Evolution vs. Plans

Evolution

Assuming we started with an undeveloped wilderness,  cities emerge at selected points (typically points with natural accessibility advantages over their neighbors, such as ports and harbors, or water falls, or railroad junctions). But they evolve from wilderness to city over time.

They do not generally evolve because someone built city-scale transportation out in the country and waited for the people to arrive.

Instead it is a ratchet: a few people, some transportation network investment; some more people, more investment; even more people, still more investment, and so on, until something resembling a city emerged.

While the infrastructure may slightly lead the development (as in the Streetcar Suburbs or London’s Underground) those developments in general contiguously extended the urban environment in appropriate steps, and were accompanied by development in the near term (failure to see development would have led to bankruptcy for the line).

Plans

Plans aim to take this chaotic, unpredictable, evolutionary process and put a sheen of order upon it.

The general problem with public sector transportation and land use plans is that they are static. They are made for one point in time. They are  snapshots in a world with 24 frames per second (for eternity), and for which we don’t know the ending (“no spoilers”).

Life-cycle of rail in the US. From The Transportation Experience, Figure 6-4
Life-cycle of rail in the US. From The Transportation Experience, Figure 6-4

 

They design for maturity and implicitly assume that the mature (built out) city sustains. The evidence from the life-cycle for every mode (or technology) is that its scope and extent are continuously changing.

The mirror of this problem is  they ignore the path that gets you there and all interim states, as well as changes in behavior and technology that may occur in the interim.

The third problem with plans is that they address future problems that don’t exist today, when there are plenty of problems today that remain unsolved. Trying to better manage how will people get around or from or to a site which might (or might not) transform from country to city, or even low density suburb to high density suburb, in 30 years when there are plenty of ways to help people get around better today is an exercise in pointlessness, whose primary objective is to transfer resources from the public to selected (and one presumes politically influential) landholders.

There is nothing wrong with having a vision. It presents a direction in which to proceed. The most important thing is the next step (or two) though. Each step you take in one direction is a step farther away from destinations in other directions. But the path on which we are walking is shrouded in smog. Our vision is simply our imagination (or consensual hallucination) of what lies down the road. We have never been there before. But we must recognize, we never will reach where we think we are going.

On “Induced Demand”

 

JW Writes:

I strongly agree with David King’s recent post that we so often forget accumulated knowledge and that we seem to re-discover this knowledge in endless cycles. Nowhere does this seem more true than in the field of economics, which brings me to the reason I reacted so strongly to David’s post.

I hate the term “Induced Demand”. I hate the idea that induced demand is something bad; something to be avoided.

In economics 101 we learn that demand is a function – not an amount. It is presented to us as a two-dimensional function. To make the math easy, it is then reduced to a one dimensional (linear) function so we can calculate elasticity and solve problems. In fact, demand is a three dimensional function, with time parameters, and is not a zero dimensionless point.

We only arrive at an amount (of travel) when we intersect the supply function with the demand function. Transportation improvements, whether the construction of a new runway at an airport or the signal coordination along an urban arterial, change the supply function, and therefore the amount of travel consumed, and the price.

When we consume travel, we are actually consuming something else. It is instructive to think in terms of David Levinson’s formulation of “access” instead of travel. Access is a Merit Good. Merit goods are what most people think of when they talk about Public Goods, without the messiness of concerning ourselves with rivalry and excludability. Merit goods are normally associated with positive externalities; and as such are considered to be something that individuals or societies should have on the basis of need; and something that will be under-supplied by the market, making public provision desirable.

From the individual’s point of view, access provides opportunities to more jobs, more entertainment and social options, and more alternatives for consumption of goods and services. From a business’ point of view, access provides a larger pool of labor and more raw materials. From a retailer’s point of view, access provides a larger pool of consumers. From a municipal government’s point of view, access allows more efficient provision of police protection, fire protection and ambulance service by reducing the number of facilities necessary for a given response time.

Transportation improvements that provide greater access per unit of time lower transaction costs. Lower transaction cost lead to great efficiency in the economy and a higher standard of living.

In telecommunications networks we have witnessed several orders of magnitude improvement in capacity during our lifetimes, yet we have always filled the new capacity. We stream video now when we used send text files. Yet no one wrings their hands about the induced demand in our telecommunications network.

