by Brice Maryman.

Ugly parking areas are not unique to the suburbs, however. There are many urban examples as well.

Before parking minimums, buildings in Cascadia could be built to the property line because parking wasn’t a constraint. Now, developers must contend with building heights, setbacks for buildings, and parking regulations—all of which make it harder to develop affordable housing projects. This is especially true at medium densities and lower building heights because it’s harder to make parking garages or underground parking pencil for these smaller projects. This is easy to see by taking a quick look at a single street in Seattle’s Ballard neighborhood.

This classic apartment building in Ballard was built before parking minimums.

Photo by Jon Stahl, used with permission.

It sits just down the road from a cluster of “dingbat buildings”—apartment complexes supported on stilts with open carports on the ground level.

Photo by Jon Stahl.

In his book The High Cost of Free Parking, Donald Shoup describes how dingbat buildings proliferated in Los Angeles as a result of a 1930s zoning regulation requiring each unit of a multifamily dwelling to have one covered parking space.

Dingbat buildings are commonplace in Cascadian cities, too, such as this example in Seattle’s Ballard neighborhood.

Photo by Holy Outlaw.

And this one, also in Ballard.

Photo by Alan Durning.

And this one nearby.

Photo by Alan Durning.

And this dingbat fourplex, in Medford, Oregon.

Photo sent by Derek Severson.

These houses in South Seattle have covered garages instead of carports, but the dingbat form is much the same.

Photo by Alyse Nelson.

Parking regulations have not only given rise to architectural forms such as dingbats, but they have transformed existing types of housing, including the multifamily courtyard building. Courtyard housing was popular for decades before the advent of modern zoning codes. These buildings, such as the one pictured below in Portland, featured lovely green spaces surrounded by a U- or L-shaped structure.

Photo by Rex Burkholder, by permission, from Getting to 2100 blog.

This late-1920s courtyard building in Seattle’s Capitol Hill neighborhood features a landscaped green.

Photo by Meaghan Robbins.

Since the advent of parking minimums, courtyard-style apartments have continued to be built. But instead of landscaped courtyards, the buildings surround a different type of courtyard: a parking court, as illustrated by the Portland parking court below.

Photo by Rex Burkholder.

And these two parking courts in Seattle.

Photo by Alan Durning.

Photo by Alan Durning.

Where there could be a front yard, this motel-style apartment building in Seattle’s Ballard neighborhood has a parking court, too.

Photo by Alan Durning.

Parking minimums have also partly dictated the look of some of Seattle’s newer townhouses. Unlike more traditional row- or townhouse developments in other cities, which have a welcoming pedestrian entrance off the sidewalk, usually with stairs and a front porch or stoop, like these ones in Brooklyn…

Photo by rutlo.

…many of the new Seattle townhouses, like the two pictured below, feature dark parking courts and tall fences built to the sidewalk edge.

Photo by Flickr user jseattle.

Photo by Flickr user Holy Outlaw.

Blogger Gregory Wharton explored why the structures look like this. He found that strict zoning rules that set maximum building heights and setbacks and require an off-street parking stall for every unit have limited developers to a very specific design. As Seattle architect David Nieman has explained, the Seattle townhouse “is not a building type at all but, rather, a parking diagram that people happen to live above.” The resulting architecture has not been well received by the community, but, Wharton writes, “these projects are exactly what the Seattle zoning code tells developers to build.”

With parking rules essentially mandating their form, Seattle’s townhouses stand out as a perfect example of what’s known in the design community as “design by zoning.” Fortunately, the City of Seattle fixed this problem by removing parking requirements for multifamily housing in urban centers and villages in its recent multifamily zoning code update, no longer effectively mandating such townhouse design.

For instance, to reach their front doors, residents of this Capitol Hill townhouse development must go through the locked driveway gate…

Photo sent by Matthew Amster-Burton. (See Amster-Burton’s new book, Pretty Good Number One.)

…to this concrete garden awaiting them inside.

Photo sent by Matthew Amster-Burton.

Consider how those townhouse developments differ from recent cottage housing communities, which have historical roots in the early 1900s bungalow court cottages of Southern California and the garden city movement, which envisioned small towns surrounded by green belts. Cottage neighborhoods are designed around people rather than cars. They have smaller homes that are meant to appeal to one- or two-person households, and the parking area is shared among the residents, requiring people to park and then walk to their homes. Below is one such cottage community in White Salmon, Washington.

From Flickr user studio-d.

While townhouses are usually developed in multifamily zones, cottage communities are typically built in single-family zoning districts. Cottage developments usually require greater housing density to be successful. These projects also need less parking because the smaller units appeal to small households. Unfortunately, single-family zoning districts don’t always have the flexibility to allow this additional density or to reduce parking requirements. Where these cottage developments have been allowed, it has often been under a flexible zoning or incentive program.

Danielson Grove (below), a cottage housing development in Kirkland, Washington, was built under Kirkland’s Innovative Housing Demonstration Program, which encouraged creative solutions to meet housing demand. Planners in Kirkland ended up adopting many of the standards used in this community in a citywide ordinance.

From Flickr user studio-d.

Unfortunately, zoning incentives that allow increased density and reduced parking requirements to encourage such people-oriented neighborhoods aren’t found throughout Cascadia. Off-street parking requirements and car culture have too often resulted in communities dominated and designed around cars. Front porches, if they are built at all, have gotten smaller while garages have grown larger in many cities and towns.

Cities usually require off-street parking spaces for single-family homes, but they don’t specify whether they have to be enclosed. That’s not the case in the Seattle suburb of Beaux Arts Village, where new and renovated homes are required to provide parking for at least two cars in a carport or garage of at least 360 square feet. Reader Matt Leber sent in this photo of his garage, which dominates the single-family lot.

Photo sent by Matt Leber.

In Donald Shoup’s estimation, many neighborhoods “have become garagescapes—appearing to be a place not where people live, but where cars are parked—and the only obvious way to enter a building is with an electronic garage-door opener.”

The following “garagescapes” don’t exactly convey welcome. Garages at the front of these Tigard, OR, apartments serve as the primary entrance to the community.

Photo by Flickr user Brett VA.

Rather than front porches, garages dominate the streetscape in the Oregon neighborhood pictured below. The driveway curb cuts also create an undulating sidewalk.

