# Is Green U.S. Transit a whopping myth?

As part of my research into robotic cars, I've been studying the energy efficiency of transit. What I found shocked me, because it turns out that in the USA, our transit systems aren't green at all. Several of the modes, such as buses, as well as the light rail and subway systems of most towns, consume more energy per passenger-mile than cars do, when averaged out. The better cities and the better modes do beat the cars, but only by a little bit. And new generation efficient cars beat the transit almost every time, and electric scooters beat everything hands down.

I encourage you to read the more detailed essay I have prepared on whether green U.S. transit is a myth. I've been very surprised by what I've found. It includes links to the sources. To tease you, here's the chart I have calculated on the energy efficiency of the various modes. Read on, and show me how these numbers are wrong if you can!

Note: If you want to comment on the cyclist figure, there is different thread on the fossil fuel consumption in human food which details these numbers and invites comments.

## Comments

### Mostly correct

These are indeed measured at different speeds. They are drawn from all travel. That is to say, they calculate how many passenger miles a transit system did, and they divide it by the transit system's total electricity bill, or diesel bill etc. So it's the full, realized average of all speeds. Cars are worse on city streets than the number here, which I point out, except the hybrids which are better than their average number on city streets. Ignore the bicycle number (it is based on something else.) The scooters are indeed a number based on the energy measurements of individual models, and of course only going at slower urban speeds. The main focus here is urban transit, and I would like to find numbers for all the modes that only cover urban transit.

### Some feedback

I think you did an excellent job of measuring the direct benefits of transit but you did a much poorer job of looking at the indirect costs and benefits of transit.

I don't know if you spent much time looking at this report.

http://www.nyc.gov/html/om/pdf/energy_task_force.pdf

or this one

http://www.city-journal.org/2009/19_1_green-cities.html

What stands out is that dense cities and dense parts of cities are dramatically less energy intensive on a per capita basis than more spread out regions.

Its not just that transit in Manhattan is dramatically more efficient than mass transit in say Fresno with much higher utilization rates, but people are also much more likely to walk to work or for shopping in Manhattan than in less dense place like Fresno.

If your primary means of getting around is by auto, than your city needs lots of parking for the autos. All of that space for parking means that more goods and services are spread out. That in turn leads to less walking in the neighborhood and a further need for more driving and less walking. That also means that your city probably will pancake out and never develop density.

Developement is path dependent. People taking transit aren't bring a car with them. That means that areas near transit corridors tend to end up being more walkable. That in turn means less driving in that neighborhood, lowering emissions. Areas with lots of rail connections tend to densify over time.

There are lags between the build out of the rail system and transit oriented development that follows. There are also network effects for transit usage. In the Bay Area, you have more transit villages and housing prices have risen higher near Bart stations than near the light rail stations in San Jose in part because right now Bart goes to more places, but also because Bart has been established longer.

With your robocar idea, my concern is that you are ignoring the high indirect costs of parking.

see here

http://www.uctc.net/papers/351.pdf

and much more throughly here.

http://www.amazon.com/High-Cost-Free-Parking/dp/1884829988

### Density

Yes, density does result in less energy use, and I touch on the other benefits of transit, which does indeed still have many. But it is not the transit that is causing the energy efficiency but the shorter trips, and the greater walking.

Robocars, as addressed in the Parking Article should not have a parking problem. They don't strictly need dedicated parking at all -- they can store themselves, ready for use, in all sorts of places you would not think of as parking, including the roads themselves. There is an almost exact correlation between how much spare road there is to how many vehicles are not currently moving. However, the ability for robocars to be re-used greatly reduces the number of vehicles needed and how much time they must spend stopped. If the vehicles are 1/3 size, it is further reduced. If they are all tight parked, valet-style, it reduces it again.

### A couple of points

First light rail projects tend to increase property values (and thus property taxes) in areas where they are built. I think that is an indirect benefit that has the effect of cutting the cost of building out light rail systems. I also think more of that benefit could be captured if funding for light rail systems was shifted away from the feds and onto transit benefit districts where property owners in the areas adjacent to the light rail systems were expected to contribute a greater share of the costs of the system based upon their proximity to the light rail stations. Part of the cost of light rail is really a transfer payment from the feds to property owners along the rail corridor. If that subsidy was eliminated, by shifting the cost from the feds onto property owners adjacent to the project, I suspect the cost of building out rail systems would drop significantly.

http://www.apta.com/research/info/briefings/briefing_1.cfm

Second as you acknowledge increased density decreases trip lengths and increases walking. But the point I think you are missing is that one of the things that can is drive increases in density is the buildout of these rail systems. The rail system increases property values and developers respond by putting more units in these projects. The bigger the rail network, the more property values near these lines increase and thus the more these transit oriented developments start to pencil out. Which leads to further increases in density. Look what happened in Walnut Creek or Concord since Bart came to town. In the areas near the Bart station, not only did you have access to the local labor market in Concord or Walnut Creek but also to a lot of the people living near Bart stations. This is why that land is worth more and is more productive and used more intensely than in other parts of these towns.

With your robocar proposition, because there is no fixed entrance and exit point, I am not sure local property owners have the same incentives to build densely the way they have incentives to build dense projects near transit stations. That means less density, less walkable neighborhoods and less walking. Also because there is no specific geographical benefit area, you can't create a benefit district to offset the cost of running the project.

Look at the really dense places. They all have very thick dense rail networks to get people in and out of them. SF has Bart, Caltrain, Muni and the Capitols. There is even plans to put the high speed rail station in SF. In NYC you have the NYC subway system, plus the regional rail systems like the Long Island Rail System. In Chicago, all of the CTA trains converge in the Loop, plus you have a series of commuter rail systems bringing in people from the suburbs.

As Los Angeles MTA started building out its rail system and connecting it into downtown LA the downtown area has seen a revival. I suspect as the rail connections thicken into downtown LA, the more that area will Manhattanize.

With your Robocar idea, I think it will encourage more of what has been described as dense sprawl here

http://ecow.engr.wisc.edu/cgi-bin/get/cee/970/wittwer/3-03densesprawl.pdf

and see discussion of percieved/weighted density here.

http://austinzoning.typepad.com/austincontrarian/2008/03/perceived-densi.html

and here.

http://austinzoning.typepad.com/austincontrarian/2008/03/perceived-densi.html

Note how Austin has higher standard density than Boston, but Boston has higher weighted density. Boston also has higher levels of transit usage and greater levels of walking. Similiarly LA has higher standard density than NYC, but NYC has higher weighted density than LA, NYC also has a much greater transit utilization and people are much more likely to walk to work as form of transporation.

Why this matters is generally speaking the places with high weighted densities generally have the highest city/suburb difference in CO2 emisssions. Where as the places with dense sprawl do less well than the places with low weighted densities or dense sprawl.
(See table 5 on pg 44 here).

http://mek1966.googlepages.com/w14238.pdf

CO2 emissions are lower in the bay area because the climate is mild and because the local power sources include a lot of hydro, wind, geothermal and nukes. But emissions are much less in SF than Santa Rosa because people in SF walk a lot more and drive a lot less.

In the hierarchy of emmissions. High density sprawl is better than low density sprawl, (you are more likely to find and use transit in LA than Fresno) but high weighted density areas do much better than high density sprawl areas (you are more likely to use transit in Manhattan than in LA and the transit system is much more likely to be highly utilized in high weighted density areas).