The Many Flavors of Transit

Public policy for mass transit in the United States is largely focused on a few modes of travel: commuter rail, urban rail, urban bus, and paratransit requirements. These few modes certainly carry most of the transit riders in the country, but do not represent a full understanding of the breadth of options that are required to make a truly transit-oriented city. New York is the most transit-oriented city in North America, and it is likely that when most people not from New York think about transit in New York they think about the subway system, or perhaps they include iconic yellow cabs or remember that there are a lot of buses. If you ask most New Yorkers, they will probably add many other modes, but even then there will likely be many modes left out.

An underappreciated reason why New York functions so well as a transit-oriented city—and can grow transit ridership without new expansion of core services (yet)—is that there are oodles of transit options available. Mode choices for travelers is not a binary choice between driving and transit, even though this has been the general attitude toward transit policy over the past few decades. Observing travel in New York suggests just how complex the required systems are to actually provide meaningful alternatives to automobility.

Below are 33 different categories of mass transit offering regular service in New York City (I have reviewed this list with native New Yorkers but I am sure others will have constructive comments about my categories). This is what it takes to create transit-orientation for a city, and I suspect many of these exist in cities everywhere but planners and scholars are not aware of them. In New York lots and lots of operators offer many different services to many different types of people. Not all technologies work for all places, so transit technologies should reflect the problems to be solved.

  1. MTA subways
  2. PATH subways
  3. MTA buses
  4. New Jersey Transit buses
  5. Metro-North Rail Road
  6. Long Island Rail Road
  7. New Jersey Transit trains
  8. Staten Island Ferry
  9. Staten Island Rail Road
  10. Water taxis
  11. Commuter ferries (Five licensed operators)
  12. Access-a-Ride (MTA and other transit provider contracts)
  13. Yellow taxicabs (Medallion cabs)
  14. Green taxicabs (Boro cabs)
  15. Liveries for Hire (Uber, Lyft, Carmel, etc.)
  16. Executive Limousines
  17. Liveries (informal)
  18. Commuter vans (licensed and pre-arranged fares; e.g. Mario’s Transportation)
  19. Dollar vans and local jitneys (informal immigrant services)
  20. Chinatown buses (intercity)
  21. Low cost intercity buses (Bolt Bus, Mega Bus)
  22. Conventional intercity buses (Greyhound, Peter Pan)
  23. Apartment shuttles (CoSo, etc.)
  24. Company/corporate shuttles
  25. University shuttles (Columbia University, New York University)
  26. New Jersey commuter jitneys
  27. Long Island commuter jitneys
  28. Roosevelt Island Tram (Gondola)
  29. Roosevelt Island Red Bus (Publicly owned development corporation)
  30. CitiBike bike share (public access for a fee)
  31. University bike share programs (free access for a designated group)
  32. Amtrak
  33. Executive helicopters

When planning local transportation systems we now commonly say that multiple modes are required. We underestimate how many modes this is and how challenging it is to accommodate everything. Each of these 33 categories represents different customers, fare policies, public/private ownership, terminal capacity, vehicles, road access, curbside access, infrastructure needs, etc. Most of these different types of transit are regulated under municipal or state laws, too, and require the allocation of public space (roads and waterways) more than large-scale capital investment. I outlined some of these challenges in a recent CityLab piece.

The main takeaway from this is that for transit to be useful it must reflect the many ways people need to get around the city. Multi-modal transport doesn’t mean cars-transit-bikes-pedestrians. There are multiple modes of transit, too.

City vs. Country

One of the many dysfunctions in transportation and land use planning is our collective inability to recognize the difference between city and country.

It’s really not that hard. In the country  distances between buildings are large, while in the city they are short. In land use jargon, densities are lower in the country than the city.

City Mouse and Country Mouse
City Mouse and Country Mouse

The most useful form of transportation varies between city and country.

In the country, individual, point-to-point, on-demand service (foot, horse, bike, car) saves a great deal of time over feasible shared, scheduled, fixed-route services (transit). That time savings offsets the individual cost savings from sharing a vehicle with other passengers.