Photo by Brett VA.

This apartment complex along a busy street in Tukwila, Washington, greets cars first.

Photo by Alyse Nelson.

As does this Portland garagescape.

From Getting to 2100 blog.

Garagescapes, dingbat buildings, automobile courtyard apartments, seas of parking—parking minimums have resulted in a variety of ugly architecture in Cascadia’s cities and towns. Zoning codes apply a general parking ratio across the landscape, with little regard for market conditions, transit opportunities, and the demographic makeup of neighborhoods.

As cities work to reduce automobile dependency, provide more affordable housing, and create more people-oriented places, it’s time to address parking regulations. The next time you see an unsightly apartment building or a sea of parking in front of a store, consider how parking rules have contributed to the ugliness. Off-street parking regulations are at the root of what makes Cascadian cities and towns less attractive and livable.

This article edited by Ina Chang.

Sightline Institute researches the best practices in public policy for a sustainable Pacific Northwest. Read more at daily.sightline.org.

But perhaps even more telling is the following chart, showing the same trends adjusted for population growth:

It’s sort of astonishing: measured per person, vehicle use on Oregon’s state-owned roads has fallen almost as fast over the last decade as it rose during the “driving boom.” Gasoline use per person is falling quickly too, due to a combination of reduced driving and improved efficiency.

To me, the implications are as profound as they are obvious: Oregon neither needs, nor can it afford, massive highway expansions. Oregonians are driving less, and any attempt to raise new transportation revenue from drivers—whether from tolls or from gas taxes—is likely to dampen demand even further. It would be nice if Oregon’s legislature agreed with me. But if Washington’s experience is any guide, convincing legislators that they don’t need a new, bigger highway can be an uphill battle.

Update:  By email, a thoughtful commenter wondered if my comments above suggest that I oppose using tolls to raise transportation revenue. The simple answer: NO!! I think that well-designed tolls are an essential tool, both for managing demand and for raising revenue. But transportation planners should recognize that tolls will reduce the demand for driving. Just so, a smart tolling regime can even boost the capacity of roads, by limiting peak-hour traffic congestion. Transportation planners should carefully consider the effect of tolls as they’re designing roads—so that they don’t overbuild the roads for no good reason!

Sightline Institute researches the best practices in public policy for a sustainable Pacific Northwest. Read more at daily.sightline.org.

Patrick Barber, flickr, used with permission.

Next week I’ll be driving my SUV pedaling to the Bicycle Urbanism Symposium at the University of Washington in Seattle. It promises to be a great event, jam-packed with some of the best thinkers on urban bicycling. And me.

My panel session is going to be lively, I think, given that the title is #winningthewaroncars. Erica Barnett of PubliCola is moderating and I’ll be joined by The Stranger’s Dominic Holden and Cascade Bicycle Club’s Evan Manvel. I’m on during Track 1 on June 20 from 11 to 12:30.

In the afternoon, Sightline board member and TransLink transportation planner Kamala Rao will take the stage from 1:30 to 3. Her panel session is on perspectives from Vancouver, British Columbia.

Sightline Institute researches the best practices in public policy for a sustainable Pacific Northwest. Read more at daily.sightline.org.

Photo by Alan Durning.

I have not owned a car in seven years, but I do own a garage. It’s pictured above. In fact, I am legally required to own an off-street parking space; that’s written in the land-use code for my city, Seattle, as for virtually every city. The driveway that leads to my garage, meanwhile, eliminates almost exactly one parking space from my street. Parking in front of a driveway is illegal, and a regular curb cut is almost exactly the size of a parking space, as illustrated below.

Photo by Alan Durning.

The net effect—one mandatory off-street parking space plus one car-less household—is a one-space reduction of parking supply on my block. Repeat: my obligatory driveway and garage deprive the universe of one on-street slot. This is ironic, but it’s only the tip of the irony iceberg where car-storage is concerned.

If I did own a car to keep in my garage, the net effect would no longer be a net reduction. It would be zero. My driveway subtracts one on-street space; my garage adds it back. Think about that for a while. The 4.6 million single-family houses in cities across the Northwest, and tens of millions more elsewhere, are each required to have at least one off-street parking space. Yet many of these city rules add no net parking spaces to their cities’ supplies. Worse, if you’ve ever narrowly escaped a car backing out of a garage, or almost backed into someone while you were driving, you can quickly grasp the fact that all these millions of mandated off-street parking spaces turn sidewalks into danger zones, especially for children and the disabled.

Clearly, parking rules can lead to absurd and unwelcome results. In fact, I will argue in this new series, they have surprisingly pernicious effects not just in single-family homes but across entire cities. Requirements that builders provide ample quotas of off-street parking spaces worsen traffic, multiply collisions, push up housing prices, dampen business profitability, amplify sprawl, and pollute both air and water. Parking rules are a surprisingly potent hidden force shaping—or misshaping—our communities. Fortunately, new approaches and new technologies allow better ways to manage parking, and these better ways turn out to be among the biggest opportunities open to cities for improving residents’ lives.

I’ll get to all of that soon. I promise. But let’s go back to my garage. Understanding how off-street parking rules for single-family houses pile up ironies, absurdities, and injuries is a case study of the larger dynamic of urban parking.

Consider this: You’re allowed to fill your garage with your stuff while you store your car in the city right of way. But you are not allowed to fill your garage with your car and store your stuff in the city right of way. Well, not for long. For a couple of days, you can probably get away with leaving a moving crate (like the ones pictured) at the curb. But if you tried to keep your stuff crated at the curb year-round, just as you can keep your car, you’d face stiff fines and citations.

Photo by Alan Durning.

On-street parking spaces are real estate that belongs to the public. They can be extremely valuable. The land under my house is worth more than $38 per square foot, according to the King County Assessor; Zillow implies a value above $45 per square foot. My lot, like many urban lots across Cascadia, is 50 feet wide. The curb parking area in front of it is therefore 50 feet long; it is about eight feet wide. Were it not for my driveway, three cars could park there. Because of my driveway, two can. It’s 400 square feet of land. If it’s as valuable as my land, at the Assessor’s valuation, it would be worth more than $15,000. Yet the city of Seattle gives away use of this public asset for free. And the city, like all cities, gives it away for only one purpose: storing private motor vehicles. I can keep cars, trucks, or motorcycles there. I cannot keep my bicycles there, though: it would be illegal for me to put a bike rack at my curb and lock my Trek and my Burley bike trailer to it. Walking stroller? No. Granny cart? No. Long board? Razor scooter? Shoe rack? Nope!

