Category: Analysis

Anything that I have tested empirically, or explain with detailed calculations, or just generally bother to get all the facts straight.

Post #593: Expedient masks, part 1, background.

Source:  Amazon.com

 

The bottom line of this posting is that, yes, home made masks work to block much of your potential for transmitting disease to others.  Wear a real medical mask if you own one.  Buy (and potentially improve) a non-medical one if you don’t.  Or make one from scratch.  Even paper towels have some efficacy in filtering the air.

This post is really just background.  If you already know that you need to wear a mask, there is no need to read this.  Next post will be about what you can still buy, for now.  Final post will be on making them.

Background

The drumbeat in favor of universal mask use outside the home is getting louder. Some people figured this out sooner than others.  I finally wised up less than a week ago, and did my 3/27/2020 grocery shopping masked.  And every time I enter a public place from now on, I’m wearing a mask.

That said, you can see a summary of the achingly slow progress on this front in this Washington Post article.

So, unless spectacular stupidity triumphs, you will soon have official guidance from the CDC that you ought to wear a mask in public.  I’ve already written down what I would use as the official rules, FWIW (Post #589).  I’ve now posted a comment on the Whole Foods Facebook page, asking them to consider some form of “no mask, no service” policy.

Everybody who is smart, ethical, or both is withholding N95 respirators from the general public.  AKA, the best masks.  Those need to be kept for health care providers.   Here’s Home Depot’s policy.

Executed a "Stop-Sale" on all N95 masks in stores and HomeDepot.com and redirected all shipments to be donated to hospitals, healthcare providers and first responders around the country

I highlight Home Depot because that’s the first place I detected panic buying/hoarding behavior, back in Post #535. Even if they were too late to stop that, they have had the good sense not to restock.

My point is that mask use is coming.  You can’t buy the ones that protect you with some security (if they are properly fitted).  What can you do?  What are your options for an expedient mask?  What is your best expedient mask choice?  Adapt what you have?  Buy?  Buy and modify?  Make from scratch?

From the standpoint of not infecting others, it’s all good, pretty much.  Any mask beats no mask, hands down.  When you talk, and even to a small extent when you breath, you emit tiny droplets (discussed at length in Post #573, Post #585). Droplet transmission of disease is believed to be the primary way in which the infection is spread.  Any sort of substantial cloth barrier over your face will reduce the spread of those droplets significantly, both by catching some, and by reducing the velocity/range of others, as the mask slows the velocity of your breath.  (See wet finger whistle test in Post #589 to prove this to yourself.)

See this reference for a scholarly look at the ability of home-made masks to stop spread of disease.  But please note that they used the wrong cloth (cotton t-shirts) — nobody recommends that.  They concluded that homemade masks aren’t as good as surgical masks, but they are much better than nothing.  I’ll get into that paper in detail, at the end of this posting.

So the only thing to discuss, really, is how you can get some sort of mask, and then, how well can you expect that mask to protect you.  This assumes you are smart enough to do everything the CDC already says, and in addition, minimize your trips to enclosed public spaces, and the time you spend there, on those trips.

While you can buy some type of (e.g.) cloth face mask now, well, by this time we all know the drill.  The supply chain is set up to deliver product only at the rate at which it is used.  As soon as the CDC says “wear a mask of any sort”, it’s a fair bet that what’s currently for sale will get hoovered up.

So, for most of you who don’t have a mask, I’m afraid this is going to turn into a DIY project.  Or, having your neighbors make one for you.

So I thought that what I might do is offer a kind of mask tutorial.  This is mostly by way of helping me get my thoughts together on whether or not I could build a high-quality expedient mask from available materials.  Anybody can make a mask.  The question is, can I make a good mask, in quantity.

This is part 1:  Background.  Part 2 will be, what can you buy (for now) and modify.  Part 3 will be, what can you make from scratch.

Step1:  What are we talking about?  Definition of N95, PM2.5, MERV, HEPA, and so on.

I’m kind of tired of writing, at this point, so this will largely be done without citation as to sources.  I’m just summarizing things here that I have duly cited in earlier posts, mostly. New information will be cited as needed.

Aerosol versus droplet transmission

Micron (micrometer):  One millionth of a meter.  1000 nanometers.  Droplets from a sneeze range from under about one micron to hundreds of microns.

Nanometer: One billionth of a meter. The diameter of an individual coronavirus particle is around 120 nanometers (Wikipedia).  An obsolete term for it is “millimicron” or “millimicrometer”.

Aerosol versus droplet transmission.  Here’s a key distinction.  Conventionally, anything under 5 microns is an “aerosol”, meaning, it will stay suspended in the air and float around on air currents.  See Post #585.  Particles that size are far too small to be seen. When professionals talk about “airborne transmission”, then mean transmission of the disease in this fashion. If you inhale enough of them, from an infected person, and they land in the right place in your respiratory tract, you get infected.

Studies of influenza showed that aerosol particles were quite potent at spreading lower respiratory tract infections.  It takes less total volume of virus to cause an inflection of you aerosolize it, versus leaving it in larger droplets.  The reason is that if you inhale these tiny droplets, they have the ability to penetrate far into the lungs.  (This same ability is what makes very fine particulates from (say) diesel exhaust particularly harmful air pollution).  And, for SARS (currently SARS-CoV-2 aka COVID-19), that’s where this virus wants to be.  So aerosols put the virus directly into its most favorable habitat within the human body.

Sneezing and coughing produce some aerosol-sized droplets.  But, surprising, just breathing produces a few.  Talking produces them at a rate somewhat less than coughing (but you talk a lot more than you cough, so total production can easily be the same, when integrated over time).  The louder you talk, the more aerosols you produce.  And singing is easily the equivalent of coughing, in terms of the rate of aerosol production.

One fact you need to know is that, for aerosols, some people are “superemitters”.  They produce orders-of-magnitude more aerosol than the average person.  And it’s not really all that rare, but I’m not going to stop and look that up right now.  My recollection is that in any group of 100, you are more than likely to find a few.

And so, likely that event that I wrote about — 45 persons of a 60 person choir got COVID-19, after a single carefully-done practice — it’s a very good guess that this was the result of aerosol transmission of disease by an infected superemitter.

That said, I need to be clear here, because this is now a hot topic:  As far as anyone knows, aerosol transmission of this disease is rare outside the hospital setting.  How do they know?  Well, they think they know that because of what they think they know of the epidemiology of it. If aerosol transmission were common, you probably wouldn’t be able to trace cases back and figure out how they got infected.  Because they think they can do that tracing, and they find that most transmission (that they can trace) appears to occur when people are symptomatic (i.e., coughing), they infer that most transmission is, in fact, droplet transmission, not aerosol.

