Floor-area ratio, height limits, minimum parking: how density restrictions shape built areas

Urbanists often speak of density, I've written about why it is so important with regards to sustainable urban areas before. Density allows for services, businesses and jobs to be more in proximity to where people live, which makes motorized transport less of a requirement and more optional. But how to measure it? A traditional measure is the residential population by area, for example, people per square kilometer or square mile, or by hectare or acre. This measure has a big flaw: it counts only residential density, but what about jobs and commercial density? The downtown area in many cities all across the world is the most densely built area, yet by that measure, it would be of very low density because most buildings are not residential, and so few people actually inhabit the downtown area. One attempt to balance things out is to add jobs in an area to the residential population, thus you have a density of residents+jobs per area.

But the big problem with this measure is that it is quite hard to actually use that data in regulation and planning, because both people and businesses are free to move around, you can't compel X number of people or jobs to be in an area. You can only provide Y amount of buildings to allow them to be there, but people are ultimately free to settle there or not. And that is why we sometimes see alternative measures of density, especially in planning, like residential units per hectare or acre. So instead of counting people, you count dwelling units. However, this also has problems, because it's hard to include commercial areas in this measure. A single big box store can have millions of square feet of space, but it is just one commercial unit, so you obviously can't add this as one unit in that measure.

There is a measure of density which can be very helpful then, the Floor-Area ratio.

Floor-Area Ratio: agnostic measure of building density

The Floor-Area Ratio (FAR) is a ratio, so often a percentage, of the sum of the floorspace of buildings to the area of the lot. OK, let's do things with an example, let's take a 2-story house on a lot:

Suburban 2-story house

So, first, let's see what's the size of the lot on which it is built:

Size of the lot

 So the lot is 450 square meter (1 square meter is roughly 10,7 square feet).

Now, let's see how big the ground floor is:

The ground floor

Now, let's look at the second floor, which isn't as big.

The second floor

OK, so the first floor is 80 square meters, the second is 66 square meters, for a total of 146 square meters.

So the FAR in this case is (80 m2+ 66 m2) divided by 450 m2, or 32,4%. 

The attractiveness of the FAR is that it is use-agnostic and allows to compare residential, commercial and industrial buildings on an equal footing. It strictly calculates the density of the built area. It also doesn't care whether the developments are more "tower in the park" or "European traditional city block", it will tell you how much floor area people have to live or work in.

A modernist tower versus traditional European city buildings, which do you perceive as denser:

...the tightly-built 4-story buildings,...

...or the stand-alone 8-story buildings?

Thanks to FAR, we know both are equally densely built

Regulating FAR or not

So if FAR is use-agnostic and allows to compare the density of built areas, so it's a good measure of building density. However, should it bear the brunt of our planning regulations? Certain planning systems do already use it, France has used it for a long time, though it is phasing it out. Japanese zoning does use it even today. Many North American cities use it in their downtown areas.

But the important questions we should ask are: what do we really want to control? What are the impacts of decisions to regulate built areas in certain ways?

So is FAR really something we want to regulate directly? In general, I would say no, it isn't. There may be certain externalities to particularly dense developments like plunging areas into perpetual shadows or avoiding covering lots too much, causing major problems to sewers during rain, however, FAR is not the way to deal with those. For shadow-avoidance, height limits relative to the distance to the next lot are much more effective. For the reduction of surface runoff during rain, lot coverage limits are better. Of course, add these two limits together and you're essentially limiting FAR, but you're not limiting FAR directly, you're simply regulating certain forms to avoid problems, FAR just happens to be limited indirectly.

Oh, and if you want to limit traffic generated by developments... limit parking spots, not population. If you limit residential parking, then you limit how many cars there are to drive, if you limit commercial parking, then you limit how many people can go there in a car.

If there is one reason to regulate FAR, it is for economic reasons. The value of land being dependent on the density of revenue-producing building that can be built, restricting FAR can limit the value of land, which can be useful in certain cases. That is why I did refer to FAR limits in my post on incrementalism, as my focus was on the economics of urban developments. I focused on FAR to make sure that buildings that replace older ones are significantly denser to reduce the cost of replacing older buildings and allow newer, denser buildings to still be affordable. So in that case, my focus was the cost of construction of each square foot of living space. It is not an externality per se, just a way to control costs of land and housing within certain limits.