My garage is unusual in one way: I am the rare owner of a single-family house in the Northwest who has no private car. But the fact that my garage does not shelter an automobile is not at all unusual. Many garages never do. Garages store stuff, not motor vehicles, much of the time. One detailed, nine-year study of 32 middle-class families in southern California found they had so much stuff in their garages that only one fourth of them could fit their cars inside.

I asked around among my friends. One neighbor’s two-car garage (pictured below) is like something out of the Storables catalog, and thanks to its masterful engineering, it can still accommodate one small, electric car.

Photo by Ron W.

Other friends report that their garages are full of exercise equipment, bicycles, lawn mowers and other tools, camping gear, patio furniture, Costco loads, and the occasional ping pong table. Few keep cars in their garages. Here are excerpts from about 30 friends’ lists of what they keep in their garages:

• a set of half-refinished dining chairs
• one old kitchen sink
• a boat
• boxes and bubble wrap that I might need some day and chickens (until they are big enough to go outside)
• a playroom for my kids
• files that need to be culled through and probably thrown out
• storm windows
• band’s practice space
• old tax records
• books that don’t fit in the house
• toys that will never be used by my family
• a piece of a bowling alley and a wall-size bay window
• last summer’s jams and preserves, family memorabilia, my dad’s chaps from when he broke horses for room and board, his Arctic parka used to survey the North coast of Alaska, my old Royal typewriter and 100 other things
• an old rat cage, leftover wine from the wedding, dried leaves, dust, spider webs

One well-off friend who owns two two-car garages reported that her family still lacks room to keep more than one of its cars inside because the garages hold “boxes of papers, stuffed animals, etc., belonging to daughters, a saddle (it’s for sale!), an antique French food safe that I want to refinish for my grand-daughter’s bedroom, 30 years of crap from our previous house.”

Many garages hold everything but automobiles. Kathleen Ridihalgh of Seattle uses hers for kid stuff and a wood shop (below).

Photo by Kathleen Ridihalgh.

Paulo Nunes-Ueno, who runs employee transportation programs at Seattle Children’s Hospital, uses his as a bike corral and to store a spare mattress for guests.

Photo by Paulo Nunes-Ueno.

Seattle is not alone in requiring one off-street parking space per single-family house. Portland, Vancouver, BC, and some other large Cascadian cities have the same rule. In fact, virtually every city in greater Portland has this standard, because the regional governing body, Metro, has put a ceiling on parking requirements at one space per house. Most suburban Cascadian cities require two off-street parking spaces per house. Meridian, Idaho, a suburb of Boise, goes further. It requires two spaces for a one-bedroom house, four spaces for a two- to four-bedroom house, and six spaces for a house with five or more bedrooms. (I have listed many Cascadian cities’ parking standards below this post.)

A parking minimum of two (or more) is even worse public policy. Like a one-space minimum, a two-car minimum sometimes yields no net spaces: many builders planning two-car garages install double-wide driveways, which block two on-street spaces. Worse, as I’ll argue in subsequent articles, off-street mandates tend to glut the market for parking spaces and trigger a chain of cause and effect that ensures massive subsidies to driving. Whatever the number, furthermore, required off-street spaces dramatically push up the minimum cost of building a house. Curb cuts, driveways, and parking spaces cost thousands of dollars. The requirements also result in more pavement getting poured, armoring our watersheds and increasing the quantity of polluted runoff reaching our streams.

Although some cities, such as the Seattle suburb of Beaux Arts, require actual enclosed garages at each single-family house, most cities simply require parking spaces. So I am forbidden to remove the garage in my house unless I provide another off-street parking space on my property in its place. With certain exceptions, this space may not be in front of my house. I cannot just declare the driveway my new parking space. My off-street place must either be inside a garage or beside or behind my house. Many people do, in fact, park their cars in their driveways rather than in their garages. Seattle, at least, allows this manner of parking. But unless the driveways extend beside the house and the car can be positioned beside or behind the house, those parking spaces cannot satisfy land-use code requirements for off-street spaces in Seattle, or in most other cities.

Because my house was built in 1925, long before Seattle imposed a parking minimum, if my house had never included a parking space, I would be grandfathered out of the requirement entirely. But because my house does have a garage, I am not allowed to remove it. Converting my garage to some other purpose would require me to install a new curb cut beside my house, which would be surprisingly expensive, according to a contractor I consulted.

I have lived in my house for 13 years. During those years, my garage has never contained an automobile. In 2002, I installed insulated wall-thick doors on the garage, carpeted it, and began using it as an art room for my kids. Later, it served other purposes, such as an overflow guest room. It is now a computer room, laundry-drying center, and outdoor gear locker (pictured below).

Photo by Alan Durning.

I am still in compliance with the law. If a city inspector ever asked for evidence of my parking space, I could open the garage doors wide, move the furniture aside, and reveal a fully functional, if carpeted, off-street parking space. The law says I have to have one, not that I need to use it.

Some home owners take their chances with inspectors. Pictured below is a Seattle house where the garage could no longer hold a car. The owners converted car storage to a sun room, so the property no longer satisfies the parking regs.

Photo by Ashley S.

Eliminating one-space-per-dwelling parking requirements for single-family houses would free many other families to do the same, putting their garages and driveways to better uses, improving sidewalk safety, and lowering the construction cost of new houses. Striking out parking standards would let people like me use our property as we wish. My garage doors, thick as they are, still leak heat around the hinges in the winter: in a post-parking rules world, I could replace them with a real wall. I could jackhammer and re-contour the driveway to allow a rain garden. And I could relinquish my curb cut, giving my neighbors an extra place to park.

My garage is a case study in miniature. The fate of the world does not hinge on it. But the ironic, absurd, and pernicious effects of parking rules evident from examining my garage begin to reveal the larger implications of parking standards. I will turn to the larger economy and politics of parking rules next time.

