August 2020 - Edition 16, Urban Mass Transit


The summer is coming to an end, but you wouldn’t know if for the heat. We’re careening towards the fall and storm season (in my neck of the woods). To compound the stress, the school year has started. For those of you that don’t have school age children – I am very jealous. We’re only two weeks in and I don’t know how home-schoolers do it. But I’ve become more convinced that the distance during the day is crucial for the sanity of the parents and the children.

SES has hit a crucial point in its existence. At this point, the cost of maintaining the business is prohibitive if a contract doesn’t come through the door. But that may all change soon. There is the potential for a contract in the near future that will alleviate this issue and allow SES to keep its doors open. I’m trying to stay calm, but concurrently cheering for the best.

Demetri's Corner

After submittal towards the Desalination Prize, I’ve come to realize that if nothing else, I can indulge in my passion for trying to solve problems in weird ways – and if I’m lucky – get some traction.

Finalizing the white paper that describes the simulation used for the Skid-based Automated Flash Evaporator System (SAFES), located at, showed me the real potential of the system in terms of efficiency. I’ll look for opportunities to market the approach and see if the concept can be brought to reality.

Similarly, I’m working on a new concept of urban mass-transit based on moving sidewalks. I summarized it briefly in a design study (“Moving Walkway for Mass Transit” at, but thought I should flesh the thought out a little more. In the process I “solved” a lot of the problems that plagued my original vision and came to realize that as far as I can tell, the manner of solving the problem had never been proposed in the past. I’ve been persuaded to enter the patenting process for the idea and hardware. I’ll keep you posted on how it goes. The topic for this newsletter is directly related to the concept I’m patenting, but as the patent process is ongoing, I will minimize discussion on the specific solution, but instead focus on the problems with the current state of urban mass transit

Today's Subject - Urban Mass Transit

In today’s newsletter we’re going to talk about urban mass transit – the way people get around city centers and how people living in urban environments get to work, school, the grocery store, etc. We’ll start by working on a definition and then talk about the attributes that make a mass transit system “good”. After establishing what it means and defining redeeming characteristics, we’ll look at current approaches as well as future approaches and how they stack up. We’ll finish with some thoughts on the future of mass transit and a plug for my personal concept.


Most people would have similar opinions on what Urban Mass Transit means, but when pushed coming up with a consistent definition is difficult. For this newsletter we will define it one term at a time.

Urban – This is a system in an urban environment, namely a city environment with a high population density. Specifically, multiple agencies (notably the Census Bureau) considers areas that have a continuous population of over 50,000 and a density greater than 1000 people per square mile to be urban. A lot of places in the Unites States fit this description, but for our purposes, it’s areas that can be greatly improved by a centralized transit system – one where you can’t easily “park and ride” on the outskirts and get to the center with basic services and where driving a car in the dense center is problematic in terms of traffic and parking. For that reason, we’ll limit the conversation to highly dense centers with a land area greater than 1,000 square miles. This limits us to about 14 cities, ranging from New York to Seattle with all of the obvious places in between. This definition defines the extent (in terms of distance) the transit system would have to service, roughly 30 miles across. A system that covers more area than this would be beyond the scope of this discussion, and a system that serves a less dense area would be considered inefficient.

Mass – A great many. More specifically, it implies the ability to move a lot of people and for the service to be accessible to the majority of the population. On the first point, the capacity of the system must be on a grand scale. Rental scooters may meet the second half of the definition as currently implemented, but not the first part of the definition. The second point is critical, in that access cannot be dependent on expensive hardware (like a toll road requires a car) or usage cost and must be readily accessible (must start and stop in useful places). An express bus line with a single suburb stop may qualify for the first part of the definition but fails in the second part.

Transit – Fairly self-explanatory. A system of conveyance. But more than that, a functional system that is better than nothing. A subway system that moves slower than walking is not a transit system, it’s a ride. Similarly, a system of hired cars stuck in traffic is not meeting this definition.

Critical Attributes of a Good Mass Transit System

Gets you where you need to go

It’s pretty obvious that for any mass transit system to be considered “good” it has to go where you need it. That means that you can reasonably pick it up from your starting point and ride it close to your destination. “Reasonable” is certainly subject to debate, but we should really compare this relative to using a car. In a dense urban environment, finding parking near your destination (or even your residence) can be challenging. Any mass transit system that requires similar effort on either end (including quantifying the unquantifiable of the stress of finding parking) would be considered reasonable.