The impacts of certain building regulations

More importantly, I think we have to be cautious around building regulations, because these have important impacts that may not be apparently obvious.

For example, much has been written about Americans' ever-growing living quarters, bigger and bigger houses. Why is that? Well, this is a combination of minimum lot sizes, single-family only zoning and minimum off-street parking regulations, while at the same time Floor-Area Ratio is not directly limited in most suburban areas. 

All these regulations in effect limit how many units per hectare (or acre) can be built. The strongest limit is the combination of lot sizes and single-family zoning, which means that you mandate a large lot (say 6 000 to 10 000 square foot) and you say only one housing unit can be built on it. Well, in that case, why wouldn't you build bigger and bigger housing units then? Up to what people can afford? If you build a small house on that lot, that is a waste of a lot, building smaller houses won't increase density and will reduce the profit margin of the developer. If there's no regulation to impose a smaller house, why build one?

Minimum parking regulations have a similar impact, in that the number of units that can be built will be dependent on the number of parking spots that can be built economically on the lot. For example, in Japan, you can see small buildings full of studio apartments like these a bit everywhere:

Small studio apartments typical of Japan, rendered in Sweet Home 3D, 12 units on a 350-square meter lot (around 4 000 square feet), more than 300 units per hectare, FAR 70%

These are possible because the minimum parking regulation are very low, I've heard that one parking spot per two apartments isn't rare, and regulations don't control much the number of units that can be built on a lot, there is no single-family zoning. So you can have a lot of very small apartments on a small single lot, yielding high densities of 200 units per hectare or more (80 per acre). Of course, these are very small, so fit only for one occupant, but even with just one occupant, that yields a population density of 20 000 people per square kilometer or more, or more than 50 000 per square mile. It also makes small, very cheap apartments easy to build anywhere, providing a cheap housing option for singles.

Now, why don't we have something like that in most North American cities? Well, because most towns have strict minimum parking regulations, some of which don't even differentiate 2-BR apartments from small studios and mandate 1,5 parking spots per apartment, no matter how big or small. So if we take this previous building and build 18 places of parking, what do we get?

The previous studio apartment building but with typical North American off-street parking regulation, FAR 25%

In this case, density is actually cut to a third as the lot is three times as large to accommodate the parking. In that context, what is the point of building that type of building? The revenues from the lot would be very low. It is much better then to build much bigger housing units, say 2-bedroom apartments, so that you can waste less of the lot for parking and get better revenues from it. For example, they could build something like this:

Apartment building with 6 2-BR apartments, FAR 70%, 65 units per hectare

This type of building is much more likely to be built in the North American regulatory context because you can get higher FAR, and it also has higher population density than the studios with 18 parking spots, because each unit will have 2 or 3 people in it.

An interesting point to consider is what happens to the single individuals in North America that seek cheap housing options, since they are largely deprived of the small 1-Bedroom apartments due to regulations restricting the number of units that can be built per area? Well, they share apartments with roommates. Indeed,  becoming roommates is the way consumers have devised to go around the excessive parking and density limitations imposed by North American planners. It is not a desirable situation, but when in a pinch, people will do it.

So North American regulations that limit the density of units but are less restrictive on FAR will result in bigger housing units as developers will build big units to maximize profits.

Policies that do the opposite, meaning limit FAR but are favorable to subdividing buildings in many units thanks to a lack of minimum lot size and low or no minimum parking regulation will have the opposite effect: tend to increase housing density but reduce the size of units.

That is because, all else being equal, in general, the value of bigger housing units is greater than the value of smaller units, but the value PER SQUARE FOOT of smaller units tends to be higher than that of bigger units. So to maximize revenue, if the number of units is limited by regulation, then the bigger the units, the more revenue they will bring in. If on the other hand you limit the amount of square feet of floor developers can build but do not limit the number of units, then they will have a tendency to build more, smaller, units.