Let us each now solemnly pray to our respective God or Gods that they are correct, and not just kidding themselves.

The situation in a hospital is different, though.  There, you can get instances where the concentration of aerosol particles is high enough, and exposure times are long enough, that people can get sick literally by simply breathing the same air as the patient.  You’ve got a combination of a very sick patient (so, high virus shedding rate), in a small room (so that person can build up high density of aerosol per cubic foot), and you have health care personnel who spend considerable time in that tainted air.

The non-negligible potential for aerosol transmission in that setting is one of the reasons that health care practitioners need N95 masks.  I’ll get to the definition of N95 below.

By contrast, health professionals use the term “droplets” to mean drops larger than 5 microns.  To a greater or lesser degree, these settle out of the atmosphere fairly quickly.  (Or, at least, that’s the conventional wisdom).  But, if you inhale them, or they land on you in the right place (in your mouth, eyes, nose), or they land on a surface that you touch and then touch your face (mouth, eyes, nose), they can infect you.

You produce droplets by sneezing or coughing, but you also produce them by talking.  (And, because we talk a lot more than we cough, arguably, at small droplet sizes, we’re producing more in total by talking.  Which is among the reasons I called for us all to shut up in public spaces.)

The fact that droplets settle pretty quickly is the basis for the 6-foot social distancing rule.  In theory, if somebody coughs from six feet away, the droplets produced won’t hit you.

But social distancing alone is not good enough for the Chinese.  They use masks, both to absorb some of the droplets, and to slow down the velocity with which they are projected away from the source.  And they are absolutely right in doing that.  Which is why US policy is about to change.

Filtration standards and such.

An incredibly helpful and succinct discussion of single-use masks, surgical masks, and N95 respirators, along with considerable other helpful information (e.g., can you wash disposable masks) can be found at Smart Air.  If you want to get up to speed on what’s what, for actual medical supplies, that’s the place to start.

A different guide to the different types of “surgical” masks can be found at Crosstex (.pdf).  The takeaway  from both of these is that just because it looks like a surgical mask does not mean that it filters viruses and droplets like surgical mask.  It may or may not.  And if it were certified to filter like a surgical mask, it would probably not be on sale to the general public.

N95:  A filtration standard meaning that, when new and carefully tested, a mask will stop 95% of very tiny (0.3 micron or 300 nanometer) particles.  Source:  FDA.  Note that, in real life, you don’t actually achieve that because air leaks around the edge of the mask.  That’s why, for protecting the mask user, a properly-fitted mask is important.  For the mask maker, that means you need to construct it so it seals well.

But that’s the primary reason that health care professionals need N95s.  They really need to be able to stop everything, all the droplet sizes, and stop particles down the size of a few viruses stuck together.  That’s why they need those masks more than we do.

N99, P95, P99:  Additional mask standards.  First one filters 99% of particles that size.  The Ps have the indicated filtration, but are good for oily particles as well, where the Ns aren’t (I think of it as P as in paint).

How in the heck do you filter out something that small, and still be able to breathe through the mask?  Mainly, through the miracle of Melt-blown cloth.  This is a nonwoven cloth made from small-diameter plastic fibers fused together.  It is the heart of most common medical masks, including both N95 and true surgical masks.  This is the element in the mask that filters out fine particles.  And, of course, many different types are made, so you can’t just buy melt-blown cloth and assume it’s good enough for a mask.

PM2.5 (particulate matter 2.5 microns) refers to air pollution particles of around 2.5 microns in size.  In essence, PM2.5 is shorthand for all the common air pollutants that are aerosols, i.e., can stay suspended in the air.  Note that, by definition, an N95 mask filters out at least 95% of PM2.5.

PM2.5 mask.  Near as I can tell, this is not a standard.  This just means that the manufacturer claims that the mask was designed to filter out PM2.5.  It’s a mask that claims to filter out (some, all, most?) particles of that size.   Near as I have been able to tell, a) nobody tests those claims, b) a lot of PM2.5 masks and respirators don’t do what they claim (but some do), and c) near as I can tell, these are not approved for use by health care personnel.

Mask versus respirator.  Near as I can tell, anything that is truly designed to seal up against your face, so that air doesn’t leak around the device, is technically a respirator. By contrast, if it’s designed that air likely leaks around the edges and/or the principal purpose of it is to stop fluids, that’s a mask.

That’s why you’ll hear the terms N95 respirator and N95 mask used interchangeably.  Even though the thing looks like a mask, it’s supposed to function like a respirator.  You are supposed to fit the thing to your face so that air leaks are minimized.  Otherwise, really, what’s the point?

Edit:  Single-use mask versus surgical mask.  I didn’t even realize there were standards here, but see this page at Smart Air for a very helpful discussion.  Single-use face masks are typical single-layer thin masks.  If manufactured to the Chinese standard, these will stop large droplets (3 micron) fairly well, but not viruses.  The US does not have a standard for these.  The US only had standards for surgical masks:

Surgical mask standards:  BFE and PFE.  An excellent summary of the difference between single-use masks, surgical masks, and respirators can be found at Smart Air Filters.  They explain it much better than I do.

Edit:  CORRECTION.  I have now located a proper description of surgical mask standards, from Primed, which I am going to crib here.

1. BFE (Bacterial Filtration Efficiency): BFE measures how well a surgical mask mask filters out an aerosol consisting of 3 micron droplets containing staph.  In order to be certified as a surgical mask, the cloth has to filter out 95% of those droplets.  Better grades of mask (mderate and high protection masks) must filter out at least 98% of those droplets.

2. PFE (Particulate Filtration Efficiency): PFE measures how well a mask filters out virus-sized particles.  They are supposed to be tested with particles of 0.1 micron size (about the size of coronavirus).  The higher the percentage, the better the mask filtration.  Apparently, some masks are tested with somewhat larger particles, and can show a misleadingly high PPE.

Note that the actual performance of a surgical mask, in use, will not be as good as these filtration rates suggest, because the mask does not seal up against the face.  (See Mask versus Respirator).  Air leakage around the edges of the mask compromises the overall filtration.  The standards above show the filtering ability of the cloth, not the overall mask assembly as a whole.

Edit: WRONG. Note that surgical masks are NOT tested for their ability to stop penetration by bacteria in the air.  They ARE tested against penetration by fluids, and penetration by bacteria and such in fluids.  They are designed for health care workers who need to avoid being infected by fluid-borne bacteria and viruses.  As far as I can tell, that’s why a proper surgical mask, tested and certified for health care use, has some ability to filter particles.   Most (some?) are made with three-ply construction, the middle ply of which is some form of melt-blown cloth.