Pam MacRae and Mieko Van Kirk assisted with research for this article. Thanks also to the photographers and friends who shared their garage stories.

Appendix: Selected Cascadian Cities’ Off-street Parking Mandates

Cascadian cities that require one off-street parking space per single-family house: Burnaby, New Westminster, North Vancouver, Vancouver, and Victoria, BC; Seattle, Spokane and Vancouver, Washington; Eugene and Pendleton, Oregon. Portland Metro, a regional government covering most of greater Portland, has established a “maximum minimum” of one off-street space per single-family house for all municipalities in its region: cities may set parking requirements lower but not higher than one space per house. Almost all of them have chosen to require one space per house.

Cascadian cities that require two off-street parking spaces per single-family house: Abbotsford, Coquitlam, Delta, Langley, Maple Ridge, Pitt Meadows, Port Coquitlam, Richmond, and Surrey, British Columbia; Boise, Idaho Falls, Meridian (two spaces for one-bedroom house; four spaces for two- to four-bedroom houses; six spaces for houses with five or more bedrooms), and Nampa, Idaho; Bend, Medford, and Salem, Oregon; and Bellevue, Everett, Kent, Moses Lake, Tacoma, and Yakima, Washington.

Sightline Institute researches the best practices in public policy for a sustainable Pacific Northwest. Read more at daily.sightline.org.

To get a sense of how America will pack more people into its cities, head north to an alley that runs behind Petersham Avenue here. That’s where Ajay Kumar built a $300,000, Moroccan-themed cottage that sits in his backyard and will soon be occupied by his parents.

Mr. Kumar’s “laneway house” is part of a broader plan that encourages Vancouver homeowners to add rental units in their basements, attics and backyards. The hope is to reduce sky-high housing costs and increase population density throughout the city—including the single-family-home neighborhoods like Mr. Kumar’s that surround the city’s towering downtown.

Cities across the U.S. and Canada are liberalizing their zoning codes to allow multiple dwellings on a single lot. Planners like these “accessory units” because they steer growth to developed land and infrastructure, reducing the cost of city services. Such housing can allow seniors to live near their children. And the dwellings are smaller and cheaper—helping cities create more affordable housing.

Few cities have gone as far as Vancouver, which has seen real-estate prices soar after an influx of domestic and foreign buyers. In many U.S. cities, citizens might not tolerate changing the rules to boost population density. But other places, including those with high real-estate prices and housing shortages, are encouraging accessory units despite resistance from some residents.

“These units are one front in a giant war for how our cities are going to grow,” says Alan Durning, executive director of the Sightline Institute, a Seattle think tank.

The article reviews trends that will be familiar to those who have read my three ADU pieces, but it fills in the landscape beyond Cascadia. It also highlights the business opportunities for builders and explains the key role of real-estate economics and shifting demographics in driving up numbers of accessory units.

The best line may be from Jake Fry, a Vancouver, BC, builder, who comments on what’s required to create small, functional living spaces, “You have to treat the house like a sailboat.”

Sightline Institute researches the best practices in public policy for a sustainable Pacific Northwest. Read more at daily.sightline.org.

Hop on in! Google’s self-driving car. cc stanfordcis

Cars that drive themselves seemed like science fiction just a few years ago, but recent demonstration projects have shown that the technology is already here. Self-driving car technology, pioneered by Google, has advanced so quickly that its ubiquitous presence on city streets is now simply a matter of time. Boosters say that mass-market autonomous cars are only 3 to 5 years away; others estimate at least 10 years. No one doubts they are coming.

But ideas about how these cars will affect cities and the environment seem to be stuck in the past. People think of self-driving, or driverless, technology as something added on to personal cars. Personal cars, however, spend 95 percent of their time parked, going nowhere, and waiting until they are needed. It’s more likely that city dwellers will view this technology as a service, like calling for a taxi. In principle, an on-demand car service could offer the door-to-door mobility of car travel without the fixed costs and hassles of owning a car.

Self-driving technology could cause a societal shift away from private car ownership and toward vehicle sharing. Widespread use of on-demand car services would result in fewer vehicles, which would then transform urban land use. Cities could reap significant benefits: fewer parking lots, more relatively dense, walkable neighborhoods, cleaner air, and reduced carbon emissions.

A local car2go. Credit car2go, used with permission.

Car-sharing programs like car2go offer spontaneous, one-way, pay-by-the-minute rentals within a prescribed service area. Members use a smartphone app to locate a nearby car, get to it, swipe a card to unlock, and drive to their destination. When they get there, users park the car at the curb and walk away, leaving it available for the next user.

Now imagine a mash-up of this popular model and Google’s self-driving car technology. The car-sharing fleet could be retrofitted with self-driving navigation systems. (Let’s call the hypothetical startup company “Car2Google.” Of course, other car-sharing services like Zipcar or even traditional rental car companies could jump into the game.) Layering self-driving technology onto this system would allow people to order a car from a fleet and have the car pick them up. It’s a taxi service without the drivers. Users would summon a car with their phone and wait comfortably indoors. The car would call or text them as it approaches. Users would then hop in, talk on the phone, or nap while the car drives to their destination. Once there, they can just walk away. The service charges their credit card an amount based on the time or length of the trip.

In addition to improving car sharing for the 1.7 million people who already use such a service, driverless technology would expand the appeal to a wide range of people, including those who:

• are too young to drive;
• are too old or infirm to drive;
• have had their license suspended;
• are too drunk or stoned to drive safely.

Parents could safely deliver their children to or from soccer practice or play dates simply by ordering a vehicle for them. Elderly people who should no longer be behind the wheel and disabled people who cannot drive would still have mobility, with the travel arrangements made independently or by caregivers. And everyone would benefit from impaired late-night revelers having a safe way to get home.

Does this sound like a fantasy? Rapid changes just in the last year bring this idea a lot closer to reality.

• Driverless technology is becoming more reliable, safer, and cheaper. Google’s six autonomous vehicles being tested in California have already logged more than 300,000 miles without incident. A Romanian teenager and an Israeli company have created low-cost versions of a self-driving car.
• Auto manufacturers are running to keep up. General Motors, Ford, Volkswagen/Audi, Nissan, Toyota, BMW, Volvo, Cadillac, and Mercedes-Benz (which, like car2go, is a subsidiary of Daimler) have all begun testing these systems.
• Legal barriers are falling away. Nevada, California, and Florida have enacted laws allowing the use of self-driving vehicles for testing purposes. A similar law was introduced in Oregon in early 2013, but it died in the legislature.
• Car sharing is an established program ready for technological breakthroughs. The popular car2go already serves 18 cities in North America and Europe. It is adding more cities all the time.