There are other impacts that follow other policies. For example, in certain cities, the height and/or number of stories of buildings will be limited, but basements do not count as a story, the result will be plenty of houses with basements and basement units (which I regard as an undesirable effect, especially in highly populated areas, no one wants to live in a basement and learn to tell people by their ankles).

If FAR is limited but balconies do not count, expect large balconies to happen.That is possibly what happened in Japan, as balconies in condos can be very large even when units are small. For example, here is a floorplan of a condo in Tokyo, found on Suumo.JP:

This 70-square meter apartment has a balcony of nearly 13 square meter, nearly 16% of the floor is a balcony, but it doesn't count towards the FAR limit

The United States represent an extreme of the dynamic of how limiting the density of housing units can yield bigger and bigger housing units. The opposite of that is India, where planners erroneously believe that limiting FAR will limit population density rather than simply reduce the size of living quarters, resulting in terrible overcrowding and living conditions for tens of millions of Indian citizens. Stephen Smith at Market Urbanism has even called the relaxation of this FAR limit the most needed urbanist reform in the world. And it is hard to disagree when one sees the results.

 Conclusion

So, the Floor-Area Ratio, it's a great way to measure building density, however, it isn't a very good vector for planning and regulations, unless one starts an approach like the one I described for incremental city building. It is important to understand that developers and consumers have a tendency to act in a way planners don't expect to maximize their own benefits regardless of the goals of regulations set in place. It is thus important to understand the possible effects that various ways of controlling the built area may have, and to do that, we have to understand what economic actors want and how they think, for they show great innovation in skirting around regulations.

Carpooling: does it make transit irrelevant?

And now, for the latest in our series of "things hardened motorists say make transit irrelevant so we shouldn't even bother investing in it": carpooling!

Carpooling is one of these ideas that, if you don't look at the details, sound positively magical in terms of efficiency. A private car has no deadheading and carpooling from a common origin to a common destination ensures a higher occupancy ratio than transit. Think about it, a bus can carry around 60 people, if it has on average 10 passengers, that is only on average 20% of capacity, the equivalent of a car with just the driver in. So with just one passenger, a car will have an higher average capacity utilization than a regular transit bus. Carpooling could also significantly increase throughput of existing roads. If every car carried 3 people instead of the 1,3 people they do at peak hour currently, then you could theoretically more than double the number of passengers per hour roads can carry.

On an economical level, some will point out that the cost per passenger-mile of cars driven alone is often equal or just slightly lower than transit (numbers that can be greatly debated). With just one passenger apart from the driver, the cost of car travel per passenger-mile becomes much less than transit's.

Furthermore, some point out that cities with low transit tend to have higher carpooling mode share for commutes:

Transit mode share vs carpooling mode share (source)

So, argument over? We should just cancel transit investments and focus on incentivizing carpooling instead?

Yeah, not really.

Why carpooling is not a replacement for transit

Don't get me wrong, carpooling is a great idea if you can manage it in your schedule. However, carpooling is a very inflexible mode of transport for the passenger. Essentially, carpooling is like a bus line that has only two stops and that runs once in the morning in one direction and once in the evening in the other direction.

Schedule of a bus line versus "schedule" of a carpool, which do you prefer? (Yes, I use 24-hour time)

So, in essence, all single occupancy car trips can be seen as potential carpooling lines, or even as some kind of express bus. In order for carpool to be a valid choice, you need:

A- To have the same origin and destination as another trip, or to be easily on the way

B- To need to leave in their morning at roughly the same time and to come back at roughly the same time too

Considering sprawl and the fact that arterials tend not to be residential (even worse for freeways), these two conditions are quite hard to fulfill. The time when they are most likely to be fulfilled is for the commute, as this is when the most trips are happening at the same time.

But wait, that's not all, with a bus line, if you miss one bus, you can take the next one, if you miss the carpool, you're screwed. If you want or have to stop somewhere while going to work or coming back home, it's hard to do it while carpooling, the passenger is captive of the schedule of the driver. Even worse for workers who have variable work schedules, which is more and more common. What if the driver has no overtime but the passenger has to stay at work 1 hour more to finish some task?

