Planning: Block Sizes for Small Lots

NB: I believe this topic has been discussed much better many times elsewhere on the net and in print.  I am writing simply to clarify my own thoughts.  I apologize for the primitive graphics.

In a previous post I discussed block sizes for lots that are small enough that single-family detached houses - the kind of dwellings found in most suburbs and many older neighborhoods - stop making sense.  That happens at about 30' in lot width.  Below that figure, attached houses become the rational choice because side setbacks become too small to be anything other than a walkway, while at the same time reducing the width of the building so much that floor plans become inefficient.  Some jurisdictions allow detached houses to be built with essentially zero setbacks on two sides, but that is unusual.  In most locations, houses on narrow lots are attached on both sides, and are called row houses or town houses depending on their context.

Row houses can be built with front garages, rear garages accessed from alleys, private parking lots (almost always in suburban planned communities), or no off-street parking at all.  Front garages in row houses have the same problems as in narrow detached homes - unpleasant appearance, pedestrian-vehicle conflicts, and curb cuts.  In higher density areas, having rear garages or not having off-street parking at all are much better options.

Here I have depicted 24' wide row houses with rear garages.  The overall floor area is a little smaller than with the detached and duplex homes previously discussed, which is not unusual for urban areas where space is at a premium.  The back yard has shrunk significantly due to the reduction in width.  While still spacious by the standards of many countries, in America it would probably be considered by many to be too small.  Increasing the block depth would alleviate that problem somewhat.

When the block depth is changed, the block width should be re-examined.  Three blocks of 300' by 900' make a square that works at lower densities, but at higher densities, the degree to which longer blocks impair walkability becomes important.  Also, while there is no rule that requires blocks align when their orientation is changed, in the abstract doing so makes sense.  Shifting the block size to 320' by 640' would add 10' to each back yard while increasing the walkability, and still forming a square.  However, doing so would lower taxability due to the additional roadway area.  The alley present in this depiction also adds infrastructure that would need to be supported, though at a lower standard.

For American expectations, a 16' wide lot is about the smallest that can be created.  In other countries that have row-type homes, such as The Netherlands, lot widths of 14' or even 12' can be found.  Reducing the lot to 16' would actually decrease density over a 20' wide lot - provided the building remains only 2 stories high - due to the dimensions of the interior space.  Given American expectations and building technologies, only 2 bedrooms can be built in a 16' wide envelope - without resorting to very narrow exposures, which have fallen out of favor since the early 1900s.  Naturally, building higher would allow for more bedrooms.

	24' Duplex	24' Row House	24' RH, deep block	20' RH, deep block	16' RH, deep block
Gross length	900	900	640	640	640
Gross depth	300	300	320	320	320
ROW width	60	60	60	60	60
Net length	840	840	580	580	580
Net depth	240	240	260	260	260
Lot width	30	24	24	20	16
Lot depth	110	110	120	120	120
Lots per block	56	70	48	58	72
Parking – private	2	2	2	1	1
Parking – street	0.75	0.6	0.6	0.5	0.4
Driveway or alley	300	240	240	200	160
Pct. paved	8.33%	8.33%	7.69%	7.69%	7.69%
Back yard	960	768	1008	840	672
Pct. back yard	26.67%	26.67%	32.31%	32.31%	32.31%
ROW per unit	42.9	34.3	40.0	33.1	26.7
Density per block	23,129	28,911	26,136	31,581	29,403

Note: The density shown here is persons per square mile for the block itself.  Overall density as a whole would for a neighborhood of such blocks be much lower, since additional area might be devoted to such uses as larger roadways, parks, waterways, schools, libraries, places of worship, retail and service establishments, offices, hospitals, warehouses, and factories.

Some urban planners and urbanists criticize the long, narrow lots that are used in row house developments in older areas of American cities for being inefficient.  In a future post I will look at other high-density fee-simple lot configurations.

Planning: Parking and Garages

NB: I believe this topic has been discussed much better many times elsewhere on the net and in print.  I am writing simply to clarify my own thoughts.  I apologize for the primitive graphics.

Parking for personal vehicles is the bane of urban planners across the world.  The storage of these large, heavy items takes up a lot of space that can't be used for much else, even when the vehicles are elsewhere.  The surface of parking areas allows for little to no vegetation, depending on the type of material used.  Hard surfaces increases storm runoff, which slows the recharge of aquifers and raises the risk of flash flooding.  But people want cars for many reasons, and thus people want parking.