Self-driving vehicles would vastly increase the efficiency of car sharing. When not being used, cars would drive toward potential users instead of sitting idle and waiting for users to come to them. Instead of having workers going out into the field to service the fleet, cars could go to a central location when on-board sensors or user feedback recommend maintenance. A vehicle would take itself offline, drive itself to be washed or have its oil changed, and then put itself back online when ready to pick up another customer.

Driverless technology would also allow for a greener fleet. Urban trips are usually short hops ideally suited to electric vehicles. And when the battery level drops below a certain threshold, an autonomous vehicle could go offline and drive itself to the nearest available inductive charging pad to recharge.

Many households are already giving up their second vehicle—or sometimes even their only one–in favor of a mix of car sharing, bicycling, and using mass transit. A convenient, self-driving shared vehicle service could accelerate this trend. Traditional vehicles would likely still be needed for camping trips or to pick up a load of gravel, for instance, but these specialty vehicles could also be rented, perhaps from the same company.

This scenario of a city buzzing with fleets of self-driving vehicles may sound futuristic, but existing technology can already do everything described here. Automated car technology can also be applied gradually, one element at a time. Commercial airliners and many transit systems are already nearly fully automated.

The legal system and insurance interests are predictably wary of self-driving cars, and it will take time for individuals to grow comfortable with the idea of taking their hands off the wheel and their feet off the pedal. But legalization has already begun in several states, the Internet is rife with remarkable self-driving car videos, surveys show popular acceptance of the idea, and Google’s test models have a spotless safety record thus far.

A Google rendering of what a self-driving car “sees.”

Although the future is murky and the impacts of this system are unclear, if such a service took off, cities could enjoy a wide array of benefits.

Less traffic. Studies have shown that each car-sharing vehicle takes between 9 and 13 privately owned vehicles off the road. When people pay for driving by the trip, they see the real costs; therefore, car-sharing members drive 44 percent less than personal vehicle owners do. Cruising to find parking spots would no longer be an issue, thereby eliminating a third of traffic in some urban areas.

Fewer parking spaces. More than a third of land area in some US cities is dedicated to car storage. If people shift away from personal cars and toward shared vehicles, most of those parking spaces would become unnecessary. Acres of empty parking lots and driveways in desirable locations would open up for more productive uses like housing, playgrounds, or parks. If the change happens quickly, urban land prices could tumble.

Safer streets. People are terrible drivers. Human error causes or contributes to more than 90 percent of car crashes. Getting behind the wheel is the riskiest thing most people do in a day. Self-driving cars would be programmed to never speed, make sudden lane changes, or let drunk or distracted drivers make life-or-death decisions. The lead engineer on Google’s project expects driverless cars to sharply reduce crashes of all kinds.

Cost savings. Personal car ownership costs about $9,000 per year. Among young people especially, rates of driving and car ownership are already falling. A convenient car-sharing service that saves money could convince people to sell their cars while allowing them to maintain their same level of mobility.

Environmental benefits. More efficient travel patterns, fewer vehicles, cleaner cars, and less driving overall would lead to better urban air quality and lower carbon emissions. Less land would be paved over for parking, reducing stormwater runoff and heat island effects. These sustainability benefits would be market-driven and would not require government subsidy.

As with any potentially disruptive technology, the benefits might not materialize in the way we predict, and the future might not be as rosy as it seems. Consider the techno-pessimistic future:

More traffic. Economists are quick to point out that people usually consume more of something when it becomes cheaper. If people can sleep or work on their laptops while in a car, perhaps they will drive more and commute even longer distances. We simply don’t know how much unmet, latent demand there is for vehicle travel. In addition, trips that previously did not exist would result from new users (children, blind people), people who shift from mass transit, and the self-redistribution of empty vehicles driving to the next user.

Sprawl. Currently, only a small number of workers are super commuters who live an hour or more by car from their jobs. But if technology can eliminate the fatigue and aggravation of driving, more people may choose this lifestyle. The boom of streetcar suburbs in the 1890s and, later, auto-oriented suburbs in the 1940s showed that new modes of transportation have big effects on where people choose to live.

Less safe streets. If fewer cars sit parked and more of them are constantly circulating, streets could become busier. Early testing has been very promising, but self-driving cars have not been set loose on the full range of chaotic real-world conditions such as erratic drivers, snow-covered streets, and software or mechanical glitches.

Job losses. Certain workers lose out in this imagined future. Cab drivers, parking lot attendants, transit workers (who will likely be displaced not only by driverless cars but also driverless buses and trains), car dealers, and repair shops will become less necessary. Other jobs might pop up to replace them, but it is uncertain what they would be.

Widespread adoption of self-driving cars might just be another techno fantasy that won’t ever come into being. After all, vehicles powered by fuel cells (or hydrogen) or jet packs never came to pass. But autonomous cars are different because they can arrive incrementally. Cars already have cruise control, anti-lock brakes, lane sensors, and parallel parking assist. Soon private cars will be able to operate autonomously but only on highways and only when you choose to turn it on, then on city streets, and then eventually as Car2Google. Early adopters could be freight companies, then city buses, and then courier services. Unlike other technologies, it can function without everyone using it or a massive new fueling infrastructure in place. Self-driving technology can be layered onto existing cars using existing streets.

The public policy response to self-driving cars depends on how likely they will come into widespread use and how soon. Taking the pessimistic view, if this will never be more than a niche phenomenon, we should let the geeks play with their toys and ignore them. Driverless technology might find use in long-haul trucks or trains, but it won’t change cities in any significant way.