So it's no surprise that carpooling is largely fit only for a minority of people who happen to have very stable work schedules. Transit on the other hand has plenty of trips, allowing for much more freedom of movement.

So carpooling is not appropriate in most cases... at least it's still much more economical than transit, right?

Well... not exactly.

The big issue here is that, as I said, carpooling is not flexible at all, and commutes are just maybe 30% of people's trips. So if there is no transit in a car-dependent area, what does the passenger of a carpool do when he has to go somewhere else than at work? Well, in the end, he still has to own a car for when carpooling is unable to satisfy his mobility needs, which is most of the time. So carpooling doesn't eliminate the need for cars the vast majority of the time, and the basic fact about cars' costs is that fixed costs are very important, so not using your car doesn't cut down on costs all that much. Yeah, you save on gas and maintenance, and sometimes on parking and tolls, but the depreciation of the car is still there.

As I showed in a previous article, the cost per mile driven of a car varies greatly with the amount of miles driven, according to the AAA and CAA:

Cost in cents per mile per annual mileage, in blue the AAA, in red the CAA

So let's take one example of a 3-people carpool versus a case where everyone drives alone. If everyone drives alone, then each car is driven 10 000 miles a year, at a cost of 0,80$ per mile. But if they carpool, then one car still drives the same amount of miles and costs the same, but the two others are driven over 30% less miles, with costs per mile driven increasing to 0,95$ per mile.

So, what happens to costs?

Summary of miles driven and costs for the two scenarios

So overall, there is a cost reduction, but not as much as you'd think. Though miles driven are reduced by 20%, the total costs are reduced only by a little over 11% because of the fixed costs of ownership of the cars not used during the carpool.

Of course, you can make the argument that transit can also be the victim of this dynamic. However, as transit is a network with all-day service most of the time, the possibility of people to opt out of owning cars is much higher than with carpooling for the commute. And transit remains spatially more effective than cars even with carpooling. Even a bus with just 10 passengers occupy half as much road space as a car with 2 occupants. A bus that is full occupies nearly 6 times less road space than a car with 4 occupants.

So overall, transit can be a competitor to car ownership and travel the way carpooling can't really be.

Oh, and BTW, about carpooling declining with rising transit use, that is a mistake. Carpooling doesn't decline as a proportion of car trips as transit use increases, if carpooling has a lower mode share, it's just because CARS as a whole have a lower mode share.

Transit mode share versus the proportion of carpooling mode share over driving alone mode share

Another fact that pops up when looking at the data is that congested cities don't necessarily have higher carpooling mode share. Which underlines that private vehicle occupancy is not impacted much, if at all, by congestion. In other words, you can't trust increased carpooling to deal with congestion.

What about slugging?

There is a final argument for carpool: slugging. Slugging means having people drive to a park-and-ride parking lot somewhere, park their cars there then get picked up by other people to do the rest as a carpool. Theoretically, it can help ease the problem of coordinating trips by moving the origin of the commute to a common parking lot rather than people's homes.

Traditional carpool, Blue goes from his home (Blue dot) to Red's home (Red dot) then both continue to a common destination

Slugging: both Blue and Red head to a parking lot, where Red parks his car and continues with Blue to the destination

This can help indeed to make more carpooling possible. But it may cause capacity problems near the parking lot due to the high number of vehicles going there and picking up people. But the biggest flaw of this approach is that if you have a park-and-ride parking lot... why not simply serve it with shuttles instead of relying mainly on carpooling? Just run a bus from the parking lot to the destination, then both Blue and Red can leave their cars there and board a shuttle bus. This kind of express bus is very economical as they have few stops and tend to have higher occupancy, the AMT runs express buses for less than 0,30$ per passenger-mile in Montréal. This also reduces even more the need for parking and road capacity in areas with high job density.

Conclusion

So, what of carpooling? It certainly beats driving alone, so if you are one of the lucky ones that can use it, please do, and favoring people who carpool with HOV lanes is very defensible. However, carpooling alone doesn't solve the issue of carless mobility and its economic benefits are overestimated by neglecting the fact that carpool passengers still largely need to own cars on the side. If anything, transit may be complementary to good carpooling option as it gives a fallback to passengers if their ride doesn't show up.