Personal vehicles are usually the first or second most expensive item a person or family purchases, depending on whether they are homeowners.  Given the amount of money at stake, the decision by many to store a vehicle under a roof is unsurprising.  Under protection, a vehicle will be dry most of the time, reducing corrosion.  A vehicle is also protected from weather damage due to storms, and from deterioration caused ultraviolet radiation.  Storing a vehicle inside also reduces the chance of it being stolen, vandalized, or damaged by a careless driver.  Trees cannot drop sap and birds cannot defecate on a vehicle under a roof.

Parking inside a structure makes getting in and out of the vehicle during inclement weather easier.  It also makes initial operation of the vehicle more pleasant, as vehicle will be cooler in sunny climates, and free of ice and snow in northern climates.  As more vehicles become electrified, having a convenient place to charge the vehicle without the risk of it being disconnected and the charging equipment stolen will be demanded by many people

Storing a vehicle inside is not without risk.  Vehicles can catch on fire, or leak unhealthy liquids.  And it can be expensive to create a separate structure or expand the main structure to accommodate vehicles.  A typical two-car garage is about 500 sq. ft., or from about 1/3 to 1/5 of the space in the living quarters in a typical single-family detached home.  In most cases, the amount of money saved by housing a vehicle in a structure will be less than the cost of the structure.  That is why a great many vehicles are parked outside on driveways.  Other vehicles spend most of their time in private parking lots, or parked on public rights-of-way.

Street parking is problematic for a number of reasons.  In many cases it is not priced directly, meaning there is no hourly, daily, monthly, or yearly charge paid by driver to park the vehicle which reflects the cost of the space.  Instead, the cost of building and maintaining the area on the street comes from taxes and fees.  Thus the incentive is for drivers to use street parking - especially in denser areas where most homes do not have provision for off-street parking - without any concern for how it affects the area as a whole.  Street parking also uses up large portions of the public right-of-way.  In historic areas, that can mean limiting sidewalk width to the bare minimum in order to accommodate empty, non-moving vehicles.  In newer areas, it means reducing the amount of taxable land and increasing the amount of hardscape.

The obvious response to those problems is to limit the demand, which is done in a number of ways.  Some jurisdictions require permits prior to a vehicle being street parked.  The permits usually come with a nominal fee, but the demand control is mostly accomplished by limiting their number.  Another way demand is limited is through metering.  Charging a sufficiently high price for a spot encourages turnover, which allows drivers to find spaces close to the location they wish to visit.  This is important for business establishments that depend on short (1/2 to 2 hour) in-person visits.  Often these metered spots revert to free parking overnight, and the area where they are install is always limited.  The technology used for metering has changed over the years, moving from mechanical coin-operated meters for individual spots to computerized pay-and-display machines for a large number of spots, but the purpose remains the same.

Another way jurisdictions limit demand for street parking is through mandating space for parking be set aside on private lots during building construction.  These parking minimums are controversial because they can greatly increase the price of a home and cause a spiral of reduced density and increased vehicle travel, resulting in the demand for more parking itself.  The minimums are often arbitrarily determined, forcing developers to overbuild parking in many circumstances.  Some jurisdictions have moved away from these standards, and have seen more housing built in downtown areas.

In stark contrast to American practice, Japan has implemented policies of neither requiring parking minimums nor providing for on-street parking in residential areas.  Any vehicle registered in Japan must have a documented place to park.  To catch vehicle owners that are dishonest about having a spot, many Japanese jurisdictions ban all on-street parking overnight, including in metered spots, though it isn't fully enforced until about 3AM.

While the goal of reducing sprawl is a worthwhile goal, parking still needs to be accommodated for the foreseeable future.  The best way forward is to decouple it from housing as much as possible in urban areas, reduce parking minimums wherever possible, and price public parking appropriately.

Planning: Block Sizes for Medium Lots with Alleys

NB: I believe this topic has been discussed much better many times elsewhere on the net and in print.  I am writing simply to clarify my own thoughts.  I apologize for the primitive graphics.

In a previous post I discussed the block size for lots that are of the scale found in older neighborhoods of detached houses.  An important conclusion is that by 40' wide, both front garages and curb cuts become a big issue.  One way to resolve the tension between the demand for private parking and curb cuts is to install an alley along the center of blocks.  (Alleys have a bad reputation as well as some technical issues that I will address in another post.)  Access to the rear of lots allows parking to occur there, and many homeowners choose to build garages on their property.

As you can see, the installation of an alley allows the entire front width of the house to be open, and eliminates the need for each lot to have a long, narrow driveway.  But it does increase the amount of hard area allocated to each lot over the short-driveway snout house described in the previous post.