### Density and the mode of transport

I would not disagree that rail systems (or other transit that has stops) will encourage density.

However, I can't see any rail system competing with a robocar system. If you can summon a vehicle and it shows up at your door/garage/elevator lobby in under a minute, and then takes you effectively nonstop to your destination in comfort and privacy (and efficiency) customized to you with space to work, read, watch or use the computer, at a price competitive with the transit, then how can the transit compete with that? Transit where you must walk to a stop, wait for a vehicle, ride it while it starts and stops, possibly having to stand or sit in a cramped seat next to a malodourous neighbour? It can't. Not even remotely. Even if the robocars were not competitive on efficiency and were triple the price, I don't see the transit being able to compete.

The only ways the transit can compete would be over longer hauls where express trains can go faster than private vehicles, or through the use of private right-of-ways that bypass the congestion caused by human driven cars. Once the human driven cars are gone (which is some ways away) this advantage is lost. Indeed, even before that, the robocars on private right-of-ways can also bypass the congestion.

So while we might have an academic discussion about whether transit would increase urban density and whether this is positive, it seems like an entirely academic discussion -- at least if you conclude the robocars are coming. If you don't think they're coming (not even on private rights of way) then you can have the discussion.

### "However, I can’t see any

"However, I can’t see any rail system competing with a robocar system. If you can summon a vehicle and it shows up at your door/garage/elevator lobby in under a minute,"

You're fantasizing.

If you have the volume of passengers to actually implement guaranteed under-a-minute arrival, you have the volume that you need mass transit due to congestion.

Otherwise, you face the problem that if (say) three other people in your neighborhood call for cars, the car for *you* has to be summoned from a great distance, and will take quite a few minutes to arrive.

### Do these figures take into

Do these figures take into account the fact that traffic congestion decreases the efficiency of private cars?

### Congestion

The figures calculated from the DoE are, as far as I know real world figures. For example I think for a transit agency they calculate its passenger miles and its fuel bills. For cars you would need to dig deeper for the methodology, but I believe they are based on real world mixed mpg figures, which include travel in congested areas. The ideal method would be to again get a sampling of cars and calculate their passenger-miles and their actual gallons of fuel consumed, I don't know if they have done this. Refer to the energy fact book for details on their methodologies and how they have changed over time.

### They're real-word figures,

They're real-word figures, but the issue is that they're national averages of both high-congestion areas which often have a transit option, and low-congestion areas which often have no transit option. Cars in high-congestion areas have much, much higher BTUs/pm than the national average given in those tables. For example, in New York City, the average is about 8000 BTUs/pm for cars, compared with about 3200 BTUs/pm for the current bus fleet, making bus transit unquestionably a greener option than cars.

### Efficiency and congestion

It is correct that these are averages and that you would want to find the numbers for a particular city to make a comparison.

However:

• Hybrid cars, like the Prius, actually get better city mileage than highway mileage, because they handle stop and go much better with electric operation and regen breaking. So they still beat the bus.
• Electric cars are even better at this.
• My main surprise is researching this data was that the transit was not several times greener than the cars. Learning that it is only modestly greener is better news, but still quite surprising. Particularly when we know the newer cars are doing better.

What's the source of the 8000 btu/pm figure for NYC? That's 15 mpg for a solo driven car, and 10 mpg if a 1.5 passenger average is used. That's pretty low even for city driving, I think. Many cars do now report real-time MPG so I would be interested in calculated "total trip" MPGs for typical trips in NYC and other places. Remember that while we only want that particular city, I want to cover the entire day, including the fast, congestion free trips outside rush hour, and both the slow and fast parts of rush hour trips. A good way to do this would be to get reports from people who drive around the city in various patterns, and record gallons purchased and total odometer travel.

Note that a city bus is also horrible in stop and go traffic. A dedicated ROW vehicle like a subway has its best win at rush hour. My figures show that buses and street cars often pull more weight per passenger than cars, other than when fully packed, and sometimes not even then.

### "What’s the source of the

"What’s the source of the 8000 btu/pm figure for NYC? That’s 15 mpg for a solo driven car, and 10 mpg if a 1.5 passenger average is used. That’s pretty low even for city driving, I think."

Ever driven in Manhattan? I can believe it. You rarely exceed 15 miles per hour and spend most of your time idling. Electric vehicles are a big help here because they use so much less energy when idling, but the subway's a faster trip anyway. And this isn't "at rush hour", this is practically any time except 2-3 AM.

"Note that a city bus is also horrible in stop and go traffic. A dedicated ROW vehicle like a subway has its best win at rush hour. My figures show that buses and street cars often pull more weight per passenger than cars, other than when fully packed, and sometimes not even then."

The "common wisdom" among transit planners nowadays seems to be "if you can't get exclusive or nearly-exclusive ROW, don't bother," for core lines, anyway. (Feeder lines and "subsidy for the poor" lines are judged differently.) If mass transit is to function as congestion relief it needs to have ROW separate from the low-occupancy vehicles, period.

### Light Rail & Transit System

Your numbers make some light rail projects (like Salt Lake City) look very good. However, you should consider system-wide effects. Basically, the SL rail system replaced the most heavily used bus routes. Other bus routes were reconfigured to feed the light rail system. Light rail looks good, but the bus system looks much worse after adding light rail to the system. Adding light rail may have actually reduced the energy efficiency of the public transport system.

### You are correct

According to this spreadsheet extracted from the National Transit Database Salt Lake's light rail is good but the motorbus number is 8500 btus/pm, for an average of 5400 btus/pm, about the same as the average solo car!

This is one of the debates we see in light rail, and even commuter rail, whether the rail and feeder approach is energy efficient. It certainly isn't very fast, it's unusably slow if you want to go between two points that are both not on the rail line.

San Jose is the reverse, by the way. The light rail is worse than the bus but the overall average is 5500 btu/pm, again worse than the cars. In San Jose's case, there really is not much of a feeder system, and the light rail stations themselves are often not near anything -- neither businesses or houses -- once you get outside the downtown core. The whole southern system was built along the middle of the freeway, so nobody is a convenient walk from the stations.

### Aptera 2e

They are claiming 80 Wh/mi for the Aptera 2 and they claim they can do that at 55mph. That works out to 272BTU/p-m (solo).

http://aptera2e.org/aptera-2e-specs/

### Not quite

DOE calculations are done fuel to wheels, so one kw-h is 10,300 BTU, so 80 watt-hours is 3 times that figure. This is based on national average grid power.

### It's the density, ...

It would be interesting to dig out comparable figures for other "cities". (San Jose is a town which annexed way too many subdivisions.) I'm a native Chicagoan, and take the city buses and trains everywhere. Late at night, there may be very few passengers, but overall, I expect the efficiency figures are way different from San Jose's.
But this is only one facet of a national strategic problem I've wondered about for a while. Since WW II, the infrastructure of the United States has been largely expanded or rebuilt around the single-passenger automobile. Now that the cheap oil is gone, we need to move to more efficient transport. But efficiency depends critically on density, and the "normal" suburban density can't support public transit. The outermost suburbs will become slums or abandoned as gas prices continue to rise, but I don't see good strategic options for increasing population density. You can't really infill quarter acre lots.

### Efficiency and density

Density does increase transportation efficiency a lot, however, there are other ways to be efficient (lightweight electric vehicles, road convoys) that not only can handle our current densities but in fact may generate more sprawl if we are not careful. I don't thnk the burbs will waste away.

