Metrics have been used for years by NIMBYs, YIMBYs, municipalities, and numerous other housing-focused groups to fight for their desired outcomes. But most metrics that are employed are seriously flawed, because they tell us little about either the quality of existing places or the quality of developments proposed to replace them. A classic example is dwelling units per acre. 

The two places in the image above, Pienza, Italy, and Pruitt-Igoe, a housing project in St. Louis, had roughly the same number of units per acre. Pienza is such a great place that it has been designated a UNESCO World Heritage Site. Pruitt-Igoe was so notoriously violent and inhumane that on the day of its demolition, former residents accompanied the countdown with chants of “Blow it up! Blow it up! Blow it up!” Units per acre is such an unintelligent metric that it can’t tell the difference between utopia and dystopia. As the Eagles sang in “Hotel California,” This could be heaven or this could be hell …

Quality-blind metrics that can’t tell the difference between the best and the worst of places have long prompted me to oppose all architecture and urbanism metrics, but I’ve come to realize recently that some metrics actually can tell us quite a lot about the quality of the place they are measuring. I presented more than 40 such metrics at the International Making Cities Livable symposium in Cortona, Italy, last fall. What follows is a dozen of those metrics, one for each foundation of the Original Green. 

At this point, the proposed metrics include only what to measure but draw no conclusions about normative ranges, calibration to places, or other characteristics. The intent is to post the 40-plus metrics on a wiki and invite urbanists to comment and also to propose their own quality-based metrics. The ultimate goal is a tool able to measure both existing conditions and whatever project is proposed to replace them, and draw a meaningful conclusion as to whether the proposed project is an upward or downward trade.

Nourishable Places: Neighborhood Markets/720 Acres 

Before getting into the particulars of this metric, it’s important to understand the basis of the acreage denominator in this and several other metrics. The diagram in the upper right of the image above highlights problems associated with two common calculations of “walking radius,” or “walk shed.” The Perry Diagram developed in the early 20th century proposed a five-minute stroll as the maximum distance U.S. residents would walk instead of driving, and it came to be widely known as the “quarter-mile radius” because most people can walk a quarter-mile in about five minutes. Unfortunately, the radius is a mirage because humans don’t fly—our walks are traversed along streets, sidewalks, and alleys. The upper right diagram shows that in a regular grid, a quarter-mile walk (or any walking distance, for that matter) gains access to a diamond-shaped land area substantially less than that which a quarter-mile radius includes. And for some who use the square area with height and width being a half-mile (quarter-mile from center to edge), the diamond of actual walking distance along streets is exactly half the land area of the half-mile square. 

The acreage used throughout this post is based on the diamond diagram of actual distance walked along streets in a regular grid. A five-minute walk from the center to points of the diamond includes 80 acres (0.5 miles square = 160 acres / 2 = 80 acres). A 15-minute walk from the center to points of the diamond is 720 acres (1.5 miles square = 1,440 acres / 2 = 720 acres). So the 15-Minute City includes 720 acres. Using these calculations, a two-minute walk on the diamond includes a bit over 12 acres. The acreage denominator was used many times in the metrics of my IMCL presentation, but most of those have been edited here in order to demonstrate other means of measurement. 

The term Neighborhood Market, as used here, represents a robust neighborhood-scale establishment which stocks mostly food and drink items but also a number of other household goods as well, as was once found in the classic American corner store. A second type not pictured here is the Food Market, a smaller-scale establishment with only food and drink items. Its metric is markets per 80 acres. 

It’s important to note that there is no judgment made as to whether one Neighborhood Market in 720 acres (15 minutes) is ample or not; it’s just the yardstick used to measure the frequency of Neighborhood Markets. Where I live, we have both a robust Neighborhood Market and a pharmacy that’s a 20-minute walk away, and I’ve made that walk countless times because the walk is so interesting due to its high Walk Appeal. And a 20 minute walk = a 1,280 acre diamond. 

Accessible Places: Thoroughfare Length/View Change 

The more quickly your view of adjacent buildings changes, the more interesting it is to walk by them. A building that requires 30 seconds to walk past is positively boring compared with a building that can be traversed in 8 seconds, for example, all other things being equal. Storefront displays can help, but they rarely change more than once or twice a season, whereas building widths are, obviously, much more “permanent.” 

Serviceable Places: Properties/Acre 

Jane Jacobs noticed decades ago that the more properties there are per acre, the more diverse the businesses and their offerings are likely to be in that district, a metric that has come to be known as the Jacobs Diversity Standard. It’s noteworthy that diversity need not be scripted; with more properties in a given area, there is greater likelihood for businesspeople to produce a naturally occurring richness of product and service offerings.

Securable Places: % of Daylight Hours Free-Range Children are in Civic Spaces 

This is a strong test, because few parents will let their children run free in public if there is much of a chance that ill-intentioned people might lurk nearby. The highest standard of activity is hide-and-seek, because who would let their children hide in the presence of possible danger? 

Lovable Buildings: Average Age of 12 Oldest Buildings/City Age 

The closer a city’s oldest buildings are to the age of the city, the more likely they have proved to be so deeply lovable that the buildings’ owners and the city will keep them well-maintained. A better but far more difficult metric would be the median age of all buildings divided by city age, but the data collection required for this would be immense for even a medium-sized city. This highlights an underlying principle of all of my metrics: look for simple indicators of complex conditions. Put another way: How few measurements are needed to get a reliably accurate metric? A system requiring days or even just hours to produce a trustworthy measure of a place is clearly more powerful than a system requiring months or years to reach a similar conclusion. 