	40' w/ short driveway	40' w/ rear garage	40' w/ alley	30' w/ alley	30' duplex w/ alley
Gross length	900	900	900	900	900
Gross depth	300	300	300	300	300
ROW width	60	60	60	60	60
Net length	840	840	840	840	840
Net depth	240	240	240	240	240
Lot width	40	40	40	40	40
Lots per block	42	42	42	56	56
Parking – private	2	7	2	2	2
Parking – street	0.5	0.5	1.0	0.75	0.75
Driveway or alley	297	1355	400	300	300
Pct. paved	6.19%	28.23%	8.33%	8.33%	8.33%
Back yard	2320	1380	1960	840	840
Pct. back yard	48.3%	28.75%	40.8%	23.3%	23.3%
Building separation	12	12	8	6	12

Note: all these houses have approximately the same floor area - not counting garage space, whether within the house or separate.  They are just shaped somewhat differently depending on the configuration.  Also, I have calculated the coverage percentages against a 120' depth even though the legal lot would be only 110' deep.

While adding an alley has clear advantages over front-driveway rear-garage homes, they actually somewhat less efficient in terms of hard area and providing for back yards than short-front-driveway front-garage homes.  Alleys increase the amount of on-street parking, and that parking comes in much larger chunks, meaning that longer vehicles such as moving trucks could be parked without blocking driveway access.  Alternatively, the on-street parking could be eliminated and the area used for bicycle lanes or wider curb lawns.

With a 40' lot width, in think the block length and depth remains workable at 900' by 300' when an alley is added.  The back yard is obviously smaller than with an 80' lot, but it is still a reasonable size even with parking taking a big bite out of it.  But at the next width down, the back yard shrinks substantially because the house becomes deeper (for the same area) and the space beside the garage basically disappears, being so small as to be not be useful for anything but a passageway.  A back yard of 28' by 30' would still be considered plenty in many areas of the world, but an argument could be made for increasing the block depth by 20' or 30', or 10' to 15' for each yard.

At a 30' lot width, another argument can be made that the fundamental form of the house should be changed as well.  So far I have assumed that the homes under discussion are single-family detached houses.  While that form dominates car-oriented suburbs - mostly due to legal reasons - in denser areas other forms start to appear.  These mixed neighborhoods were mostly built before comprehensive zoning became standard practice.  One form is the duplex (of the side-by-side type), or semi-detached house.  It is a fairly straightforward change from the detached house, not requiring a different form of ownership.  The legal structure supporting the party wall is well-established in most jurisdictions.  Sharing a single wall has the advantages of reducing the amount of energy needed to condition the home, and freeing up space for a larger side-yard, while still allowing light to enter on three sides of the building.

In a future post I will examine small lots, on which the rationale for connected forms of housing becomes overwhelming.

Planning: Car-free vs Vehicle-free

NB: I believe this topic has been discussed much better many times elsewhere on the net and in print.  I am writing simply to clarify my own thoughts.  I apologize for the primitive graphics.

The primary goal of many urban planners and other urban advocates is to create walkable cities.  These are or would be places where the vast majority of trips urban residents make in their daily lives are done with a combination of walking, cycling, buses, bus rapid transit, trolleys, trams, light rail, subways, regional rail, and "micro-mobility."  The latter is an umbrella term for short-range transportation devices that operate at speeds above walking but below cycling.  They include e-scooters, e-skateboards, and human-powered equivalents.  The combination of modes would enable people in cities to live without cars, or at least without using cars on a regular basis.

Some urbanists take the idea of living car-free even further, and imagine cities that are largely vehicle-free.  The built form they desire would be so compact that most public rights-of-way would be scaled to pedestrians, cyclists, and micro-mobility users.  Vehicles would only be occasional intruders on most streets, and some rights-of-way would be so small that no normal four-wheeled vehicle could ever enter.  I disagree with that goal, and believe the idea of reducing streets to sizes that made sense when all vehicles were either human-powered or animal-drawn is misguided.

There is no doubt that human-scaled cities are highly enjoyable.  Pre-automobile areas in cities like Venice, Sienna, Canterbury, Lisbon, etc, are both wonderful places to visit and popular places to live.  But they are also inconvenient places to live, and are often dominated by tourists and younger people.  Making cities vehicle-free would just exacerbate the inconveniences.

There are a large number of business and public services that have a reason to regularly send vehicles into high-density urban areas and park close to residences or neighborhood businesses for varying amounts of time.  Below are some examples.