### The burbs may not waste away

The burbs may not waste away entirely, but there are already entire abandoned foreclosed subdivisions outside of LA.

And as for "our current densities", we have many current densities. Road convoys and lightweight electric personal vehicles aren't going to handle Manhattan densities or Boston densities, but would have no trouble with San Jose densities.

### it would be helpful if a

it would be helpful if a publication date is included with the article; i viewed it at:

http://www.templetons.com/brad/transit-myth.html

and realized that i had no idea when it was written and that in the future this would become murkier...

### and also, oops, forgot to

and also, oops, forgot to share, a couple radical views which at the least may provoke a chuckle or two...

i say burn all the oil we can as fast as we can and get it to run out as quickly as possible to force markets to alternative fuels with the dual benefit of green savings and independence from foreign entities not beholden to our interests. take away their bully pulpit, as fast as we can and i see the tank running dry before real solutions arriving. the more quickly that tank level drops, the more quickly will be seen automobile conversions to LPG fuel, carpooling, transit use, etc.

additionally, it only takes a single "breakthrough" to bring marketability to hydrogen fuel systems, or hydrogen fuel cells, or whichever field strikes gold first. there are so many damned alternatives out there and so much effort spread between them it's hard to say which will strike it big first, but i feel it inevitable one will, likely before we run out of gasoline...

### Don't want to burn it all

First of all, burning it all would generate huge amounts of emissions.

Secondly, I am a peak oil skeptic. There are arguments pro and con, but I have a strong (and well back) optimism about human creativity when faced with a problem like finding more oil where they said there was none. Obviously if it is not there we won't find it, but there's not too much evidence of that. The amount of unexploited tar sand in Athabasca is immense, but messy to get out.

So if we burned it all, we would just find more.

Breakthroughs are coming, though remember that hydrogen is not an energy source, it is an energy storage method, like batteries. And right now, not a particularly dense one, though we might well fix that.

And as for publication date, this blog post has one at the top, June of 08, which is about when I released the article. Of course the articles change with time.

### One version of peak oil: It

One version of peak oil:
It doesn't mean that the volume of oil extracted per year will necessarily peak (though it is likely to), it simply means that the real price of oil is going to go continuously up from here, apart from short-term fluctuations. This seems to be fundamentally correct -- the cheap oil era is over and over for good.

Of course, what that means is that oil becomes poor return on investment compared to solar/wind/electrical/hydro/coal/whatever, and so people stop putting money into extracting it for fuel, so the total volume extracted drops and the investment in extraction drops, and then you get a feedback loop driving money away from oil.

It's still a great feedstock for plastics -- if I were running a 50-year investment and I had the capital and political ability, I would tie up some good, easy-to-pump oil fields and refuse to extract anything from them until after oil was abandoned as a fuel. Then I would jump back into the market as the lowest-cost producer of oil for plastics and make a killing.

### Cyclists

Fat people in cars eat as much if not more than people who exercise bt commuting. My food consumption goes down when I exercise, not up. I also happen to be a vegan, so even better.

Get it straight.

Now, for questions:

In your considerations have you included the massive subsidies and incentives government has infused into the auto industry that is fast becoming a zero employer due to automation? Seiously, the costs, both financial, environmental and social, as well as the innefficiency of private over public and human powered (cycling, running, walking, etc...)transit is ridiculous to dispute. What is in dispute is that a society that, by this time, should realize it has responsibility to future generations still acts with the ignorance of the past. The only difference from the past is that such ignorance is fast becoming willful and dangerous.

### You miss the point of the article

It already says most of the things you say -- better to be vegan, we all need to exercise. The article is about how fuel-inefficient U.S. agriculture is, so inefficient that typical Americans are getting lower mileage than the car. It's about agriculture.

However, the efficiency of private and public transportation is another matter. It's the government's own figures that show the public transit doing so poorly.

### carpooling

You may be interested to know that there is a well-established system of carpooling to and from Washington DC and northern Virginia.

http://www.slug-lines.com/

Because it requires at least three passengers per car, a car of "sluggers" is quite efficient.

### Just a starting point for energy analysis

I think this shows simply the importance of designing a good, heavily-used transit system rather than a bad one.

San Jose VTA has become a bit of a poster child for "badly designed".

As an important point which you touched on tangentially: When you figure in manufacturing costs, rail transit will look better compared to cars (and possibly even scooters), because the vehicles have less steel per passenger than cars (and possibly even scooters) and last significantly longer (50 years for some transit vehicles, though 30 is more normal; 5-15 for cars, unfortunately.)

### As the numbers are not far apart

Because the transit numbers and car numbers are within reasonable range of one another, it is not really important to consider improvements in transit which are not on the order of doubling or quadrupling the efficiency (or ridership with same energy.)

For people to ride transit as the green choice, it is not enough for them to save 20% or even 50%. That's because in the USA in most cases, riding transit is a big sacrifice in time, convenience and other factors. Transit can be more convenient in a few cases, like private ROW in a congested rush hour (when it is also efficient) but outside those cases, people are already willing to spend tons more money for private transportation. They will not accept the inconvenience of transit just to be a little greener. They want to be 4 to 10 times greener, and it's very hard for transit to deliver that.

### Public Health and the true costs of Parking

Brad,
You point out that there are considerable external costs and benefits to both auto-centric transportation and transit-centric systems. You also seem to recognize that it is impossible to speak about transportation without also discussing its relationship to land use. What do you say to those who see transit as an important component that enables safer, healthier, more livable communities? Wouldn't you agree that encouraging compact, walkable, transit oriented communities is an attractive way to reduce the need to supply copious amounts of parking which is expensive at \$2-3 thousand a space for surface lots and about \$15 thousand per space for structured parking to construct, not including long term maintenance. According to Donald Shoup's book The High Cost of Free Parking, the economics of free parking is what drives our destinations further and further apart.

What are your thoughts on the effects of an auto-centric environment on public health? Some connections are obvious 4,000+/- pedestrian deaths each year in the US, 40,000+/- annual deaths in motor vehicle crashes...
(http://www-fars.nhtsa.dot.gov/Main/index.aspx)

other connections are being made by health professionals between health and our built environment:

365,000+/- annual deaths due to sedentary living (Mokdad, A.H., et al. 2004. Actual causes of death in the US. JAMA 291: 1238-45)

\$40,000,000,000+/- direct cost to tax payers due to inactivity and poor nutrition. (www.cdc.gov/nccdphp/dnpa/
(Obesity Research, Finkelstein et.al., Jan, ’04)

It appears that the best way to help people get the recommended 30-60 minutes of aerobic exercise per day is to create an environment where they get that exercise without even noticing it, for example: walking to/from work, school, or a transit stop. To make this lifestyle feasible it requires destinations to be within close proximity. Transit oriented density makes for a much more livable environment when compared with auto-oriented density (places like Los Angeles which has the density of a city but the relative parking supply of a suburb). To that point, fixed guideway transit is the only way to send a clear message to private developers that it is okay to reduce their parking supply because the presence of the transit infrastructure signals that service will continue. (Bus routes can change overnight, but its hard to re-route a streetcar)

On the earlier discussion of infrastructure funding, I agree that we have a pretty dumb system in America. The Barchan foundation has done an excellent job of analyzing the way that the world's infrastructure is paid for, and I would be for a system much like much of the rest of the developed world uses where contracts for public asset for design/build/operations/maintenance are bid together as a package instead of separately. (You'd design and build something very differently if you were the entity that was ultimately going to have to create a system to fund the operations and maintenance of that asset.)
http://www.barchanfoundation.com/

I only propose this approach for urban developments were the market can be supported, and mounting evidence suggests that generational preferences in the U.S. are shifting towards a more urban lifestyle.
http://www.rclco.com/pdf/Gwinnett_Redevelopment_Forum-Gregg_Logan-8-10-09.pdf

Transit is not especially viable for rural areas and by accommodating new population growth in an urban form we can ensure that those great rural areas stay rural, let rural residents drive robo-electric vehicles, but keep them out of the city, we don't want to inflate our costs of living by having to provide parking garages.