And, helpfully, melt-blown cloth is also used in some (but by no means all) home furnace filters ( (see this manufacturer’s page).  Which gives me the segue to comparing the standards above to two that homeowners are familiar with:  MERV and HEPA.  And here, I assume you all know I am not talking about standard fiberglass, very-open-weave filters.  I’m talking about the ones that look like a sheet of fuzzy cloth.

MERV:  Minimum Efficiency Reporting Value.  From Wikipedia.

The scale is designed to represent the worst-case performance of a filter when dealing with particles in the range of 0.3 to 10 micrometers. The MERV value is from 1 to 16. Higher MERV values correspond to a greater percentage of particles captured on each pass, with a MERV 16 filter capturing more than 95% of particles over the full range.  (That little factoid will be important for tomorrow’s post.)

Do two MERV 8s make a 16?  No, absolutely not.  The MERV rating is like a pore size.  As you go up the scale, in groups of four, they start filtering smaller particles.  The 8s simply have larger pores, in effect, and let the smallest particles pass through.  That’s clear from this full explanation of MERV ASHRAE chart.  (But, if I’m reading that right, two MERV 14s, in sequence, come very close to achieving the same filtration as a MERV 16.  And two MERV 15s in sequence exceed that).

HEPA:  High-efficiency particulate arresting.  Again, from Wikipedia:

“Filters meeting the HEPA standard must satisfy certain levels of efficiency. Common standards require that a HEPA air filter must remove—from the air that passes through—at least ..  99.97% (ASME, U.S. DOE)[5][6] of particles whose diameter is equal to 0.3 μm; with the filtration efficiency increasing for particle diameters both less than and greater than 0.3 μm.[7] 

The little μm thing is microns (micrometers).

MPR:  Microparticle Performance Rating.  This is a propriety rating system developed by 3M.  It reflects the ability of a filter to capture the smallest airborne particles—from 0.3 to 1 µm in size (Wikipedia).  So you have to get the detailed 3M literature, if you want to look at Filtrete electrostatic filters:  https://multimedia.3m.com/mws/media/1740587O/filtrete-merv-vs-mpr.pdf

Filtrete (r) filters differ from MERV-rated filters in that all varieties of Filtrete capture some small particles.  If you look at E1s (the smallest particles, down to 0.3 micron), it appears that you need two layers of MPR 2800 Filtrete to achieve 95% or more of filtration of E1 particles.  Although, for particles one micron and up, one layer of MPR 2800 or one layer of MPR 2500 would achieve 95% capture of those particles in a single pass.

I am uncertain as to how that Filtrete electrostatic material behaves under adverse conditions, such as when damp.

Filtration properties of common household materials. 

This is where the rubber hits the road.  Start with this article, where they actually tested cloth and made masks.

Here’s one key table, below

This is a pretty good setup, because they literally aerosolized the bacterium and virus, then tested what happened when they pushed that aerosol through a cloth panel at about the rate you would if you were breathing.  These particles are certainly on a par with the size of the coronavirus itself, and presumably the aerosol droplets are about the best proxy you are going to find for … well, aerosol droplets.

First, note the similarity of the first two columns, despite the differing size of the bacterium and the virus.  That’s because, by and large,  the masks are catching the droplets, not the individual bacteria and viruses themselves. The standard here is the surgical mask, circled in red.  I note that a vacuum cleaner bag (not stated as to type, likely not HEPA, because I’m pretty sure they are talking about cloth bags) was just about as good as a surgical mask — I put a red line there.  And a tea towel, doubled over, was just about as good.  But in the right-hand column, that’s the back-pressure you would face, in breathing through those materials.  The vacuum-cleaner bag and the doubled-over tea towel were 2 to 2.5 times harder to breathe through than the surgical mask material.

Source: Testing the efficacy of homemade masks: would they protect in an influenza pandemic? Davies A1, Thompson KA, Giri K, Kafatos G, Walker J, Bennett A.  Disaster Med Public Health Prep. 2013 Aug;7(4):413-8. doi: 10.1017/dmp.2013.43.

This is important, because the harder the material is to breathe through, the more air will leak around the mask, rather than through it, and reduce the overall filtration efficiency.

So, to be clear, yeah, you can find stuff around the home that will give as much filtration efficiency as a good surgical mask (but not an N95 mask).  But it’s going to be somewhat hard to breathe through.

And, if you care, read the section of that paper on fitting the mask.  All of the home-made masks were much leakier than a good-quality surgical mask.  That’s important, and that’s what you need to focus on if you make a mask.

Finally, how much better is it to wear a home-made mask, made out of a cotton t-shirt, than to have no mask at all, in terms of containing the spread of disease (from people coughing, in this case).  Well, they tested that empirically:  Literally had people cough, through a mask, into a sterile box, and counted the crap that came out.

 

Source:  Same as prior table.

Do home-made masks help prevent the spread of contagion?  Heck yes.  Look at the bottom line:  No mask, 200, homemade mask, 43, proper surgical mask, 30.  That’s the count of bacterial “colony-forming units” that they observed.  Do the math, and a home-made mask gets you (200-43/200-30) = 92% of the reduction that you would get from a standard high-quality surgical mask.

Now in case you’re surprised by that, my reading of it is that anything that stops droplets from flying is good.  You aren’t literally trying to filter out tiny little viruses.  You are trying to filter droplets, most of which you can catch with cloth, some of which fly right through.

Filtering ability of paper towels.  I didn’t find a scholarly article (and got tired of looking), but these people seem to have their act together.  It’s one of those great articles that just gets to the point.  And the short answer is that common household paper towels, do, in fact, have some measurable ability to filter out particles in the size range we are talking about.

For very tiny (0.3 micron) particles, “A single layer of kitchen paper captured just 23% particles. Adding an extra layer only increased particle capture to 33%.”

But for aerosol-sized particles (smaller than “droplets”):  “For larger 2.5 micron particles, paper towel performed better. The single layer of kitchen paper captured 52% of these larger particles”.

(From that, I would infer that two layers would get 75% or so.)

Those same folks provide a nice graphic re-write of the article on home-made masks, at this location.

Near as I can tell, nobody has done the one I want to see, which is a coffee filter.  I use(d) those as a pre-filter when purifying raw water when camping, and I think that’s a pretty common use.   I did test that you could breathe through one (possible, but a lot of resistance).  I will keep looking for that one.

Bottom line:  Wear ’em if you’ve got ’em.  If not, buy one and modify it.  If not, make one from scratch.  Any mask is better than no mask.  Even paper towels have some filtering efficiency. 

Next post is about buying and modifying masks.