Type of service	Example
Personal deliveries	meals, groceries, medical supplies, mail, packages, laundry, dry cleaning, furniture
Business deliveries	produce, dairy, meat, baked goods, beverages, dry goods, office supplies, general retail, documents, medical samples
Public services	police, fire department, emergency medical service, public works
Private services	plumbers, electricians, HVAC technicians, appliance repairpersons, movers, cleaners
Transportation	taxis, shuttles, public buses, school buses, paratransit

The vast majority of those services are best provided with vehicles.  For instance, plumbers that come to repair a sink will be more likely to complete the job on the first visit if they have the necessary parts in their truck instead of having to drive back to their warehouse if they don't have the item needed.  And they will complete them faster if they can park close to the residence and can run down quickly to get necessary supplies rather than walking a block or two to the spot they happened to find after circling for 15 minutes.  Public services such as fire departments usually have an exemption to double park when attending to emergencies, but they are not always on deployed for an emergency.  Many fire departments engage in inspections to see if business meet fire safety regulations, and should not block regular travel lanes when they do so.  Produce distributors visit many of their customers daily, due to how quickly the merchandise spoils, and do so in large, refrigerated vehicles that drive considerable distances from the warehouses where they are based.  Having to make more trips due to reduced vehicle size would increase the cost of food and meals.  And so on.

Transit buses are another type of vehicle that should not be discouraged or banned.  Rail-based transit has a role to play in many cities, but the infrastructure is more expensive to construct.  Buses have a lower up-front cost and can be adjusted to match ridership demand more easily.  Bus routes can be designed to intersect and feed rail transit, or to provide another layer of longer-distance transit for where rail transit doesn't reach.  Buses work better when they can keep moving at a reasonable speed.  This means limiting stops, and limiting the number of interruptions to travel.  Interruptions can be caused by traffic, and by stopped vehicles which buses have to maneuver around, or even wait for until they are moved.

The types of vehicles that are most likely to block a bus are commercial and public service vehicles, of course.  They double-park because curbside spots are usually taken up by personal vehicles that are parked for extended periods.  The specifics vary from city to city, but in all, some personal vehicles are in metered spots in choice locations in front of commercial establishments, but many are in un-metered spots on mostly residential streets.  By reducing the number of spots available available for personal vehicles, more commercial and public service vehicles could park out of the way of traffic, and specifically buses.

Implementing a car-unfriendly but vehicle-accommodating streets in already dense areas would require several relatively easy - though potentially unpopular - steps.  One would be to plate register or tag each class of vehicle - government, commercial, and personal - separately, so they could be easily identified.  Another would be to determine if areas need to be metered for personal vehicles, and when.  Another would be to enforce parking regulations for the un-metered sections.  Commercial vehicles would be banned overnight and allowed during the day (5AM-7PM), while personal vehicles would be allowed at night (5PM-5AM).  After that, some fine tuning would be needed to see if there are some classes of vehicles that are evading the general goal, or if metered areas need to be resized.

There could be other sets of policies that would achieve the same goal of allowing for commercial and public vehicles easier parking in dense urban areas.  But the main point is that planners should recognize that they exist and are a part of modern urban life.  The fantasy of everyone living in a medieval-scale city is not going to come true, and vehicles need to be accommodated and managed.

Planning: Block Sizes for Medium Lots

NB: I believe this topic has been discussed much better many times elsewhere on the net and in print.  I am writing simply to clarify my own thoughts.  I apologize for the primitive graphics.

In a previous post I discussed the block size for a lot that is at the large end of the spectrum for American urban areas.  I concluded that the lot worked well within the block size I had selected.  But what about smaller lots, closer to what can be found in older sections of American cities?

This configuration, with lots 60' wide, is basically the same as with 80' lots.  The density increases by about 25%, but it is still car-oriented.  Each lot has an ample back yard, and plenty of room for off-street parking.  There is no obvious reason to increase or decrease the block depth, and block length should be at least 900' to keep taxability high.

The next step down in lot size is 40', increasing the density again, this time by 33%.  In this configuration, the appearance of the house from the street is dominated by the garages.  This form has been dubbed the "snout house."

Here I have depicted a 28' wide house with both single and double garages.  In the latter case, the house is barely wide enough to allow for a human-sized front door next to the garage.  And in both examples, the front yard is dominated by the hard surface of the driveway.  The back yard shrinks considerably on these lots as the footprint of the home is roughly the same size as on an 80' lot.  However, if the outdoor parking in front of the garage is discarded, it is possible to bring the home forward in order to expand the back yard.

But this adjustment just brings unfriendly garage doors closer to the street, giving the public space an appearance similar to that of an alley.  Another possibility is to move the garages out of the mass of the home and into the back yard.