In the city, shared transit services are on the whole less expensive to the user and society than individual services. The small increase in time is offset by cost savings from sharing. The greater density allows more frequent service and more direct service nearer the traveler’s trip end points.

Idealizations

In idealized low-density places like Wright’s Broadacre “City”, local transportation was clearly individuated, to the point it appears everyone has a private gyrocopter.

Howard's Garden City (1902)
Howard’s Garden City (1902)

In Howard’s Garden “City”, individual transportation was used to get around town, and to the inter-municipal railway.

In Jacobs’s New York City and Toronto, walking was used to access transit for longer distance urban and inter-urban travel, while the car was not especially welcome.

From both a transportation and land use perspective, each of these works on its own terms (assuming gyrocopters actually work).

Greenwich Village, New York (wikipedia)
Greenwich Village, New York (wikipedia)
Wright's Broadacre City (1934)
Wright’s Broadacre City (1932)

Stable points

Green Routemaster Bus serving suburban and exurban London
Green Routemaster “Country Bus” the kind that used to serve suburban and exurban London

 

Routemaster Bus (from wikipedia)
Red Routemaster “City Bus” (from wikipedia)

In short, in the current technological environment, there are two stable points: one where a sufficient number of people have abandoned their personal cars and use transit daily that transit is sustainable with high frequency and ubiquity; and one where people keep their cars and use transit on special occasions (to go downtown or the State Fair for entertainment, e.g.).

Once the car is owned, the marginal cost of the additional trip to most destinations (since free parking is found for something like 99% of all destinations in the US, gas prices and taxes are low, and we don’t have road pricing) is sufficiently low it outweighs the combination of low costs of shared transit vehicles with higher travel times.

A metropolitan area is large enough to contain multitudes. There can be a center where people can live car-less because the transit (or walking or biking) is good enough for daily city-based work and non-work trips, and a countrified-edge where people can live transit-less, since living and working in the suburbs is seldom a market transit can well serve (except as an accidental spillover where people are lucky or skilled enough to have home and work aligned on the same radial transit line).

 

Forgetting Faster Than We Learn

There are many players in the world of transport policy these days. On net, this influx of new actors into the policy, advocacy and planning realms is likely a benefit, but does offer some concerns. One thing that I see again and again is that new entrants and existing players in the world of urban transport policy too often don’t know or have forgotten lessons learned in the past. On one level this is just a nuisance, and it is good that old knowledge is rediscovered. On another more troubling level this is like health professionals having to rediscover penicillin every other generation.

Here are two recent examples where existing knowledge is ignored or not known or marginalized.

In a recent Vox piece the concept of induced demand was discussed with reference to recent empirical work by the economists Gilles Duranton and Matthew Turner (a few months ago Wired also wrote about this particular work.). Induced demand is a well-known concept that goes back at least to Anthony Downs’ “Iron Law of Congestion,” yet the Vox piece suggests induced demand is new knowledge. Reading beyond recent urban economics research reveals that scholars in transportation economics and urban planning have extensively explored induced demand. Here is a 1995 article by Mark Hansen in ACCESS where he describes the problem. Robert Cervero, Robert Noland, Robert Cervero and Mark Hansen and the Transportationist himself (note to regular readers: this post is by David King, not David Levinson) are some of the scholars who have published in leading journals, presented at conferences and included induced demand in their teaching. Here is what Robert Cervero wrote in 2000:

“No issue has paralyzed highway programmes and side-tracked our ability to rationalize new road development as concerns over “induced travel demand”. Time and again, experiences show that building new roads or widening existing ones, especially in fast growing areas, provides only ephemeral relief – in short time, they are once again filled to capacity. A study using 18 years of data from 14 California metropolitan areas found every 10 percent increase in highway lane-miles was associated with a 9 percent increase in vehicle-miles-traveled four years after road expansion, controlling for other factors. Similar findings have been recorded in the United Kingdom. In the United States, regional transportation plans, such as in the San Francisco Bay Area, have been legally contested by environmental interest groups on the very grounds that they failed to account for the induced travel demand effects of road investments and expansions.”

This ACCESS article (2003) by Cervero is worth reading for nuance about what induced demand really means for transport planning and policy. He notes that while induced demand claims have stopped highway expansions in the past, induced demand claims gloss over more important concerns about the use and costs of travel.