Final post will be about making masks.  But you can just go on Amazon and get a free Kindle download on that.

Post #527: W&OD bridge?

Two of the W&OD road crossings in the Town of Vienna will be updated, based on suggestions in the Town’s Maple Avenue Multimodal etc. study.  The W&OD road crossings at Park Street and Church Street will get raised crosswalks, turning them more-or-less into speed humps.  And they’ll get new signs.

It’s tough to say why, of all the things in that study, the Town decided that those two W&OD road crossings were a priority.  For sure, there was no formal cost-benefit or risk analysis done.  I think they just sort of liked the idea, and it was cheap to do.  So they’re going to do that, and that’ll be the tangible outcome of that study, along with filling in a right-turn lane where Mill and Church intersect.

This seems to have stirred up some interest in a W&OD bridge for the Mape Avenue/W&OD crossing in the Town of Vienna.  To be clear, we’re not getting a bridge there, and nobody is talking about paying for a bridge.  And in this post, I’m briefly going to explain why that is — why this was ignored in the Town’s Multimodal study, and will it will likely remain a low-priority issue.  My conclusion is that the stoplight we have now for the W&OD Maple Avenue crossing is probably good enough, given the size and cost of a bridge.

 

But other crossings have bridges …

Sure, but those crossings tended to be ones with significant problems and traffic, often where a new traffic light would not work, or where there are problems, despite a light, due to heavy traffic.

The closest large dedicated bridge on the W&OD is the Citizens’ Bridge in the People’s Republic of Falls Church.  This is where the W&OD trail crosses Route 7/Broad Street.  This bridge dates to 1992 or so.  Falls Church citizens agitated for a bridge because bicyclists and pedestrians were crossing Broad Street there, rather than walk/bike to the stoplight-controlled intersection at West Street.

That bridge is an object lesson in the nature of bicycle and pedestrian traffic.  At the time, the bridge was lauded as an example of effective small-town government.  But one could just as easily say it’s there because various bicyclist and pedestrian scofflaws routinely jaywalked rather than walk an extra 200 feet to cross with the light (while getting their exercise along the W&OD trail.)

More recently, the influx of new tax and toll monies means that all kinds of marginal and low-value projects are now being funded, as long as they plausibly help people get around without a car.  This includes a spate of new bridges for the W&OD.  These tend to be for intersections where the road crossings were an annoyance to bicyclists and/or motor vehicles, though not particularly dangerous (at least in my opinion).

There’s a bridge going up for the Route 29 crossing just east of Falls Church, and a bridge is planned for where the W&OD crosses Wiehle Avenue in Reston.  Neither of these is a particularly difficult crossing now, although Weihle is awkward because it’s so close to a stoplight with no place to stop in the median.  Both of these crossings, though, apparently have fairly high automobile accident rates, as cars stopping for bicyclists get rear-ended with some frequency.

Above:  Route 29 W&OD crossing just east of Falls Church, and Weihle Road crossing in Reston.

In essence, right now, these are just crosswalks used by a lot of bikes.  Not unlike the W&OD crossings in Vienna.  But soon those simple crosswalks will be replaced by some fairly large and obtrusive bridge structures.  Here’s a “before and after” view of Weihle Avenue where it crosses the W&OD trail.

Above:  Wiehle Road crossing now, and Wiehle Road showing artist’s conception of bridge.  (Orient by trees in background).  Source for Weihle bridge:  FCDOT via restonnow.com

So why not Maple Avenue in Vienna?

It boils down to need, cost, and size.  And all of these argue against a similar structure at the W&OD crossing on Maple Avenue.
First, the existing light-controlled crossing works well.  We have the occasional bicycle scofflaw crossing against the light.  But in my experience, those are few and far between.   And that’s because that current path is in fact the shortest distance.  So we do not have the problem that Falls Church had, with a constant stream of jaywalkers who were unwilling to walk to the nearest light-controlled intersection.
Second, a bridge there would necessarily be fairly large.  And it’s not that you need a massive structure to move the bicycles.  It’s that VDOT requires a minimum 17.5′ clearance (I just looked that up), and bike paths are never supposed to have more than a 5% slope if that can be avoided.  When you combine those two (17.5′ tall, 5′ slope) you realize the bridge would have to span Maple Avenue and 350′ on either side of Maple.
The upshot is that the entire bridge structure (including earthworks at either end) would have to span about 750′ (350′ + 350′ plus the width of Maple).  No coincidence, this is roughly the length of the Citizens’ Bridge in Falls Church.  So, if you look at that (above), that’s more-or-less the minimum size of structure that you can get away with.  Not due to the load of the bicycles, but due to the combination of clearance and slope limits on the structure.
So the very smallest it could be, built to those standards, would be a span from almost Church Street at one end, to almost the end of the Whole Foods market at the other.   This would cut Maple Street off from the trail and make trail access difficult.  (In fact, some of the opposition to the Falls Church Citizens’ Bridge came from local merchants who saw the bridge as discouraging bicyclists from stopping (and spending money) in Falls Church.  See the newspaper article cited above.)
It will also cost somewhere in the neighborhood of $6M to $12M.  Or so.
 
A internet search shows the cost of steel pedestrian bridges runs about $2000/linear foot for a prefab steel footbridge such as the Falls Church one. Of the 700′ length, the Falls Church Citizen’s Bridge is roughly 400′ of steel bridge, and the rest earthworks.  At that price, the steel bridge alone would cost about $8M.   So call it $10M or so, based on that.  
A second data point comes from the bridge slated for Weihle Avenue in Reston, which has a preliminary cost estimate of $11.4M, per the newspaper article cited above. 
 
A third data point is a reported cost of about $6M for what looks like a roughly-similarly-sized intersection (W&OD crossing four lanes of traffic).
Caveat:  The reported cost of the Falls Church Citizens’ Bridge, just under $1M, is vastly less than $10M after accounting for inflation.  Adjusting that circa-1992 cost for the Consumer Price Index change to 2020 yields about $2M in today’s money.  On the other hand, that initial cost estimate may have been in error, as the $11.4M Weihle Avenue bridge was originally supposed to cost under $3M.
So, maybe not exactly $10M, but somewhere in that ballpark seems likely.
In summary:  The current Maple Avenue W&OD crossing appears safe, appears to have relatively few bicyclist scofflaws, and in general provides easy on/off access to the W&OD in the heart of Vienna.  Any bridge there would necessarily be large and fairly expensive.  It’s easy enough to see why other intersections have gotten bridges before anyone would think of funding a bridge for the Maple Avenue W&OD crossing.

Post #521: The cost of sidewalks

Source:  Google maps.