Cost Effective

For the transportation to be “for the masses”, the cost must not be prohibitive for the vast majority of users. It’s hard to determine what would be prohibitive, but let’s roughly calculate the cost of using a car. Gas is around $2/gallon, and for a rational car, that will take you about 20 miles, so that’s $.10/mile. Most cars cost around $25,000 and will last around 100,000 miles, so the equipment cost is around $.25/mile. Most cars have an annual cost of insurance, maintenance, inspection fees, etc. My experience tells me this all boils down to around $5,000/year, and most cars do around 15,000 miles/year, resulting in a cost of around $.33/mile. Adding it all up, you’re looking at around $.70/mile. This discounts major maintenance, finance fees, accidents, increase in insurance rates, etc. If an urban commute is on average ten miles, any mass transit system that costs less than $7/trip is cost effective and meets our definition. Note that this implies you can eschew a car entirely, so it’s a little rosy. To be truly egalitarian, the system should be cheaper to compensate, so a cost of less than half would be appropriate.


The first point would seem to fall under this category, but really this is the next level of discrimination. A mass transit system that requires pushers to get you onboard and runs every half hour technically meets the requirements of “gets you where you need to go” but could not be considered especially convenient.

Convenience is about whether it’s easy to use. That comes in a few factors: accessibility and availability. Accessibility is all about the physical interface. This includes ticketing methods, station layouts, cleanliness, crowding, etc. Availability is how easy it is to find the transport. This deals with the density of entrances and the periodicity of service. There is no real comparison with personal transport since in that case you have complete control over accessibility and availability (in the most part) given enough funds. Therefore we access appropriateness on a qualitative level.


Ideally a mass transit system would leverage the efficiency of scale and use less energy than a bunch of cars. Any mass transit system that causes more harm to the environment than the car alternative would be considered a very poor system indeed. It is generally accepted, that when compared to gasoline engines, this will be an easy wicket to meet, but with the prevalence of high efficiency electric vehicles, the gap may be narrowing.

Review of Current Approaches

There are essentially two approaches taken for mass transit. The first involves conveyances that operate on a fixed infrastructure, such as a track, tramway, or connected to overhead wires. The second is based on conveyances that have a generic interface with existing infrastructure, such as buses, scooters, or hired cars. We could talk about all of these, but the most prevalent of the two approaches are considered in this section for illustrative purposes. For fixed infrastructure, we will consider a subway system, and for existing infrastructure a standard bus system.


For our purposes we will consider subways as a set of trains riding on narrow gauge track powered by electricity. For my familiarity, we’ll use the New York City system (MTA) as a reference. This involves stops roughly every mile and trains that come about every five minutes. Let’s look at its critical attributes.

Does it go where it’s needed? – In the case of the MTA system, I find that to be pretty universally true. A lot of that has to do with the urban area. In a highly dense environment such as New York, the density of subway station stops is almost always higher than the availability of parking, making it generally better than a car for trips within the city.

Is it cost effective? – A trip is anywhere from $2-$3, which would meet the standard laid out. It would be nicer to pay by the mile since sometimes you want to stop multiple times, but even at two stops per trip it’s cheaper than using a car.

Is it convenient? – That’s pretty variable dependent on the time of travel, the train you’re using, and the stations associated. But more times than not it’s dirty, crowded, and you stand around waiting on a platform for a good bit. That means your trip might take a really long time and be uncomfortable to boot. It probably loses out on this metric.

Is it good for the environment? On this count, it probably is since it’s powered by electricity, and runs on a low rolling resistance rail system. Without specific analysis there’s not way of knowing, but I’m hard pressed to believe that the environment would rather have all of those people driving.


Since buses are pretty generic, we’ll assume the best on how the system is implemented in an urban area. That means some dedicated bus lanes, regular stops, and the use of hybrid technology.

Does it go where it’s needed? – Assuming good city and transit system planning, this should be a slam dunk. In an ideal scenario where mass transit is prioritized, buses can go anywhere a car can go, making this a flexible alternative and serving any area needed, even as demographics change.

Is it cost effective? – Generally busing is one of the cheapest forms of transit. The infrastructure is already available, so you’re only paying for the conveyance and energy.

Is it convenient? – Much like the subway system, this is highly variable. It has the same issues with being dirty and crowded. Unlike the subway, it shares infrastructure with cars, so often it has little control over schedule and can be heavily impacted by traffic. And the stops and areas where you wait tend to be less sheltered and more prone to weather impacts. It is therefore, on average, less convenient than a subway system.