### No robo-electrics in the city?

That's entirely backwards -- you want people to drive gasoline cars in the city? You're not going to get a walk&transit-only city, not in the USA, not even in Europe. There are still tons of cars on the streets in Manhattan and London and even Tokyo and Shanghai. I've seen a few Asian cities where the cars are rare like Hong Kong but this is both unusual and often a product of geography.

There is only so much you can do, or want to do, it forcing people to do what you think is "best for them." It is far more effective to offer solutions that they think are better, which also meet your agenda. Well, not just far more effective, because it's binary. It works, the other one doesn't.

You can figure out what you want -- healthy living, pleasant environments, quick trips, serendipitous meetings -- but it doesn't work to tell people how to get it. You always get it wrong. People want these things and you can arrange so they can get them when they want them.

Robot cars of course do not require garages in any significance, and where they do require garages they don't require them to be in the expensive or concentrated areas. (The further away they wait, of course, the longer they take to summon and the more energy they use, but they are so efficient that a few miles doesn't hurt and if you just want the next available taxi you don't have to wait because most of them are stored 2 miles out of the CBD.)

### RE:Public Health and the true costs of Parking

Come on Brad,
I was hoping for a little more than just and antidotal response. You're correct that there is not much that can be done to get people to adopt healthy lifestyle routines that scientific research says are good for them. That is partially due to the reality that the suburban, auto-dependent environment we have built in america for the last 50-80 years is not conducive to a convenient healthy lifestyle. When I flash forward to a future full of automated personal vehicles a few scenes from the movie WALL-E come to mind. I also realize that there is very little that I can do to cure cynicism. What I can do is chose to live in an urban walkable environment, design compact walkable communities, and vote to support policy that favors transit and transit oriented development. It only took one human lifetime for us to make a mess of our cities, maybe it wont take us that long to heal them. You probably wont be around to see it, but maybe I will.

### It's hard to vote it in

What I mean is it's very hard to vote in lifestyle changes. People do what they want to do regardless of what the government tries to make them do. The challenge is to avoid the wall-e world by making it less attractive, not by outlawing it.

### Not as hard as you might think

Don't get me wrong, consumer adoption of new technology, mainly widespread car ownership had a substantial impact on our built environment. But, we voted transit oriented communities OUT when we allowed policy changes to occur at the federal and local level that favor auto-oriented development. If you read Fighting Traffic by Peter Norton (http://www.amazon.com/Fighting-Traffic-American-Inside-Technology/dp/0262141000) you’ll see that it was not an easy battle for the motorist lobby to win. I’m not old enough to remember, but you may recall “Urban Renewal” projects in the 1960s and 70s where we took a good idea: the interstate and DEFENSE highway system (originally envisioned as a way to rapidly transport our military to any point on the mainland and facilitate the movement of goods) and made the bonehead mistake of deciding it should become the backbone of personal transport in this country. So we carved wholes through our neighborhoods and constructed monstrous concrete and asphalt barriers in the name of progress and fragmented our cities in many cases accomplishing the very opposite of the program’s goals.

Today we continue to subsidize driving by spending 40 billion dollars a year on highway and roadway infrastructure while most local municipalities collectively mandate billions more dollars a year in construction and maintenance of parking facilities through minimum parking requirements (basically a driving subsidy yoked to new development). Never mind that we haven’t been paying the real cost of this infrastructure, the ASCE gave roads a” D-“ this year, estimating we need to invest 930 BILLION dollars, just for roads, over the next 5 years, just to make up all the deferred maintenance and get back to an “OK” level of safety and service. http://www.infrastructurereportcard.org/fact-sheet/roads

The original streetcars that were present in almost all small and large American cities at the turn of the last century are almost non-existent today, not because they were an inferior mode of transportation, but because most of them were built and operated by private companies and continued to be taxed while our government pumped huge amounts of money into the largest construction project in human history (China’s Great Wall might as well be a sandcastle compared to the US interstate highway system) and subsidized driving by mandating minimum off-street parking requirements. Ask any economist what happens when you tax one competitor and subsidize another, the one being taxed loses every time. I’m part of a broad and growing coalition that is working to make policy changes NOW because I know it will take a long time to address these infrastructure issues and I don’t want my kids and grandkids to still be dealing with this by the time they are in my shoes.

### It's not that easy

Indeed, many of those things happened. But I am afraid that people have come to love the personal car lifestyle without government pro-car regulations and subsidies to help them. And in many cases, those pro-car rules were passed with the glowing support of the people. When traffic is congested and parking is hard to find, people do get frustrated with their cars, yet they still demand their cars even when they understand their true cost, which can be many times more than the cost for non-owners. People will pay many times more for door-to-door, no waiting to start convenience, the ability to carry stuff with them (and leave it in the vehicle) and not having to sit next to random strangers and homeless dudes. They want that even when the transit is faster, but in the USA it rarely is; the transit is often much slower, sometimes even an order of magnitude slower. Even in cities with great transit like Tokyo people wish for cars and will pay a fortune to have them.

But robocars will replace transit because they could fix just about everything people prefer about transit, except transit's ability to avoid congestion when it has private right-of-way. But that's not a virtue of transit, it's a virtue of private right-of-way, and if we need to, streams of robot cars, jitneys and the occasional van on private ROW will provide people with the best of both worlds. I don't think we'll actually need to.

People can use this tech to be much more efficient than today's transit systems or cars, but some will also use it to be more wasteful (by living further away because the trip is so pleasant.) But we won't stop them from doing what they want to do, not very easily.

### Galveston Light Rail..?

Your data source is flawed, simply put Galveston DOES NOT have light-rail, it DOES have a diesel powered replica trolley that IIRC was damaged by hurricane IKE, it is NOT a very good example of light-rail, why not try Houston (Which likely data was not available for when this dated data was collected)..

The Galveston trolley's capacity is more along the line of a city bus, where Houston MetroRail cars have a capacity of 220 passenger per unit & the single operator can operate two units by MU, with computer remote control. That one operator can carry more passengers than buses, as typical transit buses max out at 50 passengers with standees & that one 2 car articulated train can carry 440 passengers at peak travel times..

TRE Trinity Railway Express in Dallas & Fort Worth can carry closer to 800 passengers per scheduled trip in a multiple car bi-level consist with conventional passenger diesel locomotives that are geared for commuter rail speeds on a route that is 35+ miles long..

Get real, get data from APTA on ridership in the many forms of transit they represent from buses to the New York City MTA, which operates more passenger rail cars than any company in the USA.. (New York MTA includes 3 bus systems, subways, Long Island Railroad (The oldest US railroad operating under it's original charter), Metro-North which operates from Manhattan to Connecticut & on a line in New Jersey to parts of New York along the New Jersey/New York state border, as well as a line running North along the Husdon River..