The point of this post is pretty simple:  The cost of installing new concrete sidewalks various enormously.   And the cost of the sidewalk itself — i.e., the 5′-wide ribbon of concrete — is the least of it.  The bulk of the cost is in everything else that has to be done — curb, gutter, curb cuts, ramps, and, most importantly, drainage including storm sewers.

To make this point, I identified four sidewalk projects in the Town of Vienna, and estimated cost per linear foot.  (Detail given below.  This is a “sample of convenience”, being the first four projects I ran across.)  The costs were $100, $150, $445, and $666 per linear foot of sidewalk.  Presumably, if I’d looked at a larger sample of projects, I would have seen even more variation.

In the Town of Vienna, a) there’s really no meaningful “typical” cost for putting in sidewalks and b) in any given situation, the cost might be a lot more than you’d think.

The high costs of sidewalks — and the fact that literally “the sidewalk” is typically the smallest part of the cost — has some important implications for a couple of items that I’ve mentioned recently.

Robinson bequest for sidewalks.  At the last Transportation Safety Commission (TSC) meeting, I found out that the Robinson estate bequest for sidewalks in the Town of Vienna was being interpreted as literally that:  payment for the concrete sidewalk, period (Post #518).  Depending on the project, then, the Town would have to pay for everything else to make that sidewalk possible.  That’s certainly going to tilt the use of those funds toward simple projects where (e.g.) there is already curb and gutter in place, with no need for extensive modifications for site drainage.

Sidewalks versus road closure for the neighborhoods behind Sunrise/444 Maple West.  At the last Town Council meeting, citizens offered some things the Town could do to address pedestrian safety and traffic in the neighborhoods adjacent to the proposed Sunrise facility (Post #517).  Among those was the idea of putting in sidewalks on (among other) Glen Avenue.  But Councilman Potter suggested that simply closing Wade Hampton at Glen would be a less costly solution.  And based on these per-foot costs, that seems like a plausible statement.  Based on those four costs per foot, 1400′ of sidewalk for Glen Avenue (pictured above) might cost anywhere from $140,000 to more than $900,000. 

Continue reading Post #521: The cost of sidewalks

Post #519: The tear-down boom and increased residential share of Town property assessments

This is just a quick back-of-the-envelope spurred by a presentation made by the Town’s Director of Finance at the 1/27/2020 Town Council meeting.

One statistic that caught my eye is that the residential share of total property assessments in town rose over the last decade, from 77.5% in 2011 to 81.0% in 2019 (Page 9 of this document (.pdf)).  The Director of Finance suggested that this was one possible justification for hiring the new business development officer for the Town of Vienna.  That is, to help bolster Vienna business and hence assessments.  Conversely, Councilman Majdi suggested that the tear-down boom might account for it, with small houses being torn down to make way for much larger ones.

So, that’s the question here:  Does the increase in residential share of total property assessments mean that commercial real estate in Vienna showed poor price appreciation, compared to residential?  Or is that plausibly just a consequence of the tear-down boom, with small, lower-cost houses in Vienna being systematically replaced by larger, higher-cost houses?

Here, in the crudest way possible, I want to test that.  Can the tear-down boom plausibly account for this change?  In keeping with the idea of a round-numbers calculation, I’m going to do a crude cut at this.  Basically, is the impact of the tear-down boom anywhere near large enough.

So:  My recollection is that, of late, the Town has averaged about 100 tear-downs per year, based on building permit data.  Further, based on a couple of observations, property value for a tear down typically increases by about a million dollars (in 2019 terms), from (say) $0.7M for a small house, to $1.7M for the typical mansion that replaces it.

So, 9 years x 100 houses per year x $1M/house = $900M in additional residential property values, in 2019 dollars, from the cumulative effect of the tear-down boom from 2011 to 2019.   Roughly speaking then, if I net out the crude impact of the tear-downs, I get this table:

Crude impact of tear-down boom on Vienna assessed real estate values
Residential Total Residential %
Actual 2019 4,251,761,320 5,204,854,490 81.7%
Less tear-down impact 900,000,000 900,000,000
2019 less tear-down 3,351,761,320 4,304,854,490 77.9%

And the answer is that the (crude estimate of the) impact of the tear down boom is more-or-less the right size to explain the shift in assessment share in the Town of Vienna.  The difference between the two red numbers, in the table above, is roughly as large as the difference between the two red numbers in the opening paragraph.

In other words, this shift in assessed values in the Town of Vienna doesn’t show any particular problem with our commercial real estate.  Plausibly, it just shows the impact of the replacement of small, lower-cost houses with much larger ones.

This is consistent, I think, with repeated mentions of high rental rates for commercial property along Maple (e.g., in the new Town economic development officer’s “listening tour”).  The complaint is that high rental rates are driving businesses out of Vienna.  But if so, that’s just an indication that business is good along Maple.  Nobody likes paying rent, but if property owners along Maple think they can get (e.g.) $60/square foot/year, that means they expect that business opportunities are such that some business can afford to locate on Maple and pay that kind of rent.

Post #513: Light trespass and protecting housing adjacent to Maple

The Chick-fil-a-car-wash is in the process of getting some exterior modifications to reduce light trespass, that is, excessive and annoying spillover of light onto adjacent properties.  In this case, the spillover is from the interior lighting of that building onto the nearby townhouses.  Councilman Potter championed this change on behalf of the adjacent neighborhood.  Approval for those modifications was supposed to occur at the last meeting of the Board of Architectural Review (BAR), but was postponed.

So, good for them, for being willing to make the changes to reduce their light trespass.  But you have to ask a) why does a brand new building need this retrofit, and b) is this a one-off problem, or a generic problem that needs to be addressed for future buildings as well?

The answers, as far as I can tell are that a) the Town only checks for light spillover on paper, not in the field, and those paper estimates of light spillover have many shortcomings, and b) yeah, there are already indications that this is an underlying problem that should be addressed more broadly and more proactively.

What I’m saying is, don’t think of this as some sort of one-off mistake.  It’s a single example of a generic shortcoming of the zoning process.  It should be addressed as such.  In much the same way that I argued for changing the code to require closing in garages that face residential areas (to control noise pollution), the Town needs to step up its game and provide real checks on light trespass from new commercial development. Continue reading Post #513: Light trespass and protecting housing adjacent to Maple

Post #511: Three followups to the last Town Council work session

Source of this image is linked here.

This is about three unrelated points from the Monday Town Council work session that, in hindsight, struck me as possibly worth writing up:  The Town traffic simulation, the treatment of the Town strategic “plan”, and the end game 18 to 24 months from now.

Town traffic simulation.