But what if we are only a decade away from being able to cheaply add self-driving navigation to any vehicle and on-demand automated car services suddenly take off? If that happens, today’s cars-first development policies will have been catastrophically wasteful. For example, if fleets of self-driving vehicles take hold, ubiquitous local laws that require each building to have its own oversupply of free parking will have wasted billions of dollars and vast acreages of urban land. Just so, in a future with fewer vehicles traveling through the system more efficiently, committing ourselves to multi-billion dollar roadway expansions is an enormous mistake. Buildings, parking garages, and highways are 100-year decisions. There is a built-in inefficiency with mass motoring, where every adult owns an expensive, space-consuming piece of capital equipment that sits idle 95 percent of the time. Our grandchildren may look back on this era as a short-term aberration, solved by technology.

The timing of self-driving cars and their possible impacts are uncertain. Nevertheless, the future leans toward transportation as a shared service. For decades we didn’t have the technology to allow one car to quickly and easily serve the needs of many people. Despite the inefficiencies of everyone owning his or her own vehicle, rules and cultural biases made the idea of car sharing seem not only impractical but even contrary to human nature. But we now have the technology; Zipcar and car2go have proven the market; investors see opportunity; and change is coming very quickly.

Naysayers have questioned the viability of car sharing since 1998, when there were only four car-sharing vehicles in our hometown of Portland. Today there are more than 1,100 here, with a few more added every week. Car sharing hasn’t stalled or died; in fact, it has exploded in popularity. Adding self-driving technology into the mix could make the next phase of car sharing truly transformative for both users and cities.

Ben Schonberger is a land use planner at Winterbrook Planning. Steve Gutmann is a consultant with a keen interest in car sharing, bike sharing and other forms of networked transportation. Both live and work in Portland, Oregon. Jade Chan edited this article.

Sightline Institute researches the best practices in public policy for a sustainable Pacific Northwest. Read more at daily.sightline.org.

Vehicle travel on Washington’s state roads fell again last year. It was a modest decline—just 0.8 percent—but as the chart to the right shows, it was a continuation of a full decade of essentially flat traffic. In fact, WSDOT estimates that total traffic on state roads was slightly lower in 2012 than it was in 2002.

There’s really not much to say about the trends that I haven’t said before. The flat-lining of traffic is due not to one single factor, but to many. Higher fuel prices are discouraging driving. Baby boomers have aged past their peak driving years. The “millennial” generation is driving less. Mobile and internet technologies make transit more convenient and rewarding. And the popularity of compact neighborhoods lets more people live in places where they don’t need to drive much.

And of course, I should mention a key fact that is getting overlooked in today’s transportation debates: the flat-lining of vehicle travel has occurred during a period when the state has done little to expand the urban highway network. And as a growing body of research suggests, driving in major metropolitan areas grows roughly in lock step with road space. Which makes me despair about the latest proposals for highway megaprojects in Washington’s major cities.

Sightline Institute researches the best practices in public policy for a sustainable Pacific Northwest. Read more at daily.sightline.org.

Rain garden, Lisa Stiffler.

In the stormwater world, if a rain garden is releasing more pollution into the environment than it’s capturing, word gets around.

So when the city of Redmond crunched its first flush of data from a new roadside rain garden and discovered the water coming out of it was tainted with alarming levels of phosphorus, nitrates, and copper, the stormwater community took notice. Washington State regulators went on the record to say that they would be studying the data and possibly revising their rain garden recommendations. Proponents of the technology fear that the results will be overblown and exploited by skeptics of so-called low-impact development solutions.

But even city officials in Redmond caution that they’re far from giving up on rain gardens.

“It definitely has not lost its merit in my mind,” said Andy Rheaume, Redmond’s senior watershed planner.

Indeed, there’s a decade worth of data showing that rain gardens and related “natural” technologies are effective at treating polluted stormwater runoff. They can do a terrific job soaking up the renegade rain water, diverting it from house basements and preventing it from scouring streams or causing overflows of sewage. And numerous studies demonstrate that rain gardens will filter out and capture a toxic mix of heavy metals, petroleum pollutants, particles and nutrients. In fact, the Redmond rain garden did treat some of the pollution gushing into it.

But rain gardens aren’t fool proof. Depending on the design of the system and the soil mix that’s used, a rain garden’s ability to remove pollutants can vary—and vary dramatically.

So what is a city or county stormwater engineer to do? Don’t panic.

“We’ve been promoting the message ‘Don’t throw away the baby with the bathwater,’ ” Rheaume said. “We’re pretty sure that (low-impact development) is here to stay.”

New Street, New Rain Gardens

In fall 2011, Redmond took advantage of a road-building project to construct some green stormwater infrastructure at the same time. The city installed pervious concrete sidewalks and three rain gardens that stretched a combined 410 feet along 185^th Avenue NE. The rain gardens, or “bioretention systems,” collect and absorb water from about one-quarter of an acre, including arterial roads that are surrounded by industrial use.

Cross section of Redmond rain garden.

Because the rain gardens were situated above an aquifer that provides the city’s drinking water, engineers lined the cells of the gardens with an impervious geomembrane to stop the runoff from seeping into the groundwater.

The bioretention systems were built according to Washington standards with 18 to 36 inches of “bioretention soil mix” that was 40 percent compost and 60 percent sand. The soil was planted with grasses and small shrubs. Beneath the soil layer was 6 to 8 inches of sand, 3 inches of pea gravel, and 11 inches of gravel backfill in the lowest layer (see diagram in Figure 4).

In the gravel layer, the engineers installed 8-inch underdrains that were designed to carry overflow stormwater out of the rain gardens and into nearby Bear Creek.

Given that the city depends on groundwater for drinking, officials wanted to know if the stormwater carried contaminants that could pose any risk to residents should it percolate into the aquifer. Stormwater regulations advise that engineers not concentrate stormwater runoff near stores of drinking water. But in truth there’s not a lot of data in the Northwest on what’s seeping out of rain gardens. To help answer this question, Redmond officials received a grant from the Ecology Department for $500,000, which covered 75 percent of the monitoring project; Redmond paid the remaining $165,000.

So three months after construction wrapped up, from February to July 2012, researchers monitored one of the cells. They grabbed stormwater samples where it entered the rain garden and as the “effluent” flowed out of it.

By taking the samples so soon after construction, researchers knew they were collecting some of the first flushes of water that would likely have unusually high levels of nutrients from the soil’s compost. But even with these expectations, the results –– at least for some of the chemicals –– were worrisome.