It is also worth noting that even though induced demand is usually discussed in the context of expanded road capacity induced demand actually applies for any particular transportation technology. Transit expansion along a corridor has the same effect on induced demand as road widening. On his blog Kevin Krizek explained how congestion is a poor argument for expanded cycling facilities also because of induced demand. We actually know a lot about how transport capacity affects the price of travel, which affects demand for travel across time and space.

A second example about forgotten knowledge has to do with taxi policy. In a recent opinion piece about how wonderful Uber is Mohamed El-Erian describes how Uber will disrupt the inefficient taxi stands near Penn Station in Midtown Manhattan:

“Arriving earlier this week in New York at Penn Station, I joined many others in a rather slow-moving line for taxis. I did so out of habit. But a few minutes into my wait, I realized that the smart thing to do was to pull up the Uber app on my phone. In a few seconds, Uber linked me up with a car, which picked me up four minutes later. The driver was courteous, and the vehicle was clean. And all this for a fare that was similar to what I would have paid for a traditional cab — after a much longer wait, that is.”

This is a terrible argument for Uber type services and reflects little understanding about how taxi networks actually work on existing streets. The whole reason we have taxi stands is because it is really inefficient to have hundreds of people emerge from Penn Station (or any event, station, airport, etc.) to hail hundreds of cabs. We do not have the street capacity or curb capacity to accommodate this, and some type of queuing is necessary. The Uber model, as described, only works when a few people are using the service and is simply not scalable to the extent that a taxi queue is.

These are just two examples, but lots of people are wading into transport policy based on limited reading and personal anecdotes, and if we follow their lead we will have to relearn all the things that we already know. Forgetting knowledge is not a new phenomenon and not limited to any particular set of experts, but it is problematic and deserves more discussion about how to fix it. In a recent lead editorial in the May 2014 Planning Magazine (gated link) the American Planning Association’s CEO, Paul Farmer, begins as follows:

“During a chat about planning in the U.S. and Canada, several planning colleagues addressed the topic of value capture. “We’ve coined the phrase ‘windfalls,’” one Canadian colleague proudly remarked in describing the unearthed benefits that a property owner might realize from investment made by others. The late Don Hagman might have been pleased, amused, or irritated by this appropriation of the concept he popularized, if not invented, in his extensive writings half a century ago.”

(The book referenced is Windfalls for Wipeouts: Land Value Capture and Compensation.)

Concern about keeping knowledge alive isn’t just sour grapes about all the stuff I learned in grad school that people ignore. It’s not clear how we can steadily move policy forward (in a better way, however “better” is defined) if we can’t keep the lessons of the past in mind. This is not a question only for transport policy, either. In a recent book Jo Guldi and David Armitage argue that historical study should play a larger role in economic and policy debates.

As transport policy attracts more specialists from fields outside of transport—economics, computer science, software engineers, data miners, etc.—the challenge of sharing existing knowledge rather than rediscovering knowledge is really important. We don’t need to have lots of policies that won’t work just to relearn than such policies don’t work.

Park and ride lot geometry

I don’t find park and ride lots attractive. I don’t want them in my neighborhood. I wish the land around park and ride lots were valuable. But let’s do some math.

In one acre, there are 43,560 square feet. It takes about 300 square feet to store a parked car (including lanes, etc.). This suggests you can store 145 parked cars per acre. That is similar to this result.

If every one of those parked cars carried 1 person, that is 145 transit boardings from that station in the morning (and 145 boardings elsewhere in the evening, assuming symmetry). That generates 290 daily transit trips.

In contrast, let’s say we had zero park and ride spaces. Let’s further assume that adjacent land uses have a 50% transit mode share for work trips and 0% for non-work trips. We would need 300 resident workers on that acre to have a similar number of transit trips generated. Since only half the population works, we are looking at 600 total persons on that acre of land. That is the equivalent of 384,000 persons per square mile. That is a lot of people.

Even if only workers lived there, and they had 100% transit mode share for work trips and another 2 non-work trips per day by transit, that is still 145 people per acre. That is the equivalent of 92,800 people per square mile. That is Manhattan like densities (actually higher). Of course not all of Manhattan is high-rise apartments, so that is not necessarily as high as the highest densities in Manhattan, but it is higher than the lowest densities in Manhattan.