Howard Bingham, Houston, Texas

### Light rail chart

Is from the DoE's energy book, based on government sources. Is the Galveston trolley on rails? Rail service is not judged on how it is powered, it's just whether it's on rails. Light and heavy is a measure of capacity, not weight, so an 800 passenger vehicle would be heavy rail.

I am always interested in more sources of reliable data, ideally from independent research. The numbers range a lot, so I am sure there are various factors which should be adjusted in many of them, but the general ranges do lead to the main conclusion -- that the energy efficiency of the various transit modes is similar to the car average, and that it's a very rare system to beat it by much.

That says the focus should be on those very good systems, and on more efficient private vehicles, at least if it is the maximum efficiency you seek. Congestion is an independent issue.

### Public transport versus cars and scooters

Why can't you move to metric units? 90% of the world only understands metric. I am British so I still vaguely understand your units.

So far as I understand your argument, it is far less valid in Europe and Japan, where some inter-city trains run with a 80% load factor (as high as planes) and some countries' electric trains consume less source energy than a small diesel car (both quoted at the average load factor of about 33%, not the peak load factor).

Also, if trains were allowed to be as flimsy and unsafe as motorcycles or scooters, the energy consumption would probably plummet. New trains are strong enough that most passengers are likely to survive a head-on collision at 100 km/hr (60 mph. In some ways this is an absurdly high safety standard compared to cars let alone scooters. In occasional British train accidents at 150 km/hr, there haven't been that many deaths.

So why don't you make buses and trains lighter and save 50% of the energy? From my visits to the USA, I think you've developed such sprawl since WW II that this explains much of your problems in making public transport work. Putting buildings far apart actually makes it necessary to use cars to get to them. That in turn makes public transport less viable. If you visit a European city such as Amsterdam or Zurich you see the opposite tendency.

Regardless of energy use, I can't see battery electric vehicles making huge progress unless we see a battery breakthrough. We've been waiting/hoping for one for decades, if not a century. Lithium-ion costs more than lead-acid (although it's lighter). The promised savings on fuel (mainly because electricity isn't taxed and diesel or petrol is) are set to be more than offset by extra costs of leasing batteries (or occasional huge expenses of \$10,000s to buy a new battery pack).

### It's better in Europe

It is better in Europe, and even better in Asia, but on the order of twice as good, whicn is actually not that much, and not as good as ultralight personal vehicles.

Mass transit vehicles could be made lighter and more efficient, it's true, and in the past there has been no big incentive to do so, but that may change. But this doesn't alter one of the other issues. Sharing is more efficient, but the starting and stopping, and indirect routes of sharing are not. And the required below-average loads (you will never get a system that's always full) are also inherently inefficient.

Ultralight vehicles only use their energy for the actual trip. They only run empty, if they do that, for short repositionings.

However, they need either the battery revolution, or robocars. Both appear to be coming.

### Other figures to contemplate

When we choose to drive, we are adding our car to the existing transportation modes in operation. Jumping on the bus doesn't add significantly to the fuel consumption of the bus, but it will run whether or not we get on.

Therefore, the BTU's per PM figure for a car should be added to the figure for the bus, train, or other option not chosen, like this:

1. Bus --4300 BTU/PM
2. SUV + Bus --8200 BTU/PM
3. Electric car + Bus --6400 BTU/PM

It's not as if we can cause the bus to stop running by not riding it. We can only choose not drive our own car.

Another concept to consider is the efficiency of highways vs. train tracks. For medium-distance rail from suburbs to cities, the trains use only a set of tracks which require very little maintenance over many years. Cars require a highway with 2-4 lanes on each side, the surface of which needs to be periodically replaced at a huge expense.

It seems to me that in your effort to promote robocars you've done a disservice to mass transit modes by selectively using the statistics and underplaying the value of increased ridership and economies of scale. Recycling plastic, for example, is inefficient on a small scale, but at a certain critical point it becomes profitable. It would be more so if the environmental cost of plastic were embedded into it's retail cost.

City buses would benefit from hybrid technology, which would mitigate the inefficiency of their frequent starting and stopping.

I think your use of the 1.57 passenger average figure is misleading. When most of us make a commuting choice, it is not with 1.57 people in mind, but simply ourselves. Your figures for car efficiency should be based on 1 single passenger. There is no such thing as 1.57 passengers. If and when we consider taking another passenger along with us, then we can simply make our decision based on nearly doubling our efficiency, etc.

But again, that is subject to the fact that the bus or light rail would run with or without us, so we must add our car's energy use to that of the bus.

It seems to me that you've gone out of your way to trash mass transit. The fact that you've ridden it or your bicycle doesn't absolve you of that.

The very same stats can be interpreted to show a brighter future for mass transit, and I think it would help our country more for you to use your considerable researching skill and efforts to that end.

### This misses the point

As I say, adding yourself to any vehicle (carpool or train or bus) that is already going is indeed the efficient choice, but these numbers are based on what happens in the real world, among people who by and large know that. Saying, "Transit would be more efficient if people would only ride it" imagines we have a magic wand that will make that happen. People take the path that is cheapest and most pleasant and convenient for them, and I don't see much success in changing that.

Our task, if we wish to plan for an efficient future, is to implement the most efficient forms of transportation that people will actually choose. Building a system that would be efficient if people rode it, but which people won't end up riding is not the green thing to do. It's actually anti-green.

And yes, the bus does stop running if people don't ride it, at least if the bus system is rational. No single rider or non-rider makes that happen, but in aggregate they do. Many bus systems are not rational of course, they don't even go so far as to run a smaller, lighter van as demand drops.

Of course cars should be measured on their occupancy. That's what the transit is judged on. But your argument that we must add the energy of the bus we didn't ride to the energy of what we did ride makes no sense to me. This is not about individual rides, it's about how to plan what to build.

Yes, roads do use more energy to build and that is a factor I would like to get good numbers on to include in calculations. And yes, buses should definitely be hybrid and perhaps some day they will. But cars, as they go electric and hybrid are getting better even faster, due to the greater rate of innovation you always see in small personal products compared to big institutional ones.

But my main difference is your attempt to disparage my motives. My goal is to try to figure out what we can make efficient based on what people will actually use. Many seem to come into this saying, "transit is clearly better, and if it's not efficient enough, let's try to force it to be." I think we should end up deciding what is better by factoring in the final results, and not just the theory. Right now, based one what I know people want from their transportation, the robot cars, once implemented, offer the best combination of meeting that demand and being efficient, though even that is not assured. Transit's long history does not predict much success here. The history of cars would not either, if it were not for the fact that now people are looking to buy more efficient cars, cars 2-3 times more efficient than what they had a few decades ago.

Will we ever get transit ridership and service in the USA to match that in places like Japan? Past history indicates not, but even the fine Japanese transit doesn't beat the potential of ultralight cars as enabled by robotics.

### HIGH SPEED RAIL

I think the author or someone on the same wavelength (I almost wrote "wavelink") has commented that using smaller, lighter vehicles designed for much
slower speeds would improve energy efficiency a lot. That sounds reasonable to me. But I note that the very high speed Japanese "East" line rates excellent. Do the laws of physics (where I think resistance increases proportional to the square of the velocity, something like that) get bent with high speed non-levitating trains? obviously I can see that a long train presents a proportionally small area to atmospheric resistance but I would expect that friction to be a huge factor. Any comment?

### It's complex

Energy loss comes from 3 things mainly -- engine inefficiency, rolling resistance, and air drag. Long trains have low air drag per person (when fully). Steel on steel and maglev are very good for rolling resistance. Maglev is of course super good.