Part of the Town’s “Multimodal” traffic study estimated the impact on traffic congestion from Maple Avenue development.  I’ve spent a lot of time trying to figure out what the consultants did to arrive at their numbers.  As of last night’s meeting, I have officially given up on that, because I can’t make head or tail out of it.

But I did take away one thing from trying to puzzle that out:  There’s a lot of uncertainty (wiggle room) in that calculation.  That’s worth noting, I think.  See if you can follow this.

  1. Back in August, the contractor presented results showing 758 additional net new evening rush-hour trips from Maple Avenue redevelopment.  They did not talk about it during that presentation, or during their next presentation.  But it was on a slide that they skipped over (Post #358).
  2. One issue I had with that is their “baseline” traffic, i.e., the number of trips that they assumed occurs right now.  Their graphic clearly showed that they assumed that (e.g.) currently-empty buildings were generating traffic on Maple.
  3. The single worst example of that was the assumption that the Suntrust Bank (east) currently gets 381 trips in the afternoon rush hour.  As previously noted, that’s a ludicrous number — it amounts to one car going into or out of that bank parking lot every 10 seconds.  Councilman Majdi called them out on that, but both the contractor and Town Manager strongly defended that as “science”.  I was so ticked by that misuse of the term “science” that I sat in the bank parking lot and counted cars to demonstrate that the actual traffic to that building was about one-tenth of that (Post #465).
  4. When I want to look at the final report, I couldn’t find those 381 trips.  As it turns out, at yesterday’s work session, it was revealed that the contractor removed those 381 existing trips from the baseline.  Simply zeroed them out.  That’s why they are no longer in the report. And so, presumably, we have no further cause for complaint.
  5. OK, fine, I can do arithmetic.  If they remove 381 from the baseline, that should then add 381 to the net new trips.  (Why?  Because you net out the existing traffic, when calculating the net new traffic.  If you reduce existing traffic by 381, then you should have increased the net new traffic from development by 381.
  6. And yet … in the final report, the net new trips from Maple Avenue actually decreased from 758 to 500.

So, without pondering how they justified that, just do the math.  Focus on the simple arithmetic of how they had to have gotten from the prior estimate to the current estimate.  Solve for X:  758 + 381 + X = 500.  Turns out, X = -639.  That is, they managed to extract a further 639 net new trips out of their analysis, to get from the original estimate that (presumably) netted out the Suntrust 381 in the baseline, to the final estimate that did not.  Just as a matter of arithmetic.

This X factor of -639 trips is what economists call a structural uncertainty in the estimate (as opposed to a statistical uncertainty).  It’s the uncertainty that arises from doing the numbers one plausible way versus another (as opposed to a more traditional statistical uncertainty, which arises from purely random factors, so to speak).

So this lower bound for the true stuctural uncertainty of the estimate — how much it changes based on choices made by the analyst — is larger than the estimate itself.

A lot of other things about the methods and results looked counterintuitive to me.  For example, the net new traffic during the AM rush hour, to the extent that it left Vienna, flowed mostly westward (i.e., against the direction of morning rush hour traffic).  About 2.5x as many additional cars exited Vienna at Nutley as at Follin.  But put those issues aside.  The simple arithmetic of getting from the draft to the final — the X above — is what convinced me that I would never have any real understanding of how they arrived at their numbers.

So this is truly a black box, and a black box it shall remain.  There are open-source software packages that allows individuals to model transportation networks (e.g., here, here, or here.)  All of them require considerable amounts of data as input (e.g., traffic light timings, traffic counts).  I’m not going to put in the effort to try to gin up my own estimate.  But my conclusion is that this is the only way to avoid having the results be a total black box.

Addendum:  Traffic counts and the K-Q curve.

Addendum:  I also have no clue what these traffic models do when actual traffic passes the peak of the “K-Q curve”.  (Briefly, as you try to stuff more and more vehicles through a given roadway (increase the density of cars per square foot, traditionally represented by “K”), each individual car may move more slowly, but in aggregate, the total flow of cars (represented by the letter “Q”) increases.  That is, at first, each car may move slower, but you get more total cars moving through the road segment.  But as you continue to add cars, you reach a point where the reverse is true:  You get so crowded that adding more cars actually reduces total traffic flow.  Not only does each car move more slowly, but you actually get fewer total cars to pass through the road segment in a given amount of time.  That point — where jamming more cars onto the road actually begins to reduce not just speed, but total traffic flow — that’s the peak of the K-Q curve, as in this diagram (k = density of cars, q = total flow of cars through the roadway, v = average car speed).

Source:  Wikipedia.

As I understand it, this is the reason you will see (e.g.) metered on-ramps (ramps with traffic lights) at the on-ramps to the inside-the-beltway portion of I-66.  They are trying to avoid passing the peak of the K-Q curve.   Once you pass that peak, you are helping nobody by allowing more cars onto the roadway.  Not only does every individual car move slower, but you actually get fewer total cars to pass down the highway in a given amount of time.  All you do is increase the size of the backup.

It sure seems to me that we hit the peak of the K-Q curve during morning rush hour.  At least sometimes.  At the point where traffic from the Courthouse and Maple light backs up all the way to Nutley, it’s tough for me to imagine what we haven’t hit and passed the maximum possible through-put of the Maple-Courthouse intersection.  Here we are, just before 9 AM, looking east and west on Maple, at the Nutley Street intersection.

But here’s the technical question.  Look at the diagram above and think of the curved line as a hill.  In terms of traffic counts, you get the same traffic count if you are halfway up the upslope of the hill (before the peak of the K-Q curve, where traffic is light and moving well) as you do halfway down the downslope side of the hill (past the peak, where traffic is packed and moving slowly).

I think this explains one oddity of the report, in that the consultants seem to think that we have one long rush hour period from about 8 AM to about noon.  Because they are looking at the traffic counts, and the flow of cars is about the same throughout that period.  Like so:  The flow of traffic (cars/hour) is the same at 9 AM as it is at 11 AM.

Source:  Vienna multimodal transit report, 12/20/2019 draft, page 3-13.

But as anyone who drives that road can tell you, there’s a stark difference in the level of traffic queues or waiting times between 9 AM and 11 AM.  Just before 9, traffic routinely looks like the pictures above.  Whereas around 11 AM, traffic flows far more freely.  But you see no difference on the graph above, because the traffic counts, by themselves, are blind to the fact that Maple hits capacity during the rush hour.  The count you get when you are on the downslope side of the K-Q curve (just before 9 AM, with huge backups as pictured above) is the same as the count you get when you’re still on the upslope of the curve (around 11 AM say, when traffic moves pretty well).