This alteration would improve the appearance of the home and street, but the yard would have vastly more hard surface, increasing the problems of storm runoff and the urban heat island.  And it would change what activities that could be pursued in the back yard. 

	80' w/ long driveway	60' w/ long driveway	40' w/ long driveway	40' w/ short driveway	40' w/ rear garage
Gross length	900	900	900	900	900
Gross depth	300	300	300	300	300
ROW width	60	60	60	60	60
Net length	840	840	840	840	840
Net depth	240	240	240	240	240
Lot width	80	60	40	40	40
Lots per block	22	28	42	42	42
Parking – private	4	4	4	2	7
Parking – street	1.5	1	0.5	0.5	0.5
Driveway	610	610	549	297	1355
Pct. paved	6.35%	8.47%	11.44%	6.19%	28.23%
Back yard	5360	3360	1680	2320	1380
Pct. back yard	74.44%	46.67%	23.33%	32.22%	28.75%

More importantly, the number of driveways and curb cuts remains the same in all of the 40' lot configurations, each of which increase the chances of vehicle-pedestrian conflict, and reduces the amount of on-street parking.  40' wide seems to be the lower limit for front driveway lots.  The block length remains acceptable as the density is still below general walkability.  The lots would be larger if depth was increased, but there's no particular reason to think the lots are overly small, other than personal preference.  I will look at a different block layout in a future post.

Planning: Right-of-ways and Roadways

NB: I believe this topic has been discussed much better many times elsewhere on the net and in print.  I am writing simply to clarify my own thoughts.  I apologize for the primitive graphics

One of the terms I used in my previous post on planning was 'right-of-way' (ROW), which is the public area used for circulation between various private and public properties.  Right-of-way implicitly means publicly-owned, but there are some cases where privately-owned streets function in a similar way.  Those are usually behind gates that exclude most of the public, and are largely confined to car-oriented low-density suburbs.

Rights-of-way vary greatly in size, from the walkways of a traditional Greek island town such as Mykonos to grand boulevards of a capital city such as Paris.  Walkways can be as narrow as a few feet, barely leaving room for two people to pass, but major boulevards can be hundreds of feet wide between the surrounding properties.  Narrow rights-of-way do not have the space to segregate traffic into different lanes - which would be pointless for a footpath to begin with - but wide ones always have multiple divisions, usually including areas for motor vehicles, and pedestrians.  They can also include other linear elements such as medians, curb lawns, drop-off zones, bicycle lanes, bus lanes, parking lanes, tramways, and service roads.

Decisions about the width and contents of a right-of-way are important factors in determining an area's visual character and walkability.  Naturally, a right-of-way needs to reflect the amount of traffic it is expected to receive, which is in part determined by the density of development along it. And in for the foreseeable future, most rights-of-way will include roadways as their main element.  But those roadways should not necessarily be the dominant or overwhelming element if the street is to have any kind of walkability.  A limited-access divided highway is an example of a right-of-way that has absolutely no provision for anything but motor vehicles, though they are uncommon in terms of number.

In the post the previous post I specified a 60' ROW to surround the block size I discussed.  As with the block, it was chosen as a reasonable starting point for a low-density area.  That width allows for a 28' roadway bordered by relatively generous 10' curb lawns and standard 5' sidewalks on each side.  In suburban situations an additional 1' between the sidewalk and the private lots is often public property, but not used for anything in particular.  The narrow unimproved area is treated as part of residences' yards for maintenance and landscaping purposes.  A 5' sidewalk allows for two people to easily pass without touching, and two people to walk abreast without stepping off the pavement.  A 28' roadway allows for parking on one side and vehicular movement in both directions.  Cyclists share travel lanes with motor vehicles, which are usually unmarked.

Now that is only one of a possible number of configurations, but is typical for low-to-medium density suburbs.  But as with any decision, there are trade-offs.

	Square	Square	Mildly Rectangular	Mildly Rectangular
Gross Length	300	300	600	600
Gross Depth	300	300	300	300
ROW width	60	50	60	50
Net Length	240	250	540	550
Net Depth	240	250	240	250
Taxable area	64.0%	69.4%	72.0%	76.4%
Increase	n/a	8.5%	n/a	6.1%

Reducing the ROW width just by 10' results in a significant increase in taxable area.  The reduced ROW would require taking space from one of its element, however.  The sidewalk is already at the American minimum, leaving the curb lawn and roadway as possible sources.  By eliminating parking, the roadway could be reduced to 22' and the curb lawns would remain sizeable at 8'.  Or the curb lawns could be reduced to 5' and the parking could remain.  The arrangement does not have to be symmetrical, of course, and another option would be to have a wide curb lawn measuring 10' on one side, and parking opposite.  Other configurations of a 50' ROW are possible.