Is it good for the environment? – In most cases a well maintained bus with modern technology with a moderate number or riders will use less fuel than an equivalent number of cars. But it stops and starts a lot (the most energy intensive portions), is not especially efficient (heavy vehicle on rubber tires), and is often not filled to capacity. A bus that is only moving two people is not going to be better for the environment than a couple of cars. And in traffic, buses idle just like a car, one of the largest sources of urban pollution (though hybrid systems have come a long way).

Some Currently Proposed Approaches

Beyond what is normally seen, there have been some innovations that could qualify for mass transit if properly applied. We’ll look at each of these as well.

Personal Rapid Transit

Initially this was envisioned as a system of individual tram cars that come on demand and take you directly to your destination. A hybrid of a subway system and a hired car service. It’s rarely been implemented due to a number of technical issues. More recent thoughts have considered the use of automated vehicles that use existing infrastructure – negating some of the technical issues previously encountered. That seems like the more promising approach, so we’ll look at that incarnation.

Does it go where it’s needed? – Assuming automated vehicles that drive on existing roads, it goes exactly where it’s needed and nowhere else. That said, there will have to be designated pick up and drop off spots, but they could easily be situated similarly to bus station stops. That’s pretty ideal.

Is it cost effective? – Since no real system exists, we have make some pretty big assumptions. Generally each automated vehicle is essentially a car, with the same fuel and maintenance costs. There might be lower insurance costs, but likely that would be offset by cleaning costs and premature wearing out of publicly used vehicles. It’s unlikely that the cost would be much different than the $.70/mile we estimated for a personal car, making this factor a wash. One could argue that the use of electric vehicles is an advantage, but I’ll note that fuel was a smaller fraction of the operating cost of a car than one would assume.

Is it convenient? – Most would imagine that this would be obvious. A personal vehicle that comes when you call it and only picks you and/or your party up. But we need to consider several factors. Dependent on the format of the vehicle, it may be too small to be accessible to those with wheelchairs or other such devices. And whether it’s available may be dependent on system demand, so it could be that you wait a while for a ride (imagine driverless Uber during rush-hour). One would think that it would be cleaner than a subway, but imagine all the things you see riding on a subway system. If the same people used these vehicles, why would they be neater all of a sudden (or smell better)? And worst than that, you’re stuck with whatever you get when it comes to pick you up, regardless of cleanliness, so you get to spend your ride marinating in the juice of the previous occupant. So surprisingly, personal rapid transit does not meet the standard for convenience.

Is it good for the environment? – The answer clearly depends. Recent studies on the ecological impact of hired cars (Uber and Lyft) have shown a large increase in pollution. But that was because they were “trolling” for riders. A coordinated system could be designed to be much more efficient. But you’re still moving tons of metal for a couple of occupants, so it’s likely that the energy usage per passenger will never be as good as a bus system, and significantly lower than a subway system.

Increased bike/scooter usage

Recently we’ve seen an attempt to democratize bikes and scooters in urban centers into a mass transit solution. The promise is there because they check off a lot of boxes: they use existing infrastructure, they can go anywhere, are compatible with the short distances of urban centers, are cheap to operate, and can only get but so dirty. So let’s dive in.

Does it go where it’s needed? – That’s tricky here. Once you have one, almost always absolutely (barring some local restrictions). But getting to one could be a wild goose chase. Especially in a high demand area during a high demand time. When you really need a bike or scooter, it’s pretty common that so does everyone else. If you can’t find one, there’s no way for it to go where it’s needed.

Is it cost effective? – This is almost certainly “yes”. The equipment is relatively cheap, the fuel is cheaper, and there is no infrastructure. Per mile it’s hard to beat.

Is it convenient? – It really falls off here. Certainly there’s no crowding, and as previously mentioned they can only get but so dirty, but you may have to wait around a while for the next one to show up. Add to that the weather. And trying to use it with a disability. This is a solution that only works well when the weather is good, and dependent on the location and time of year can be incredibly limiting. Add to that the danger and therefore good idea of having a helmet, this option loses a lot on the convenience factor.

Is it good for the environment? – Due to the low energy usage optimized for the size of the vehicle, it’s the most energy efficient solution on average. So yes, it’s good for the environment.

Addressing the Issues

Both subways and buses are primarily challenged because of lack of convenience. This isn’t about going where its needed (properly designed these systems can address that consideration), but crowding and traffic greatly impact the time effectiveness of these solutions. If there’s a complaint I hear most about mass transit it’s how much longer it usually takes. If we break down the reasons, the root cause is availability of service. Subway systems can come regularly during busy times, but they are very crowded, slowing down the onboarding and offloading process. Buses are often stuck in traffic, making you wait around a long time. In this situation, a personal rapid transit makes large inroads, though other factors make it potentially less favorable than current systems.