So that’s just an oddity that I noticed.  Traffic counts (cars/hour) do not, by themselves, accurately measure traffic, because of the ambiguity caused by hitting the peak of the K-Q curve.  Very light traffic and very heavy traffic can generate identical traffic counts.  And the graph just above doesn’t show that we have one long rush hour.  It just shows that the total traffic counts don’t change much between the absolute peak of the AM crunch (which I place at about 8:45 AM) and the must less crowded mid-morning period.  I think that, as much as anything, demonstrates that we hit some measure of capacity on Maple during AM rush hour.  Once you hit capacity on Maple — as I infer that we due during the AM rush — additional traffic does not result in additional traffic counts.

I’ll mention one other truly weird possibility.  At this most recent meeting, Coucilman Noble made much out of the new traffic light system that Vienna is getting.  (I have the vague notion that VDOT, not the TOV, is responsible for that, but that doesn’t matter).  If that traffic light system actually increases throughput during the periods when Maple is at capacity (something that I doubt will happen, per discussion of capacity above, but is possible), then, by traffic counts alone, it will make it look as if traffic has gotten worse during rush hour.  That’s just another example of the way in which traffic counts, alone, can provide a misleading indicator of traffic when a road is at capacity.  If there’s a fundamental change in the roadway (in this case, new light timing), traffic (counts) going up can mean that traffic (wait times) is going down.

And as a final, final note on that, if the Town of Vienna wants Vienna citizens to be aware of some profound benefit they are going to get from new traffic signals, I suggest that they actually provide at least some sort of description of what they intend to do.  Near as I can tell, the entirety of what Vienna has to say about this project is a total of 23 words on this page on the Town of Vienna website.  Normally, as you may realize, I will do my homework to understand what the Town is about.  But from the description, I can’t even find the words to Google up what this is.

 

Town Strategic “Plan”

In theory (and by law), anything the Town of Vienna government does needs to comply with the Town’s strategic plan.  But if you look back at when the Town developed MAC zoning, they developed MAC zoning (2014), then rewrote the strategic plan (“mixed use development) to match it (2015-2016).

This more-than-begs the question of what you mean by “plan”, if you rewrite the plan to match what you subsequently decided to do.  I have a vague idea that it isn’t even remotely legal to do that.

That said, based on the last work session, that’s the plan going forward.  When Councilman Majdi brought up the idea of addressing the comprehensive plan first, that was (of course) immediately shot down.  The agreed-upon sequence is now to rewrite the zoning (with apparently no restrictions whatsoever), and then once again rewrite the comprehensive plan to match whatever comes out of the zoning rewrite, if necessary.

Just in passing, and to underscore how loosey-goosey this is, Town staff have now set it up so that this Town Council is actually providing less guidance to this process than occurred during the original development of MAC zoning.  At least, under MAC, Town Council somehow arrived at a firm limit on building height.  Here … near as I can tell, anything goes.  Town Council has not publicly agreed on even one single thing that they want to see in a revised MAC zoning.  It’s all up to the Department of Planning and Zoning.  That’s no surprise, given that Planning and Zoning appears to be controlling this process.

Looking 18 months down the road.

Fundamentally, the limit on the density of development on Maple Avenue appears to be a political limit.  It’s really about what the median Vienna voter wants.  There’s no technical barrier to filling Maple Avenue with Chick-fil-A-car-washes.  It’s just that the people who live here do not, on average, seem very fond of that idea, and they will vote for people who say they won’t do that.

This is all the more true if you purposefully ignore any other possible limits to growth.  E.g., if you will not discuss development in the context of the capacity of Maple to move traffic, or in the context of impacts on nearby residential neighborhoods.  Barring all that — if you acknowledge no other limits — then the only limit on the density of Maple Avenue development is a political limit.

This is a point that Councilman Majdi brought up at that work session.  And either his fellow Council members didn’t get it, or they just shot it down as sort of knee-jerk reaction.

So I need to point out the following:  Town staff have structured this process so that our elected officials have no say in shaping the new MAC.  They will have no formal input in what happens to MAC zoning until the very end of the process.  The process will be controlled by the Department of Planning and Zoning, with input from the Planning Commission (still largely staffed by holdovers from prior Town Council.)  Only at the very end of the process will Town Council be presented with the finished products.

Councilmember Patel tried to reverse that — to get Town Council to have first say over the shape of the revised MAC zoning — and got quashed by the pro-MAC members of Town Council.

So I’m just pointing out the disconnect here.  The only functional limit on MAC density is a political limit.  And our political body is (formally, at least) completely shut out of the process of shaping the new MAC, until the very end.

The only logical conclusion is that this is likely to end (or, at least, risks ending) in some sort of train wreck.  The people actually structuring the new MAC are not subject to any political constraint — they are not elected.  And the people who are elected are not part of the MAC-rewrite process.  That’s exactly what the response to Councilmember Patel established.  But in the end, the constraint on what can and can’t be done is a political one.   So this is a fundamental mis-alignment of incentives, and poor overlap between scope of authority and scope of responsibility.  Town Council is going to be responsible for what comes out of this process, but they have been stripped of all authority to shape it.  

What guarantees that Town Council will be handed a new MAC that is politically acceptable?  Nothing.  The process is literally and purposefully structured that way.  Any notion that Town Council would offer overall guidance (by having first crack at proposals) was firmly snuffed out at this past Town Council work session.

And that’s the scenario that I reckon as a train wreck.  Suppose the very-pro-development Department of Planning and Zoning, working in a political vacuum, comes up with a zoning proposal that appears unacceptable to the median Vienna voter.  Then what happens?

I believe that Town staff are actually counting on that possibility of train wreck.  That is, they are counting on being able to cram this down Town Council’s throats, at the end of the process, one way or the other.  They think that those who oppose larger buildings and higher-density development will blink, in order to avoid that train wreck.  (E.g., to avoid vetoing a proposal that too two years and a quarter-million-dollar contract to develop, and that includes a bunch of purely technical and non-controverial fixes to Town Code in addition to a rewritten MAC.)  By refusing to separate out the non-controversial “clean up” portion of this work, from the more controversial changes to Town zoning, they can given Town Council a one-vote take-it-or-leave it choice (as I have already noted, per Post #483 and others).

Or, possibly, they are hoping that this next election will lead to a change in the fortunes of the pro-MAC portion of Town Council.  So that by the time this comes to a vote, they’ll have the votes for a higher-density MAC zoning.  That’s certainly possible.  From what I can tell, the anti-MAC forces seem totally disorganized at this point.  I guess we’ll have to wait and see.

Post #505: Revisiting #2: Let’s move the Noah’s Ark meeting into the 21st century.