The inclusion and sizing of any element in a right-of-way reflects a combination of factors, including cultural values, citizen demand, the typical sizes of vehicles, climate, and cost, which is always involved.  For instance, large commercial vehicles in the the United States are typically 102" wide, filling most of a 10' lane.  Winter storms in Vermont can leave 12-24" of snow, which when plowed from the streets ends up on the sidewalk if the curb lawn is too narrow.  In Tokyo, most residential streets don't have sidewalks because residents are used to sharing narrow streets between pedestrians and vehicles.  And in large portions of low-income countries, there is no infrastructure development whatsoever, due to indifference, corruption, poverty, or all three.

While, arguably, there is no absolute right and wrong here, the decisions about the design of rights-of-way have major influences on the built and natural environment.  Designers should take into consideration not only local practices and expectations, but also global experiences and long-term considerations when working on a new planning document.

Planning: Block Sizes for Larger Lots

NB: I believe this topic has been discussed much better many times elsewhere on the net and in print.  I am writing simply to clarify my own thoughts.  I apologize for the primitive graphics.

In my previous post, I provided some calculations to show that rectangular blocks are more taxable than square blocks, and suggested that is why many planners have decided to trade higher taxability for walkability in many cities.  I used unitless dimensions, and I did not get into the details of how specific block lengths and depths might work.  But the details are important, and so I will begin to examine them below.

While I have not decided on an ideal block size, I have picked an overall block size of 300' by 300' with a 60' right-of-way (ROW) on all sides as a reasonable starting point.  (The ROW is split between blocks, so only 30' is taken from each side.)  Those dimensions result in a taxable area of 240' by 240', which happens to be easily divided into many lot widths - 80', 60', 40', 30', 24', 20', and 16'.  With houses on both sides, lot depth is 120' without an alley present.  And 80' is not large by suburban standards, but is a good starting point for exploring walkability and block size.  What does a small block with 80' lots look like?

That is a lot of hard surface area for very few houses.  With a 30' roadway, there would be about 1080 linear feet of sidewalk, or 180' per lot.  If the cost to replace the sidewalk is $200 per linear foot, a major sidewalk replacement program would burden each lot by $36,000.  Of course, that does not happen very often, because estimates of the lifespan of a concrete sidewalk range from about 25 to 80 years.  Roadways have to be repaved more often in most areas, and that can cost about a $1M per lane mile.  With a 300x300 block, repaving could cost about $60,000 per lot.  And most of the paving is doing nothing but providing free parking.  With a 30' roadway and parking on one side, there are about 1.5 spaces per lot of street parking when the side streets are included.  That is in addition to the 2 spaces in each garage and 2 spaces on each driveway.  Clearly, with an 80' lot width, it makes sense to go to larger blocks.

This version looks a lot like a typical moderate-density suburban block, probably because developers are in the business of selling houses, not streets.  (Note that I have included 60' lots as needed in the following calculations because 80' does not divide into some of the lengths evenly.  The general point of the calculations remains.)  In this configuration, each lot has to support about 104' of sidewalk and 109' of street, down from 180' and 200'.  Each lot gets only about 0.9 spaces of on-street parking, or about 0.7 if the 30' cross streets are striped for bike lanes.  Below are the calculations for the two sizes pictured, as well as some others.

	Square	Mildly Rectangular	Seriously Rectangular	Extremely Rectangular	Excessively Rectangular
Gross Length	300	600	900	1200	2400
Gross Depth	300	300	300	300	300
ROW width	60	60	60	60	60
Net Length	240	540	840	1140	2340
Net Depth	240	240	240	240	240
Lots per block	6	14	22	30	60
Sidewalk	180	120	104	96	88
Street	200	129	109	100	90

Developers sometimes build blocks that are around 2400' long, but they are rarely straight, in order to break up the monotony of a street of basically similar houses, and also to conform to local topography when necessary.  In the other direction, the lot depth in a 240' block is sufficient.  A 40' deep house set back 20' from the road would have a 60' deep back yard, or half of the total lot.  That enough room to put at a deck, a pool, and a play set, which are common features of American back yards.

But any neighborhood with lots of these dimensions would not be walkable.  It would be physically safe to circulate on foot, as the traffic density would be low, and the number of street crossings would also be low for the larger blocks.  It could be moderately pleasant if the curb lawns are well-planted with trees.  But it would still be a typical suburban area with little visible activity and nothing to visit nearby.  At the density provided for by 80' lots, it would likely be over a mile from most homes to the nearest shopping center.  Most people would end up driving that distance, leaving walking primarily to children and those who want the health benefits of walking.