The common origin of North American suburbs and Soviet towers in parks

So I read an article recently about the "Soviet City", (http://www.newgeography.com/content/004830-looking-back-the-ideal-communist-city) which made a link between the Soviet city planning and the urbanist movement. The author noted that, like urbanists, Soviet city planners were focused on walkability and transit, and sought density, building big concrete apartment blocs. She said that they were imposing their vision in an authoritarian manner, contrasting this with North American suburbs, that she describes as emerging organically from the desires of consumers. The whole piece is meant as a warning against urbanists not to impose their vision on an unwilling population.

You may consider this post as a rebuttal. I believe that despite the author's claim, both North American suburbia and Soviet suburbs (yes, they were suburbs, not cities) share many basic design points.

First similarity: both were planned from above and imposed on the population

The most glaring error of the text is that it supposes that North American suburbia is a spontaneous emergence from consumer preferences. The reality is very, very different. Though the United States as a whole likes to boast of capitalism and property rights, in terms of development policy, it is one of the most controlled countries in the world.

American elites in the middle of the 20th century were clear about their vision for the future of the country. The American Dream would be about owning a house on a plot of land, with cars to travel around, like a miniature version of the estates and villas of the rich. Renting was out. Mixed use was out. Multifamily housing was out... even outright "un-American" according to some of these elites.

As a result, American cities and governments adopted strict policies to make almost anything that wasn't suburbia was harder and more expensive to build... if not outright impossible.

Cities implemented Single-Family Detached (SFD) only zoning, forbidding anything else but detached housing in most of their area. Any attempt to convert houses to multifamily housing would face quick backlash from the defenders of this zoning. Regulations would mandate huge parking lots to make sure traveling by car was easy, even if they made walking, biking and transit very inconvenient.

The Federal Housing Administration offered mortgage insurance only to places that fit the standards of suburbia. Redlining, where whole areas were denied government-backed mortgage insurance, is often associated with race, but it was also singling out urban areas, based on ideas regarding urban planning that are opposed to best practices today (mixed use was wrong, street grids were wrong, cul-de-sacs were great, etc...).

Advantageous fiscal advantages were put in place for homeowners to make paying back a mortgage cheaper than renting.

Not only that, but State governments would destroy entire neighborhoods to run highways through cities to allow suburbans quick automobile access to entire cities, without which the suburbs would have been unable to sprawl farther as distances (in minutes) would be growing too great to support the sprawl. These highways would be free of charge to use, subsidizing suburbs that depend on them by using tax money from other areas. Transit would choke faced with this subsidized competition.

Canada has a bad tendency of doing whatever big brother America does, so much of these policies were imported North.

Of course, in a time of great population growth (the babyboom and mass immigration), when you destroy urban housing for "urban renewal", ban new urban housing from being built and subsidize sprawl, it is no surprise that sprawl is what gets built and where most people start living in. Whether or not there really was consumer preference for this type of housing, we will never know because of the imposition of that model and its subsidization. Price is part of consumer preference, an essential part of it, by subsidizing a certain lifestyle and increasing costs of other lifestyles, you change what consumers will opt for.

Second similarity: Soviet suburbs and North American sprawl are built based on the same anti-urban modernist ideas

If you only look at buildings, there seems to be no similarity between North American suburbia and Soviet suburbs.

Typical Soviet suburban apartment bloc

Typical older single-family home of US suburbs

However, even if the Soviet example is very dense, very tall and is multi-family housing, that alone doesn't make it an urban form of development. In fact, the Soviet example is an accomplished case of "tower in the park", Soviet suburbs are often full of greenery with blocs facing trees rather than each other. Just like the detached single-family homes of North America are separated by distance and often use trees to isolate themselves from other buildings and the street.