### Flawed Fundamental Assumption

Your numbers assume that all occupants in a car are passengers. If the driver is operating the car to "pick up the kids at school" or "drop off the spouse at the airport," then they themselves are not a passenger, and the car has exactly zero passengers for half the trip.

You're including potentially empty subways while assuming taxicabs are never without a fare.

How do the numbers compare if the driver is only truly a passenger, say, 80% of the time?

### Chaffeurs

Yes, I suspect this error is present in the DoE's numbers. However, I am curious if you have information as to what the magnitude of the difference would be, ie. what fraction of total road travel is "support" like cabs. In Manhattan the value would be quite large but in most other cities I don't see the cab volume as super high, and it's quite minimal on the highways and suburban roads.

One can debate if transporting the kids counts, since the parent is not just driving, but supervising the children. Now I personally agree with those who say we over-do this and young kids should be able to ride transit from school (in the cases where it exists) and I certainly rode it when I was 9, but most parents are not this way.

However, that's beside the point because my guess is this does not tweak the numbers a great deal. You say it's a fundamental flaw so I presume you have numbers to show it's much, much larger? I do expect (or hope) that people will be more willing to trust children to a robocar, with a constant videoconference link back to a trusted supervisory adult for the ride. But that's for the future.

### Once you get to a certain density, cars can't work.

As far as public transport vs cars, there are cases where cars could not possibly provide the service, regardless of energy efficiency. For instance, on average in 2007 the NYC subway system transported 388,802 people into the business district of Manhattan between 8am and 9am. To get the same with cars would take at least 167 inbound lanes of bridges and tunnels.

http://frumin.net/ation/2009/08/whats_capacity_go_to_do_with_m.html

### Road capacity

Road capacity is actually quite large. I am working up some articles on that. It would not take 167 inbound lanes with robocars. That's a number for today's cars.

Imagine the cars were just 4' wide and 10' long, and ran on a 1 second headway instead of the 2 second headway we try with regular cars. That would be 54 regular sized lanes, which still seems like a lot, but in fact if you don't have cars parked on the side of the road a typical "2 lane" street actually has 4 lanes, so it's just 27 ordinary streets if you can redirect at rush hour, and clear away at rush hour. And just 18 of the "2 lanes each way plus one lane for parking" minor arterials, which most cities do have going in, though Manhattan is of course unusual as an island with a limited number of bridges and tunnels.

However, consider what you could do in phase 2, which is robotic buses. Imagine that people's incoming robotic cars gather in parking lots on paths to the bridge, and 50 people get out and get quickly into a robotic bus. The bus takes them over the bridge to another lot, where 50 single person robocars await. They quickly get into those and are taken along Manhattan's wide avenues and streets to their destinations, and then the cars come back for more.

Now let's put the buses back to regular car headway or 2,000 vehicles per hour. Here just the 3 lanes of the Brooklyn bridge (in one direction) are enough to bring 300,000 people per hour into Manhattan -- again on just the Brooklyn Bridge. Add the Manhattan bridge and you have enough for almost 700,000 people per hour. Buses are transit you might say, but these are unlike transit as you know it. You would only ride them for a few minutes to get around the bridge bottleneck, and there would be no waiting either to get the bus or for your robocar when you got off it. (You might wait for a slot on a bus, but you would wait at home, your own robocar not leaving until it is scheduled to meet a bus on which you have a reserved slot, and the other 49 people's cars doing the same.)

Now this is extreme. We would not do it this way for many reasons. First of all there are lots of bridges and tunnels and lots of capacity, especially with reversed lanes. And we do still have those subways so we would keep using them, though we would use them in concert with robocars (which might get entrances to drive down to the platform level) and they would make far fewer stops to be express. Because the buses would be simply cycling back and forth over the bridge, you would not need an endless supply. With a 15 minute round trip, 3 lanes of buses would require 1,500 buses, which seems like a lot but there are probably that many subway cars. If the buses were standup rather than sit-down they could hold even more, and could do even better if they were articulated multi-car buses, which would not be a problem for a gig like this.

No, the robocar capacity, in its full form in the all-robocar world, is immense, and dwarfs any transit system. How could it not, when there are so many miles of road, and transit rails are no different from road in capacity once you can fully control them. That's some time away, but so is the withering of transit.

### Virtual Bus

Wouldn't the various RoboCars simply assemble into a Virtual Bus? I.e. minimal spacing, lead vehicle controls speed and direction, following vehicles just react to speed changes in the vehicle ahead. Higher density and better fuel efficiency from drafting. Not quite as dense perhaps but more efficient for latency (i.e. users time) as long as the overall capacity of the road network is adequate.

### Pretty close

And in any city that didn't have a very limited number of streets going to the CBD you would not need to use this temporary switch to real buses.

It's just a square footage thing. A person in a robocar needs about 50 square feet plus their headway space (whatever that is) while a bus with 50 people needs 400 square feet plus the bus headway space.

How much headway? People debate that. Ordinary cars try for about 1.8 seconds at highway speed. Robocars can of course do better and eventually can draft. However, my own safety algorithms call for never occupying more than 50% of the road space, so that there is always room for vehicles to swerve into gaps if the need comes.

### Can you please post Amtrak numbers?

Hi Brad, I recently rediscovered this site after a related discussion on high-speed rail at work. This site is simply the best analysis of mass transit efficiency I've ever seen. You noted in a comment that you don't list Amtrak because it is not considered a form of transit, but I think it would be very useful to show these numbers considering current debates around high-speed rail in the US. Would you mind adding Amtrak to your post charts or (at least) including the BTU per passenger mile number in a reply to my comment? Thanks!

Btw, the 2011 Insight EPA combined MPG appears to be 40/43 and Consumer Reports (CR) got 29/45 in real road tests (38 combined). Am I correct in thinking that the Prius is currently the best transit competitor in the US? CR reported 32/55 in real road tests (44 combined), EPA says 51/48. My experience is that CR numbers are more accurate.

### Amtrak

Is 2398 btus/passenger-mile in the 2008 DoE data book. There are links to the data book in the article above. That's about 50 passenger-miles/gallon of gasoline -- they use higher energy diesel so it will be a bit higher than that per gallon of diesel.

HSR figures though could vary greatly from this.

• HSR will probably be electric. Electric efficiency varies greatly from grid to grid, but it tends to be somewhat higher than diesel.
• It really all depends on load factor. Amtrak has pretty good load factor, I have to presume, because it does not run frequently and does not have to run frequently (unlike transit.)
• High speed trains are less efficient than slower trains due to high aerodynamic drag, but tend to have better aerodynamic shapes, and may be longer to make up for it. Energy lost do drag goes up with the square of velocity, so a 180 mph train has 9 times the energy need per mile over the same train at 60mph. Aircraft make up for this by flying high where air is thin.

### The real green is LESS MILES

So air travel looks not so bad by this chart... well, that's because per-passenger it isn't so much worse than driving the whole way. But it's the distance that is the real problem. The problem with private cars isn't the inherent efficiency, it's the idea that private cars let people live in spread out sprawl and drive everywhere. If people live near transit, then they go less total miles and use less land in sprawling McMansions. It's definitely less efficient to have a bus or train go through winding subdivisions versus cars! The real answer is not to build these ridiculous subdivisions. But anyway, there are also issues of infrastructure and quality of life, because a traffic jam is a lot worse than sitting in a crowded moving train, and roads need more repair over years than rail, not to mention have more dangerous accidents and cause more stress...