The next greatest complaint I hear is about cleanliness, or “ick” factor. It’s true that subway systems stink and are noisy. And you might have to encounter unsavory characters. But you can generally get away, either in another car or at the next stop. Buses don’t generally afford that kind of escape, but the format of the vehicle tends to discourage interaction, and the fact that people spend most of their time at the stop (not on the bus) minimizes the mess. In this case, currently considered solutions seem little better than what we already have. When there are that many people using the same resource, “ick” must be expected.

The final thing that could improve the current situation is make it more environmentally friendly and cheaper. Current solutions are up to this challenge but could certainly be improved. For subway systems this means a less damaging way (and cheaper way) to expand the system and do maintenance. For buses, this involves new technology and optimizing ridership.


It seems as though there is no concept of a future mass transit system that improves over the ideas we have had for decades. The real gain in the near term is to optimize the solutions we have and champion the use of mass transit. That leads us to our circular logic. For mass transit to be effective, it must be used by the masses and have a very high ridership. Until that happens, it’s not especially efficient or convenient, which will limit the number of people willing to use the system – especially if car usage is available. The conclusion is that the best way to improve mass transit is to get rid of the competition – limit car access to urban areas. This would force more people (many against their will) to use the transit system, allowing for it to run more efficiently, to more places, and with better service. Some places in the world have implemented means of limiting car traffic, usually as a means of pollution control. It’s not surprising that those urban centers have robust and widely used mass transit systems. In the United States, it’s unlikely that we could take that dramatic of an approach, which means that any mass transit system, unless significantly better than an automobile, is fighting at a severe disadvantage.

Short Plug

This topic has been on my mind for a long time. My number one pet peeve about mass transit is waiting around for the next ride, but when available I use it because I’m even more bothered by the energy inefficiency of piloting a car in an urban center. I don’t especially mind walking to the subway station, so if I could get on the second I arrived and not have to stop at in-between stations on my way to my destination, I’d be set. That led me to the moving walkway transit system concept that I’m patenting. Let’s do a comparison against the standards I set earlier.

Does it go where it’s needed? – At a minimum it mimics a subway system and even runs in the same tunnels. As an extension, the infrastructure required to support such a walkway is less than a subway system and could be used in above-ground applications and on surface streets.

Is it cost effective? – No formal study has been done on this metric, but the cost to outfit the “rolling stock” of the walkway is similar to the cost of a subway train line. The energy costs are likewise similar and may be lower.

Is it convenient? – Unlike current systems, there’s no waiting for the conveyance to arrive. It’s always moving. It also doesn’t stop at intermediate stops. There should be little crowding since there’s not pinch point (people enter the system when they arrive) and I suspect littering on a moving walkway is less likely than on a subway seat. Not to mention you can always walk away from unsavory characters.

Is it good for the environment? – I would imagine it would be the same as a subway system, but the infrastructure requirements are lower, therefore likely decreasing the ecological footprint of initial implementation.

I’d love to hear any thoughts. Rest assured that a lot more details will be coming out about this concept. And I hope to see you all on the rolling roads.

Dose of Aphorisms

If there’s anything this exercise has taught me, it’s just how a well conceived implementation of available technology can meet the transit requirements for urban centers. Granted it’s often poorly managed and planned, but the concept is still valid, even after all of these years. This brings me to today’s useless quip about valuing what we already have.

Sometimes the best solutions are those staring you in the face.

Explanation of Fields in the SMARRT form submission

Reference Scenario Inputs:

Number of People Infected – How many potential members of the gathering are infectious. The simulation starts when they enter (time=0).

Type of Activity – Impacts the number of particles spread as aerosols per respiration. More strenuous activities result in more viroid particles being released.

Air Changes per Hour – This is the air exchange rate with fresh air for the volume of air being breathed by the gathering. If you use forced air exchange, you can calculate the number of air changes per hour for your specific situation.

Space Floor Area and Ceiling Height – These are used to calculate the total space volume.

Duration Infectious Person is Present – This is how long the infectious person stays in the space after their initial entry. For the reference scenario, this defines the end of the simulation.

Gathering Scenario Inputs:

See the reference scenario for all inputs up to Time of space entry.

Time of space entry and exit – These values represent when you enter and leave the space referenced to the infectious person. For example, if you show up fifteen minutes late, but stay an hour after the end of a one hour party, the Duration Infectious Person is Present is 60 minutes, the Time of Space Entry 15 minutes, and the Time of Space Exit 120 minutes