Both the single-family home of North American suburbs and the apartment blocs of Soviet suburbs are designed to be isolated, to provide a feeling of being close to nature, not to a city. In order to achieve that effect, they use green buffer spaces next to the building on its lot so that other buildings are reasonably far away. In fact, both house and apartment building share the same basic design of a building in the middle of a lot, kept at distance from other buildings:

Basic design of a typical US SFD home

Basic design of a Soviet apartment building

In fact, take a typical villa-type SFD, stretch the lot to make it bigger then build one big building that is essentially homes built side-by-side and one over the other, and you have the Soviet apartment building. In both cases, some kind of isolation is the result, as the units over the ground floor are effectively isolated from any activity on the street. As opposed to single-family homes built with only small setbacks and low-rise apartments with balconies built next to the street, which are less isolated from the street.

Green buffers are used to destroy the urban fabric, meaning the appearance of a dominance of built areas in cities, of buildings forming a coherent whole, enclosing the street and public areas (bringing buildings in contact with the street). By creating these gaps between buildings and filling them with greenery, the goal is to make "natural" landscape dominant, as if one was walking in a park or a forest, not in a city.

Note that this use of green buffers isn't an efficient use of space, not at all. In the case of SFD homes, it represents a huge waste of space that reduces density to a minimum and forces all trips to be motorized. Only mass motorization and the subsidization of high-speed roadways can allow such waste of useful land to go on. And indeed, US suburbs MANDATE that waste. Residents and pro-sprawl planners react with holy terror when the rules that impose green buffers (mandatory setbacks, minimum lot sizes, etc...) are questioned, because they know that without them, many lot owners would seek to make the green buffers productive by building on it, and it would raise the value of land, making the big estates they like more expensive.

In the case of the USSR, I think it goes without saying that this waste of land was also mandated by the government. However, as the USSR was much poorer and planners knew that they would need to rely on walking and transit to move around their population (another nail in the coffin of the canard that cars are cheaper than transit), they still insisted on density, resulting in very tall buildings full of small housing units. That way, they could match the older, dense neighborhoods while maintaining the green buffers. But while they managed to salvage spatial efficiency by doing so, they sacrificed housing affordability as tall buildings are more expensive to build, even the cheap, mass-produced stuff they built. To compensate, they made the housing really, really cramped. If your housing costs twice more per square foot to build, just build units twice as small, right?

It seems to me that everywhere green buffers are abundant, it has been mandated by government in some way. Huge setbacks and distances between buildings is simply not an economically efficient use of space, it is wasteful, so the only way to make sure it remains frequent is to require it.

What does a city that doesn't mandate green buffers and allows individuals to do what they want with their property looks like? Look to Asia for the answer (but not China, which is also planned like the USSR, even if it's less "tower in the park"-y in some places). People are probably getting tired of me bringing up Japan, so here are:

South Korea...

...Thailand...

...and Taiwan

You can also look at old European villages, which have a lot of similarity with Asia. In any case, these loosely regulated cities are completely different from both North American suburb and Soviet suburbs. They have strong urban fabric and could even be called buffer-less cities. Motivated by economic reasoning, they have created dense cities where buildings are built very close to one another, which only rise to the skies when the demand for it is actually there.

Conclusion

So I hope that I have made a convincing argument that North American and Soviet suburbs actually both originate from modernism that rejected traditional cities and wished to tear apart the urban fabric, using green buffers to isolate buildings and people, and try to create the impression of living in a park or a forest rather than in a city. In both cases, the government used different tools to impose the vision of their elites on their population, often until the population just figured this was how things are and always will be. So they are two flavors of the same idea, not two diametrically opposed ideas, and the differences there are were largely dictated by transport needs and wealth level.

I'm not saying that such suburbs are terrible and should be banned. Some people do crave the isolation they bring about. I do not resent their choices. However, I don't think that these preferences should be imposed on people nor subsidized by having everyone pay for the transport infrastructure this kind of development requires to be viable. The idea that North American suburbs emerged organically and represent consumer preferences perfectly also needs to be confronted. It is incorrect, it is a myth, and the fear of development deregulation by promoters of sprawl shows that even they acknowledge that without these regulations imposing sprawl and the subsidies distorting price signals, a lot of people would opt out of sprawl.