Read Post #480 for the definition, and Post #495 for how this applies to Town’s decision to establish the rules for rewriting all the zoning in Vienna in private, out of the public view.

In a nutshell:

  • Under the Virginia Freedom of Information Act (FOIA), any time three* or more members of a public body gather to discuss public business, that’s a public meeting.
  • All public meetings have to be open to the public, unless there’s some well-defined reason for having a closed meeting.  The statute identifies a specific list of such reasons (e.g., personnel actions).
  • A meeting of two members of a public body is not a public meeting.  It has to be three or more.

* Or, if a quorum is fewer than three.  So if there’s a two-person subcommittee, if those two people meet to discuss public business, that’s a public meeting.

OK, now think like a bureaucrat.  How do you dodge the clear intent of the Virginia FOIA, and manage to hold a meeting of (e.g.) seven members of the Town Council, but bar the public?

Simple:  You break your meeting up into little pieces, where each piece only has two Town Council members present.  Let me term each such piece of the overall meeting a “meetinglet”.

A single meetinglet, by itself, is more-or-less useless.  But now, instead of one meeting with all seven present, you hold a coordinated series of meetinglets, one after the other, with Town Staff providing information on what has been said in all prior discussions.  For legal purposes, instead of that being treated as one meeting of seven people that has been broken up into meetinglets, the law treats each meetinglet separately.

Hence, “Noah’s Ark” meeting, because you bring in the Town Council two-by-two.  You break the seven-person meeting into a series of two-person meetinglets, and presto, it’s legal.

Continue reading Post #505: Revisiting #2: Let’s move the Noah’s Ark meeting into the 21st century.

Post #488: A followup and correction on the 2020 bond issue

For the record, I need to correct what I said about the 2020 bond issue (Post #485).  It’s the part where I summarized it as: “Can they really pay that back?  I think the answer is a qualified yes.”

I believe that’s not true if they borrow the full $35M that they have been authorized to borrow.  I don’t think they can do that without violating their stated minimum reserve requirements for their capital fund, based on their current economic model.  And I didn’t realize that until I saw all the details presented at last night’s Town Council meeting.

I realize it’s too late to do anything, as the Town Council approved the bond issue.  But I think it’s worth stating this for the record.  Just on the off chance that anybody in Town government cares about it.  Presumably, Town staff will redo the reserves calculation just prior to the time of bond issuance using updated information.

Continue reading Post #488: A followup and correction on the 2020 bond issue

Post #473: No standards for pedestrian sight lines

This post is a courtesy for the Vienna Transportation Safety Commission (TSC).

The first point is to provide a convenient reference to Post #424, which is my summary of the Chick-fil-A drive-through exit hazard.  In a nutshell, I think that the obstructed view of the sidewalk there constitutes a clear hazard to pedestrians and bicyclists, on what is now a walk-to-school route thanks to the Madison HAWK light.

At tonight’s (11/25/2019) TSC meeting, I’m going to ask the Town to do something about that.

My second point is that there does not seem to be any technical guidance on this issue whatsoever, from either the Virginia Department of Transportation or from Federal sources.  The issue being, specifically, when a driveway meets a sidewalk next to a public road, what constitutes adequate sight lines between drivers in the driveway, and pedestrians on the sidewalk.   (So, not an issue of driver-to-driver sight lines, but driver-to-sidewalk-pedestrian sight lines.)

Best I’ve seen, so far, from VDOT or federal sources, is a vague statement that one should have adequate sight lines.  And that’s in the context of roadway intersections, not driveways entering a roadway.

After considerable searching, I found a handful of municipalities that addressed this exact issue.  Near as I can tell, all of them ask for the area to be kept clear of visual obstructions 10 feet or more back from the sidewalk, when a driveway enters a roadway.  This should be contrasted with the 1-foot distances between the sidewalk and the obstruction (a 5′ tall transformer box) at the Chick-fil-A drive-through exit. 

So, if you were looking for solid evidence that the situation at the Chick-fil-A drive-through exit is hazardous, here are four cities that would have banned it.  These are all standards for vehicle-pedestrian sight lines.

Lincoln, NE (.pdf) says you can have no obstructions with 10 feet of the sidewalk where a driveway enters a street.  Like so:

City of Kirkland, WA requires a 22′ setback, as measured along the sidewalk, but they assume that cars will be moving 10 MPH down a driveway.  Not sure this is relevant.

Bellevue, WA says 14′ from the back edge of the sidewalk must be kept clear, but that’s measured in the middle of the travel lane.

City of Albuquerque requires 11′ be kept clear around residential driveways.

I think this is enough to show that where this issue of pedestrian visibility at driveways is explicitly addressed, the required setbacks from the sidewalk that must be clear of visual obstruction vastly exceed what we have at the Chick-fil-A drive through exit.

Post #462: On mail-based surveys and other methods to gather public opinion

The proximate issue is Councilmember Patel’s proposal to have a short survey routinely included in the Vienna Voice, the Town’s monthly newsletter.  I judge that Town staff’s response to that proposal was not an even-handed discussion of the issues (Post #461).

In fact, I was so flabbergasted by Town staff’s response that I’m having a hard time figuring out what to write about it.  And not just because some of it was wrong on the facts.  (Or some of the straw-man assertions.  I thought “Is Council setting an expectation that all decisions will be made by referendum” was particularly over-the-line.)

What really astonished me is that virtually everything they said, to knock the idea of a newsletter-based survey, goes double and then some for every alternative that they suggested.

From the standpoint of statistics, more-or-less all the things that they thought were wrong about a newsletter-based survey are even more wrong about the alternatives they proposed.  And upon reflection, I think they genuinely don’t understand that.  There’s no reason they should.  They weren’t hired to be survey experts.

And I’m guessing they are trying so hard to quash this idea because they think it’s vastly inferior to various alternatives.  But it’s not.  And that’s what I’m going to concentrate on here.

As a means for:

  • determining what the average Vienna voter thinks,
  • in a way that is transparent, and
  • in a way that can be audited, where
  • the results are not the product of staff’s subjective interpretation of data,
  • using methods that we can afford …

It’s hard to beat a mail-based survey.  And the two large advantages of using the Vienna Voice for that are that we’ve already paid for the postage, and (probably) people will at least glance through it before they throw it out.

In case anyone cares, I have considerable bona fides in this area, having conducted surveys as a Federal employee and in other contexts.  Including, oddly enough, actually having used a newsletter to perform what was, and may still be, the largest-ever survey of Medicare beneficiaries’ difficulties in finding a primary care physician.

Continue reading Post #462: On mail-based surveys and other methods to gather public opinion