Rain garden, Lisa Stiffler.

The Trouble with Compost

Scientists have known for years that rain gardens can be finicky.

In Michael Dietz’s 2007 review of low-impact development strategies, he reported widely varied performances from rain gardens tested in Maryland, New Hampshire, Connecticut, and North Carolina. All removed metals including copper, lead, and zinc. But while most rain gardens effectively captured phosphorus and nitrogen-containing pollutants, in a couple of cases they released more of these pollutants in the effluent than they trapped.

Then in 2012, the East Coast’s rain garden rock stars William Hunt, Allen Davis, and Robert Traver teamed up to deconstruct bioretention systems. Their publication gave point-by-point advice on how to tweak rain gardens depending on which pollutants you’re most concerned about removing.

Want to clean petroleum pollutants out of your water? Don’t forget to spread a couple of inches of mulch on your garden, the scientists advised. If nutrients such as phosphorus, nitrogen, and nitrates are your targets, dial back the amount of organic material, including compost.

The soil used in a rain garden has a big effect on what seeps out of it, experts say.

“We and others have known this for years and continue to work on media,” wrote Davis, a professor in the University of Maryland’s Department of Civil and Environmental Engineering, in an email exchange.

“Compost will leach (phosphorus) and some composts will leach a lot of (phosphorus),” he wrote. “This has been known for many years.”

So here’s the challenge: How do you build a rain garden that contains enough organic material to support plant life, hold enough water through the summer, and create a habitat where pollutant-gobbling microbes will hang out, but not add so much compost that the garden disgorges too many nutrients, potentially fouling waterbodies downstream?

Washington State’s Stormwater Management Manual for Western Washington calls for 35 to 40 percent compost in the soil mix for rain garden systems. Scientists at Washington State University are investigating whether lower amounts of compost can keep plants happy while releasing lower levels of nutrients. They’re also looking at whether compost that’s sat around and aged for a while will shed less phosphorus and nitrogen.

Redmond’s Numbers

Roadside rain garden, Lisa Stiffler

In Redmond, automated devices collected runoff during storm events, resulting in eight separate samples for nitrogen, phosphorus, copper, and other pollutants.

Nitrogen in the form of nitrate and nitrite is particularly worrisome because high levels of these chemicals in drinking water can cause “blue baby syndrome” in which the nitrate binds to hemoglobin in the blood, robbing oxygen from the baby’s cells. Phosphorus is a problem primarily when dumped in rivers, lakes, and enclosed sea water where it can trigger harmful blooms of algae. And copper is known to cause problems for salmon and other aquatic organisms.

The results from Redmond showed dramatic increases in the amount of pollution leaving the garden, at least for certain chemicals:

Average Amount of Pollutants Entering and Leaving Redmond Rain Garden* (mg/L)

By contrast, the garden did a good job of filtering pollutants including fecal coliform, motor oil, and zinc. In those cases, the levels in the effluent leaving the rain garden were lower than in the stormwater that entered it.

Curtis Hinman, who leads the green stormwater research at WSU’s stormwater center in Puyallup, said the data were high by comparison to other studies and research that he’s done.

“We haven’t seen any numbers like that ever, even remotely close,” said Hinman, whose rain garden pollution results have not yet been published.

Stormwater testing facility at Washington State University’s Puyallup campus; Lisa Stiffler.

In the Northwest, the cities of Seattle, Portland, and Tacoma have sampled pollutants flowing out of some of their rain gardens.

In Seattle, scientists tested runoff as it flowed into and exited a rain garden on NW 110^th Street in a residential neighborhood in the northwest area of the city (Table 2). The rain garden is composed of 12 individual bioretention cells that allow the water to pour from one to the next, and the water was collected from the first and eleventh cells.

Researchers in Portland sampled stormwater runoff that flowed out of two rain gardens at the Oregon Zoo parking lot. They compared those values, which were collected about six months apart, to untreated runoff sampled at the same parking lot (Table OZ-3).

Officials in Tacoma have started monitoring the water going into and out of bioretention systems at R Street and 44^th Street in the Salishan residential development (see “Context” slide in this presentation).

It isn’t fair to do a rigorous apples-to-apples comparison of these rain gardens to the Redmond system, as the size, designs, compost mix, and age of the facilities are different. But even with these limitations, they can still provide some useful trend information.

If you compare the runoff entering and leaving each garden (or in Portland compare the rain garden runoff to the untreated stormwater), you see that the nitrogen and phosphorus values are frequently higher in the water exiting compost-containing rain gardens.

Comparison of Pollution in Runoff Entering and Exiting Northwest Bioretention Facilities**

And again, given caveats big as a stormwater settling pond, you can also compare the concentration of pollutants leaving the green stormwater facilities.

Amount of Pollutants Leaving Northwest Bioretention Facilities (mg/L)

Despite the risks of making such a comparison between very different systems, again it is clear that the Redmond numbers are often orders of magnitude higher than pollution levels taken from other Northwest rain gardens.

Potential Pollution Culprits

So what’s going on in Redmond to create such a spike in the pollution measurements? Could this problem be more widespread, or is this an isolated case?

The first thing to consider is the design of the Redmond bioretention system. The rain gardens on 185^th Avenue NE were built with an impervious lining to protect drinking water supplies and an underdrain, so in heavier rainstorms some of the stormwater filters through a few feet of soil and then drains quickly out of the garden.

In rain gardens without this design –– which includes most of the bioretention systems in the Northwest –– the water can soak as deeply as the soil allows and it might travel a long, long way before reaching groundwater or surface water such as a stream or lake.

Researchers have shown the more time the water spends infiltrating, the greater the opportunity for pollutants to filter out and stick to the soil, or get broken down by natural processes. Short cutting that pathway with an underdrain reduces that opportunity.

Gardening with compost, camknows, Flickr.

The second feature to address is the soil mix. To build a rain garden, you need organic material and sand, and that organic matter needs to be readily available, affordable, and –– particularly for public projects –– a source that is not proprietary. Enter the compost.

Washington State has a relatively extensive program of collecting yard and food waste and turning it into compost for public use. There are state standards that compost producers must meet for the concentrations of various pollutants including metals as well as nutrient levels. The regulations were crafted to make sure the soil was safe for gardens and yards –– not so that it would be optimal for rain gardens.