### The "real" answer

While it is true that reducing travel, or not building sprawl would reduce energy use. But when you talk about the "real" answer the big question is, can you get people to do it? The extent to which people will be greener for the sake of being green is not zero but it is fairly limited, especially if it costs them time, convenience or money or other things they truly value, particularly having safe environments with places for their kids to play.

The real answer has to be both greener, and desired by the public. You can pass laws but even the power of that is limited.

### Eonomic Analysis, Not BTU or Carbon Counting

Brad,

You've done a very good job here. You have obviously made an honest appraisal that was motivated solely by a desire to inform. I do admit that I am flummoxed to learn you were surprised by these findings. If, as you contend, you have been analyzing these issues for decades, I wonder why it comes as a surprise? It doesn't to me although I am woefully late to the party.

Nevertheless, the real critique I offer concerns the singular, almost myopic focus with analysis using BTU or CO2 as the coin of the realm rather than total life-cycle economic costing. Utterly absent in your analysis is the impact of capital costs, and thus total life-cycle costs, from competing solutions. Fine, if we need to impute a cost for CO2 emission, let's do so. But let's assure ourselves it reflects actual costs in a rationally-functioning global marketplace, not some politically-inspired artificial cost imposed by corrupt, rent-seeking boosters of alternative energy. And if capital costs are unrealistically low at a given moment, as they are in 2012 — the yield on the 10-year Treasury is below 1.5% — then let's agree to use a longer-term average.

But none of these recommendations is worth a moment's notice if we're just counting carbon or BTUs to make our choices. You can't take those to the bank. People can't exchange them for groceries. They can't buy an iPhone with them. You can't purchase a tanker of Venezuelan crude oil with them, etc. Long-range economic planning, including energy policy, obligates us to look at net present value dollars where energy serves merely as one input. Sure, we need to properly assess the costs of all impacting externalities like pollution, climate and so forth. Unfortunately, when discussing this topic, the largest pollution problems we face are polluted public policy analysis due to economic myopia compounded by junk science-driven environmental advocacy.

I hope in future, some measure of rational economic analysis can find its way into our carbon and BTU counting. Then we might start making some sensible public policy choices, because our energy and transportation infrastructure public policy choices will be competing, side by side, with other public policy initiatives like health care, education, food safety, security and a thousand other concerns.

Joseph Toomey
Author, "Change You Can REALLY Believe In: The Obama Legacy of Broken Promises and Failed Policies"

### Why energy?

First of all energy is one of the things we get an accounting on, and it's a good overall proxy for a big part of operating cost. Yes, capital costs are important but also highly tied up in legacy issues -- a train my have a private ROW that was laid down in 1890 that could never be duplicated today. The capital is both long paid for and priceless. It is good to know what the subsidy is for all the various modes and ROWs. Transit is almost all subsidized (though usually based on operating costs) and roads are of course almost all taxpayer funded with a few toll exceptions, with gasoline tax doing some compensation.

Energy allows a workable side by side comparison on overall efficiency and that's a good thing to look at.

### Still green to take public transport

"That's because the transit is running anyway, so the incremental cost of carrying one more passenger is indeed less than just about any private vehicle. It is similarly green to carpool in somebody else's car that's going your way.

As such, these numbers should not make you feel better about taking your car instead of the train. Particularly solo, since solo drivers are what make the car's average efficiency worse while carpoolers make it better."

True, but it makes me feel a lot better about voting AGAINST new public transport projects. San Jose examples include BART extensions and the "fast" train to LA. Not that I had trouble voting against them before. The Bart extension to San Jose was put on the ballot several times and the money "redirected" to other projects each time. Seen the Bart extension to San Jose lately?

### Number for passenger ferries?

Hi Brad, I referenced your essay in a FB discussion about public transit, and a question came up about passenger ferries over water, specifically the Vallejo to SF ferry. Do you have any numbers for water passenger transport? Where would they fall on your graph?

### wrong road

Sigh. I accept your numbers and the conclusions you draw from them. But do you really think the solution is new cars? New, expensive cars that most of us will never be able to afford to buy? The solution is not new stuff. Any new stuff. The solution is to stop manufacturing stuff, ESPECIALLY cars. For one thing cars are the worst thing we've ever invented,; all they've done is allow us to live an insane distance from where we conduct all of our other activities and to fill the intervening space with asphalt to drive and park our cars on. This is insane. Okay, the infrastructure exists, we're gonna need cars for awhile while we transition to a more walkable infrastructure (although of course this won't happen; we'll swallow the planet whole before we make significant cultural changes) but we have all the cars we'll ever need and then some. What happens to cars when we're done with them in the first world? They're sent to the third world, where they are reconditioned and used for another couple of decades. We don't need any more cars. Ever. Nor do we need more mass transit. We need to re-think our whole way of living from the ground up. Of course I'm enough of a realist to know this will not happen, but I also know that building new cars won't really change much. Our culture is structurally incapable of stopping it's destructiveness or even slowing it down, and barring a miracle or catastrophe we're probably just plain screwed.

### Many wrong assumptions

The solution probably is personal transportation. But not expensive -- actually cheaper than existing cars and existing transit, and using less energy.

You might call for us all to stop making stuff, but that's an ideology, not something that will actually happen. You have to give people what they want. You can't tell them what to want, not very effectively. Order them to want it and they'll find ways around you, or at least the rich will. The good news is that greener is more efficient and more efficient is cheaper and people already want that.

Do you have figures on how many cars make it out of developed world recycling into the hands of the poor? Cars have a lifetime in miles. You can maintain them past that lifetime, but it becomes more expensive to maintain them than they are worth.

### Is Green U.S. Transit a whopping myth?

Wonderful discussion on some of the energy realities behind various transportation types. Thanks for all the work you put into this.
I have done some of my own studies on this subject matter and must generally agree with your conclusions. What became obvious to me was that cars are far more efficient than most other powered transport methods if ride-sharing is used. Adding some trip consolidation and planning will make the car becomes a top contender.
Jet aircraft are also moving into much higher efficiency ranges with new highly efficient ducted fan engines and upcoming fuselage designs, planes will use 50% less fuel. That really puts a crimp into the ultra-expensive high speed rail that is often touted by many.
Thanks again for compiling and analyzing this very important and relevant topic.

### Thank you for the research and clear presentation

Brad, thank you for the excellent post. It was presented in simplicity and kept objective and based on good data so far as I can tell.

I'm surprised by the difficulty many commenters have to appreciate the effort you have made to keep this post accurate and unbiased, and respond to any comments that find you at fault for any reason. Any such post or essay should be approached with skepticism, but many of these commenters are just directly negative. I think you have made the point quite clear that you are not attempting to bash or promote any particular form of transportation. Only to present data as you revealed them in your research.

One question that I have that I didn't see addressed (hopefully I didn't miss somewhere), did you in any way account for energy losses due to accidents, damaged and totaled automobiles, and energy to sustain medical practices required due to accidents. I am sure this is incredibly difficult to quantify, but as I imagine medical equipment is probably very energy intensive to produce, maintain, and operate, it may be a significant consideration regarding the total energy impact of automobile use.

Of course accidents with mass transit also occur, but I believe the death and injury toll associated is far less per travelled mile.

Thank you.