Planning: Square or Rectangular Blocks

NB: I believe this topic has been discussed much better many times elsewhere on the net and in print.  I am writing simply to clarify my own thoughts.

In my previous post on planning, I looked briefly at the issue of block size.  Before I pursue that question further, I want to examine why many urban street networks have rectangular blocks, often in a rough 2:1 ratio of length to depth.  Of the grids I mentioned before, Manhattan, the Little Village neighborhood of Chicago, Stockholm, and Turin have blocks that are mostly rectangular.  Square blocks dominate Barcelona, Madrid, Portland, and downtown Chicago.  Many more examples of both tendencies abound.

So if, as I explained in the previous post, smaller block sizes contribute to the quality of walkability, why would planners choose rectangular blocks?  I believe the main driver is infrastructure efficiency, or taxability.  Calculations illustrate the problem quickly.

	Square	Mildly Rectangular	Severely Rectangular	Extremely Rectangular	Large Square
Gross Length	300	600	900	1200	600
Gross Depth	300	300	300	300	600
ROW width	60	60	60	60	60
Net Length	240	540	840	1140	540
Net Depth	240	240	240	240	540
Taxable area	64.0%	72.0%	74.7%	76.0%	81.0%
Increase over previous (baseline for large square)	n/a	12.5%	3.7%	1.8%	26.6%

The increase in the taxable area is most likely why planners choose to make at least part of planned cities rectangular grids instead of Cartesian grids.  Most planners have used a ratio close to the 2:1 proportions shown in the second column, because the returns on higher differences in dimensions decrease.  In addition, if the depth of a rectangular block remains reasonable (note that I did not specify units in the table), unlike with a larger, less walkable square block, lots remain useful without alley access, and can be developed into fee-simple properties up to moderate densities.  The combination of taxability, walkability, and practicality is why so many cities have rectangular grids for at least part of their street network.  However, there are trade-offs in any decision, so planners should continue to respond to local conditions when laying out a particular block or set of blocks.

Planning: Ideal Block Size

NB: I believe this topic has been discussed much better many times elsewhere on the net and in print.  I am writing simply to clarify my own thoughts.

One of the perennial questions in urban design for those who get caught up in the details is the question of city block size.  Since the organic texture of older cities such as Rome, Paris, or London isn't easy to prescribe, people instead focus their interest on the best layout of a planned city.  And the size of an individual block often becomes a major decision.  The answer is, of course, there is no perfect size, as there are trade-offs in any complex decision.  With respect to block size, the primary trade-off is between walkability and taxability.  The later really isn't a word, so a better term would be infrastructure efficiency.

The most basic infrastructure element of any community is the transportation corridor between the various properties that make up a community, whether they are residences, retailers, offices, schools, hospitals, warehouses, factories, or other less common establishments.  In developed countries, most of the transportation corridors are dedicated to motor vehicle traffic.  In American practice, the corridors are called streets or roads, depending on the context.  Streets in urban areas usually consist of space for motor vehicles to circulate, flanked by space for pedestrians.  They usually include sections for parking and for vegetation, and sometimes include dedicated lanes for cycling.  The entire publicly-owned area between the other properties is referred to as the right-of-way. Roads in rural regions are generally built solely to accommodate vehicles.  Suburban regions see a mix of street elements and can be called either roads or streets.  Fancier names such as avenue and boulevard are usually applied to major arterials in cities, and highways to major inter-city roads.

Any transportation corridor that is more advanced than a dirt path must be paid for somehow.  Usually, that is accomplished through taxes.  In America, property developers often build or substantially upgrade the local streets or roads that pass in front of most residences, and then property taxes pay for ongoing maintenance.  Excise and income taxes pay for new regional and national roads, and for their ongoing maintenance.  The exact division of funding is determined by various agreements, the details of which aren't all that important here.

The efficiency element comes from the ratio of private, taxable space to public, tax-supported space.  For instance, a 200' by 200' block (measured from the centerline of the street) with a 100' right-of-way (ROW) on each side leaves only a 100' by 100' plot of land which can be taxed.  That is only 25% (100,000 square feet) of the entire block (400,000sf).  Such a configuration would result in a lot of infrastructure for each property to support, increasing the taxes on each property.  A more realistic ROW of 50' surrounding the same block gives a ratio of about 56%.  A 300' square block bounded by a 60' ROW yields 64%, and a 600' square block with a 80' ROW yields 75%.