When the material used for the Redmond project was tested, it had 660 mg/kg of total phosphorus; the state rain garden guidelines recommend compost with less than 100 mg/kg of available phosphorus, which is not directly comparable to total phosphorus. The copper concentrations were 61 mg/kg (the state limit is less than 750 mg/kg), and nitrogen information was not available.

Compost producers weren’t “thinking about using this stuff as a stormwater filter. They were thinking about using this for someone’s garden,” Hinman said.

He and some others in the field suspect there was something unusual with the compost used in Redmond, that perhaps the manufacturer added manure or another nutrient-rich additive that wasn’t disclosed.

There “has to be a higher quality, more controlled material for this kind of application,” Hinman said. “The Redmond monitoring project brings up the question of consistency and reliability and our confidence in getting good (soil) media in the ground for bioretention systems.”

Pursuing a Solution

Redmond officials are planning to build another rain garden this summer, and they’re seeking funding to expand their monitoring program to include six installations.

Rain garden, Lisa Stiffler.

Their engineers will try different soil mixes in some of the rain gardens, including so-called “amendments” to the soil such as biochar and shredded cedar bark to better capture pollutants.

They will also try a design that incorporates a “saturation zone,” or an area of the rain garden where water will pool underground and create an oxygen-free environment favorable to chemical reactions that remove nitrates from the water.

Rheaume is eager to see what the monitoring will show at the new sites, as well as at the original rain garden.

“We want to see if this thing gets better,” he said.

The preliminary results from Redmond prompted the state Department of Ecology to remind stormwater folks in Washington not to use bioretention within 100 feet of a spring or a well used for drinking water, and not to install an underdrain if it leads to a phosphorus-sensitive body of water. In a move that surprised many, the state went a step further to say it’s considering whether to revise these guidelines to recommend against installing underdrains that ultimately empty into any surface water.

Planting a rain garden, robinsan, Flickr.

Ecology recently issued new regulations intended to increase the use of low-impact development stormwater treatments, including bioretention. Some cities and counties have challenged the rules, and all sides are waiting for the state’s Pollution Control Hearing Board to take up the issue later this year. Some stormwater experts worry that the Redmond data will be ammunition against Ecology’s regulations.

For now, Rheaume and Hinman will keep testing new soil mixes and designs to optimize what they both see as technology that can ultimately help the environment.

“We don’t have the silver bullet to say what the change is” that will yield better results, Rheaume said, “but we’re in pursuit of it.”

Editor’s note: On May 29, 2013, I added a reference to who paid for the monitoring research done in Redmond.

Sightline Institute researches the best practices in public policy for a sustainable Pacific Northwest. Read more at daily.sightline.org.

And there’s also been quite a lot of attention to ethanol—particularly the fact that US ethanol consumption has grown so quickly that refiners are starting to bump against the so-called “blend wall,” the point at which no more ethanol can be added to highway fuel without running into legal and/or technical troubles. (For more on the blend wall, see this Congressional Research Service report.)

But the two issues—declining gas consumption, increasing ethanol consumption—actually interact in interesting ways. Ethanol has about one-third less energy per gallon than gasoline does. Combining the slight declines in the volume of gasoline sold with steady increases in the amount of ethanol in the nation’s gas supply, the energy content of gasoline used on the nation’s roads has shrunk at a surprising clip. Take a look:

As the chart shows, US gasoline consumption peaked in 2004. Measured by volume, gas consumption has fallen modestly since then. But as ethanol in the gasoline supply grew, the energy in the average gallon declined—leading to a steep, 6 and 7 percent decline in the annual energy content of fuels consumed. All told, the energy consumed by cars and trucks has declined almost as steeply as it rose during the latter stages of the driving boom.

The upshot: we’re driving less; we’re driving more efficient vehicles; and we’re using less energy-rich fuels. It’s quite a change! And yet it’s been slow enough that it’s gone virtually unnoticed; and it’s certainly a change that hasn’t yet filtered into how we make decisions about our transportation future.

Sightline Institute researches the best practices in public policy for a sustainable Pacific Northwest. Read more at daily.sightline.org.

Besides keeping carpools and transit moving, the SR-167 HOT lanes have an additional value: they give researchers more nuanced understanding of how much people are willing to pay for a quick trip. And when we took a look at the SR-167 HOT lane data last year, the numbers surprised us: apparently, drivers really aren’t willing to pay much for a faster commute. Few drivers on SR-167 opted to the free-flowing HOT lanes, so HOT lane traffic volumes typically stayed low.

University of Washington PhD students Austin Gross and Danny Brent have taken our initial research several steps further. I’ll probably mention more about their work in a subsequent post. But in the short term, I was struck by their data showing how badly WSDOT transportation planners misjudged demand for the HOT lanes:

That’s right: actual HOT lane revenue in 2012 was about one-third of the “low case” projection that WSDOT made before the lanes were opened. That was likely due to two separate effects: fewer cars than anticipated using the HOT lanes; and lower toll rates needed to keep HOT lanes from clogging up. Both effects flow from flawed early assumptions and beliefs about how much demand there would be for driving in general, and for the HOT lanes in particular.

These findings don’t prove that HOT lanes are a bad idea! But they clearly have a bearing on today’s transportation debates. For well over a decade, the Washington and Oregon departments of transportation been planning massive highway megaprojects—wider urban highways, higher-capacity bridges, expensive tunnels, and more. And they’ve pursued these plans in the belief that bigger highways will ease congestion—and that drivers put a high value on congestion-free trips.

But the SR-167 HOT lane experiment shows that most drivers on that stretch of road simply aren’t willing to pay much for a fast commute. Which raises a question: given that drivers may not be all that willing to pay for a quicker trip, does it really make sense for taxpayers to invest so much in trying to give them what they won’t pay for themselves?

Note: just to be clear, the interpretations of Gross’s and Brent’s numbers are my own, not theirs. And their research goes much, much deeper into the specifics of pricing and driver willingness to pay; the chart above is just the tip of the iceberg. I’m very much looking forward to diving into their findings! And hat tip to GoodMeasures.Biz for the graphic!

Sightline Institute researches the best practices in public policy for a sustainable Pacific Northwest. Read more at daily.sightline.org.