### Accident cost

I have never heard of this being quantified. To make a typical car consumes the energy of 1,000 gallons of gasoline, but a 30mpg car will consume about 6,000 to 7,000 gallons in its life, so the number that are retired early is real but probably doesn't make a big change in the numbers. I doubt the energy costs of the accident industry (medical etc.) factor a lot either. But I have not done the math.

### The missing/overlooked cost of high density urban transit

Brad,

I appreciate your posts on this topic; and even more so your honesty in your attempt to come to some "true" totals regarding the efficiencies of public/mass transit systems.

I'm especially appreciative of the fact that you include the point regarding population density as being one of the KEY factors of the "efficiency" of systems like the NYC subway; and that absent such densities, such a system simply ISN'T implementable elsewhere.

BUT... one point though that is STILL missing from the "high density urban public transport system" -- and to my mind (once you see it) it is a glaringly OBVIOUS one -- is that unlike private cars elsewhere, it really ISN'T a true "door to door" cost. What is so glaringly missing? Elevators.

That's right, elevators.

Plain and simple people (and every "analysis" I have ever seen) simply IGNORES this aspect (and it's costs, both to build, maintain and operate) as if it were NOT a part of the equation (or had zero cost/energy).

But of course it IS part of the equation, and it DOES have costs & energy expenditure. The urban world is NOT 2-dimensional, it's 3-dimensional -- and transit systems (expending energy) MUST exist to enable/facilitate that 3rd dimension.

Moreover, no system like the NYC subway could be anywhere NEAR as "efficient" as it is without the high-density population -- both in terms of residential point of origin, as well as final destination -- WITHOUT those elevators, people simply would NOT (could not) live in a 20+ story building and/or work in a 40+ story office tower... there is simply no way that they would walk up/down (much less carry goods) THAT many flights of stairs. (IOW absent elevators, people would {and did/do} live AND work in shorter buildings, which then means lower density).

So the person who lives on say the 10th floor of building A and who works across town (or indeed even right next door) on the 23rd floor of building B, tends to simply take for granted that there is ENERGY being expended (and a major capital investment as well as maintenance costs) to both lower and raise their body those 10 & 23 floors... in both directions, and at each end. So the claim that they simply "walk" between buildings, or that they take the "efficient" subway... is to simply & wholly ignore/dismiss the fact that the walking/transit is NOT truly "door to door"; thus the claim is a false one, it is "incomplete" in terms of energy & systems.

By contrast, people who live in (generally single or stair-access double or at most triple story) suburban homes or apartment buildings, and then commute via private vehicle to some similar ground-level (or again at most "walk-up") work location... well THEIR "transit" IS in fact invariably the full total "door to door" cost. That is to say, there is no additional "machinery" (and fuel or electrical energy) used to convey them from their home to their car, or from the car to the office/factory/store.

What that means, is that when urban systems are compared against suburban systems... the comparison is fundamentally DISHONEST.

Moreover the costs of those elevators (capital construction a well as maintenance & operation) are far from trivial. (See this article -- http://www.facilitiesnet.com/elevators/article/Economics-of-Elevators-Facilities-Management-Elevators-Feature--1539 -- for some idea of that). And of course those systems are often VERY inefficient: they serve only a relatively small number of people, are generally empty (or nearly empty) for fully half of their operations (and moreover expend nearly the same energy to move when empty as they do when full {it isn't merely the weight of the elevator car, but also the counterweight}).

I'd also like to note one other (different) thing -- yet it is also something that is falsely allocated -- and that is (especially in regards to exurban or rural people) the "cost of building maintaining the roads". This is frequently cited as some "subsidy" to those living in the rural/exurban areas. What that ignores of course is that those roads exist PRIMARILY for other purposes: take Agriculture as one main example, the roads give machinery ready access to farm fields, and we're not talking about just the tractors and/or harvesters, but also the trucks that haul the produce... that is to say carry the food. Where? Well primarily INTO the cities.

Likewise with the freeway system -- it wasn't built for and doesn't exist SOLELY (or even primarily) for suburban commuter traffic -- rather it is chiefly used to via trucks to transport GOODS from one city to another (as well as from various rural or exurban or suburban {NIMBY} processing plants and factories and distribution centers).

The whole point being that the extremely "high density" urban environments CANNOT exist without that entire "network" of roads and vehicles to support it. Neither NYC (nor any other major metropolis) is even capable of producing more than a trivial fraction of it's own food, much less the raw materials or finished goods.

And any analysis that tries to separate the "countryside" and make it seem like it should operate in a similar fashion to the "high density city" -- but which DOESN'T take that into account...

Well, let's be honest; such an analysis is "disconnected" from reality, and in a very childishly ignorant or oblivious fashion. It's akin to (literally) the child that thinks food just "magically" appears in the refrigerator on an as needed basis; or that mommy/daddy obtain "money" (from an apparently endless/infinite supply) by just punching numbers into some ATM machine, or merely handing over some "piece of paper" to the bank teller; and then said child wondering WHY people need to "work" or go to "jobs".

The urbanite (and that includes many clueless academics an bureaucrats -- especially those raised in "privileged" home) is often essentially JUST as clueless about (or worse being disingenuous and willfully ignoring) what all happens out in "flyover" land; or worse who think that all those people "out there" should "ride public transport" instead of driving trucks around (I mean TRUCKS, really?)

Anyway... just some food for thought.

### Energy use

I have not seen the energy bills for a large elevator system, but perhaps you can find them. I don't think it's as high as you say. I presume there is regenerative braking, so the energy generated by elevators going down is put into elevators going up. The counterweight is a good thing -- it's what makes that system efficient. In the end all mass lifted up comes back down again, and some fraction of its energy is recoverable, though I don't know how well these systems recover it. But lifting things up is actually one of the most effective means of energy storage we have; it's what we do with reservoirs, pumping water up into them at night to capture the energy when it comes back down.

### Impact of transit use on passenger miles

I have seen these numbers on US transit energy inefficiency in a number of places, and I think that they are widely misunderstood. The first thing is that, as you allude to, that energy efficiency of transit is strongly correlated with ridership. The US has favored auto-centric transportation and land use planning for decades which has resulted in low population densities and high levels of automobile use, which makes transit operations less viable. However, since public transit is federally mandated, most US transit systems operate with lower utilization rates (persons to seats) and this results in low energy efficiency.

However, as transit supportive transportation and land use policies get implemented, ridership tends to increase and this generally results in much higher energy efficiency. You do touch on this in your article.

One important thing that should be mentioned however, is that transit ridership has a significant impact on passenger miles. People who use transit tend to use walking and biking for a significant percentage of their trips. This means that if two people living in the same neighborhood who also commute to the same business district, with one of them traveling by car and the other transit; the person who drives will tend to make all of their trips by the car and significantly more miles than the transit rider. For example, the transit rider will tend to make non-commute trips by foot or bicycle either within the business district or in their own neighborhood, while the driver make go all over town to make the same sort of trips.

The holy grail of energy efficiency in transportation is walking and biking. High quality transit (especially grade-separated rail) is key to impacting land use and creating walkable, mixed-use neighborhoods; and therefore, this kind of public transit tends to have the biggest overall positive impact on transportation energy use.

### Updates

This article is quite old, you will want to look at much more recent visions of transit in the future. Walking and biking actually become much easier when you have one way robocar taxi service, as you can now mix and match modes as you like. However, the robocar transit gets really efficient, even more efficient than you are likely to get with traditional transit based on big vehicles, fixed routes and fixed schedules.