The other side of the trade-off is walkability.  For the purposes of this discussion I am going to leave aside the debate over the value of walkability itself.  But assuming it is a desirable quality doesn't do much to define it, of course.  What makes an area walkable is a topic covered in a tremendous amount of writing by architects and urban planners.  The elements that are often cited as contributing to the quality walkability include: the width of the roadway (if present), sidewalk (if separate), and bikeway (if present); the presence and specifics of vegetation; the presence and specifics of street furniture and other physical elements; the number of housing units, quantity of office space, and presence or absence of retail establishments; the size and aesthetic qualities of the surrounding buildings; and the size of a block.

Basically, big blocks are a chore to walk along and between.  Explaining the unpleasantness of between blocks is easy - fewer streets means each street has to handle more traffic, increasing its width and the danger to pedestrians who cross it.  The unpleasantness of along comes from the traffic of adjacent streets, and the fewer number of paths to a point.  Cars - even electric cars - are noisy, and the more there are and the faster they go, the less pleasant it is for pedestrians nearby.  If the cars are directly adjacent to the sidewalk, that can make pedestrians feel unsafe.  Fewer streets also reduces the number of buildings, establishments, and other points of interest that a pedestrian experiences on a trip, making it less interesting.  And finally, big blocks reduce the number of paths between two points, leaving a pedestrian fewer opportunities to shape a journey to pass things that are pleasing, or to combine different elements in a new way.

To get back answering the question in the title of the post, one way would be to look at existing examples.  For instance, Manhattan is famously gridded, with the pattern established at 14th St. dominating the plan all the way up to the northern end.  Blocks there are mostly 264' in depth, but vary in length between 500' and 900'.  Many people have commented that the latter number is too large.  However, Manhattan has a much more linear shape than most urban centers, which are not so tightly bounded by water, and the long sides of the blocks are perpendicular to the primary direction of travel.   Chicago has a number of grid sizes, including 400' by 400' in The Loop, and 330' by 660' in the Little Village neighborhood.  The planning of Phoenix is mostly dominated by car-oriented superblocks of 5280' square, and though they are subdivided finely close to downtown, very little is walkable.  Barcelona has a grid size of approximately 440' by 440', and gridded portions of Madrid are similar.  In Stockholm, blocks vary considerably, but many are about 330' by 560'.  Turin, which has a core originally laid out by the Romans, also has a range of block sizes, with some as small as 180' by 280'.  Grids in the Buenos Aires metropolis have several different orientations, but most blocks are about 440' by 440'.

Since that way provides no clear answer, only a range of values that isn't surprising, I will continue my exploration further in subsequent posts.

Ending the Forever Stupidity

There's just no way this isn't a positive development:

The departure from Bagram follows President Biden’s decision in April to withdraw all U.S. troops from Afghanistan by September, ending what he and other critics have called a “forever war.” As the Taliban launched a bloody offensive and encircled numerous provincial capitals, defense leaders last month briefly considered slowing the military’s departure from the air base, officials said, speaking on the condition of anonymity because of the sensitivity of the issue. The Biden administration ultimately decided to continue the withdrawal.

The end of a significant military presence will be bad for many Afghans.  There's no point in pretending otherwise.  But, ultimately, America can't fix Afghanistan, and there is no reason to continue failing at the task, which never should have been undertaken in the first place.  America should have withdrawn long ago, but didn't due mostly to internal reasons.

A sure sign of a failing state is the inability to adapt to new information.  I am cheered by Biden's willingness to adapt.

Already there has been a dramatic reduction of drone attacks and other types of airstrikes, which once reached thousands a year. “The [United States] appears to be in a holding pattern in most conflict theaters that it still has a presence in—with no reported strikes in Yemen, Libya, Pakistan, or Somalia since Biden took office. U.S. strikes are continuing in Afghanistan, Iraq, and Syria—though at historically low rates,” said Chris Woods of the London-based Airwars monitoring organization, considered perhaps the most reliable tracker of U.S. airstrikes around the world.

Even in the early 2000s it was clear drone strikes were overused, and again in retrospect it was bad policy to use them outside of the immediate theater of battle.

The White House team is also seeking a broader reorientation toward what the president has called “the battles for the next 20 years, not the last 20,” including climate change, the threat from China, COVID-19-type pandemics, and America’s economic and social problems at home.

Finally, some foreign policy that makes sense.  There will be pushback from the usual suspects - the DoD, the MIC, the Blob, warmongers, deeply concerned centrists, and Repuke opportunists.  But if Biden continues to push foreign policy in the directions outlined, American will be better off in the short term and long term.