Durable Buildings: Life Expectancy of Prevailing Shell Assemblies 

This metric sounds difficult to produce because the most thorough means of achieving it would be through a census of all buildings in a place, which would be an immense undertaking. A much leaner approach would be that which political pollsters use: a scientifically based sample that is a tiny fraction of the overall building count. Only the top three to five shell assemblies should be included, because deep outliers can skew the overall metric. 

Adaptable Buildings: Average Number of Building Corners 

This metric is a classic example of a simple indicator of complex conditions. Architects have been taught “form ever follows function” ever since Louis Sullivan first wrote those words and Frank Lloyd Wright later merged them into “form and function are one.” Unfortunately, a building designed like a glove around the hand of function is highly unsustainable because once the function disappears or its physical implications change in major ways, the building becomes obsolete. The most adaptable buildings are simple in form and able to be used for many things over time. The best test for simple massing is a count of the exterior building corners in plan. A corner test is also a good test for economy, because buildings that break and wiggle all over are likely to be a lot more expensive than those with calm compositions. 

Frugal Buildings: Linear Feet of Thoroughfare/Street Tree 

At first glance, this metric seems completely disconnected from the frugality of buildings, but the most effective way of reducing building heating and cooling usage isn’t to spend a lot of money on marginally more efficient equipment. Instead, the best process is to condition ourselves to the local environment to achieve a state known as Living in Season. Doing so allows us to throw the windows open on all but the most extreme days of the year, at which point we discover that there is no equipment so efficient as that which is off.

We condition ourselves best to Living in Season by enticing ourselves outdoors into great private realms like courtyards and other outdoor rooms and great public realms like streets, plazas, squares, greens, parks, and playgrounds. Great public realms have the added benefit

of requiring walking, which better helps condition us. Street trees are the most significant elements in enticing us out into great public realms because there are so many virtuous cycles spawned by street trees. Hence, as disjointed as it seems, street trees are some of the most important elements in reducing energy use in buildings, not because they change the buildings, but because they change us. 

Learning Society: Elementary Schools/2 Square Miles 

When the weather was decent, I walked a bit over a mile to elementary school with a group of kids from my block, but that was beside a five-lane arterial whose only redeeming virtue was that the sidewalk was set back 15 feet from the travel lanes with an open drainage ditch in between, so an out-of-control car would by highly unlikely to ever reach the sidewalk. A 1-mile walk on the diamond introduced in Nourishable Places encompasses 2 square miles of catchment area. This doesn’t imply that it’s OK for a group of kids to walk a mile to school today just because I did so in the late ’60s and early ’70s, but it’s a metric I lived with for several years, so I know from experience that it can be done. And today, parents in many places accompany groups of kids to school in the morning and home in the evening in “walking school buses.” The school in the photo above, for example, has walking school buses on most days of the school year depending on weather conditions. 

Prospering Society: Neighborhood Range of Values (15:1 US, 40:1 Europe, Rent & Own) 

I know of no single metric that is a better predictor of grassroots economic development than the range of housing values within a neighborhood. Before the automobile, neighborhoods, hamlets, villages, and towns around the world had wide ranges of values because human transport and horse transport limited how large people’s Web of Daily Life could be. Many places had ranges of values significantly greater than 40:1 in the pre-internal-combustion-engine era; that metric comes from decades of research by famed Bahamian developer Orjan Lindroth, who observed that a 40:1 range of housing values (rent or own) is the threshold at which startup entrepreneurs had better-than-average chances of getting off the ground, and once they did, both the business owners and their employees could live there, reducing everyone’s transportation burden. 

I use the 15:1 metric for the U.S., even though it is 300 times better than typical development practice here because Orjan recommended backing off the globally-proven 40:1 range of values, which would be 4,000 times out of line with U.S. development practice, and because at 15:1, much grassroots economic development still works. We set out two decades ago to develop a neighborhood with a 15:1 range of values near Montgomery, Alabama, and we achieved it. The least expensive cottages sold for $165,000, just a few blocks from a $2.5 million mansion. Today, of course, they’re all more expensive, so you have to keep building the most affordable ones. The image above is Poundbury, England, King Charles’ development. It has a wide range of values, and it’s impossible to tell which units are social housing and which are market rate. If a wide range of values is good enough for the king’s town, why not your town? 

Entertaining Society: Third Places/720 Acres 

Most would know that a Third Place accompanies home (First Place) and work (Second Place) as the places we inhabit most, if you don’t count the car. It can be a cafe, a bar, a coffee shop, or other venues where “everybody knows your name,” and where you’re free to buy something and stay awhile. This and the Nourishable Places pattern near the beginning are the only two in this post that use the 720 acre metric of the 15-Minute City. As noted earlier, this is not to say that there should be only one Third Place in 720 acres. This image is from Paris, and in any given 720-acre quarter of Paris there are likely dozens of Third Places. The more, the better; 720 acres is simply the metric chosen with which to measure Third Places. 

Healing Society: Playgrounds/12 Acres 

Unlike previous acreage/square mile metrics, this one calibrates what is considered by many to be a healthy level: a two-minute walk to play. As noted earlier, a two-minute walk is a bit over 12 acres on the diamond. So a place with less than 1.0 dedicated play place per 12 acres is deficient, whereas a place with more than 1.0 play place per 12 acres is doing well. And play 

places can run the gamut, from parks to playgrounds with dedicated equipment to sport courts to inner-block rambles to splash fountains like the one pictured here. And because the measure is play places per 12 acres, most of them should be small; a basketball goal on an alley or rear lane counts as much as a splash fountain. At the end of the day, it’s simply a place to play.

All photos by the author.