Low, or even medium, density land use around the station will not enable as many transit users  as the park and ride lot.

I still don’t like park and ride lots.

Jarrett Walker has a different take

A One-Track Mind

While at this point, we are almost assuredly beating a dead horse, until the Green Line Extension (Southwest LRT) is actually under construction, there remains the possibility it can be improved. While the best improvement (given the existence of an LRT to fourth ring Southwest suburbs) would be to route it along a path where people actually live, if we cannot maximize benefits, surely we should minimize costs.
I speak of course of the tunnel under the park.

Kenilworth Sections
Kenilworth Sections

The stated reason is the right-of-way is insufficiently wide to accommodate two tracks of LRT, one track of freight rail serving about 3 trains a day, a bike path, and the buildings that were built where it would have been convenient to run some more track.
There are two obvious solutions to this problem which have not been given serious consideration as far as I can tell.

First, the freight and LRT can share the track at different times. The experience with Northstar certain demonstrates why having a few passenger trains on a freight railroad can create lots of passenger delay, but this is different, it would be a freight train on a passenger track owned by the public.

Everyone says “But, FRA”. I realize there are institutional barriers which need to be overcome. Perhaps those are more expensive to overcome than $130 million, or whatever the difference in the surface solution and what the tunnel will cost.

Second, if one-track is good enough for freight, why is it not good enough for LRT for a short section? (This is an idea previously considered by Matt Steele at streets.mn.) This of course is a tight fit, and may require waivers from appropriate regulatory authorities, but is physically possible from the drawing I have seen.

Section B-B
Section B-B

For the sake of argument, let’s assume we want to single track 1.5 miles, with trains going up 45 miles per hour (say an average speed of 30 mph to make the math easy). This would take 3 minutes. The trains are on 10 minute headways in each direction, or one train every 5 minutes through the bottleneck. (Note, Matt assumed 2 minutes, and higher speeds. I am using conservative assumptions).

If timing were perfect, there could be zero delay from this scenario. This is a deterministic case. That is the assumption underlying Matt’s post.

However, as we know, timing is rarely perfect, so we need to look at stochastic delay. Stochastic is engineering jargon for random. Random is engineering jargon for a case where multiple outcomes have an equal likelihood of being chosen (or some are more likely than others, but we cannot be sure that would be the case).

Even when things are random, that doesn’t mean we cannot ascertain the average of the distribution.

Let’s suppose we  have an arrival rate of 1 train every 5 minutes (our arrival rate lambda=0.2 trains per minute), and a server rate of 1 train every 3 minutes (mu=0.33 trains per minute). If the systems is completely random (and we certainly hope it is better than that), we can use stochastic queueing theory to estimate the delay.

Worst case (aside from someone actively and maliciously controlling the trains so they do arrive at the same time (which implies that deterministic solutions with zero delay are possible)), we can model this as an M/M/1  queue (meaning, as wikipedia says: arrivals follow a Poisson process and job service times have an exponential distribution) . This assumes Markovian (random) arrival and departure processes and a single channel.

The utilization rate (rho = lambda/mu) is 0.6, meaning the server is busy 60% of the time.

Math gives us a formula for the average queue size:

Average queue size = rho/(1 – rho) = 1.5

Math gives us a formula for the average wait time :

E(w) = lambda / mu*(mu-lambda) = 0.2/(0.333*(0.333-0.2))=4.5 minutes

At 1 million passengers per month (12 million per year) for 30 years, this is 360 million people delayed 4.5 minutes=1.6 billion minutes of delay. At $20/hour, this is $533 million.

Clearly this value is larger than the cost of the tunnel.

On the other hand, perhaps we only need to single track for 0.5 miles.

In that case, the server time is 1 minute, so mu=1. Capacity utilization is 20% (i.e. rho is 0.2). Average queue size is 0.25 trains. The average wait time is 0.25 minutes.

Our 360 million people are delayed 0.25 minutes at $20/hour is $30 million. This is considerably less than the cost of the tunnel.

The train speeds could be adjusted so no-one would know they were delayed (i.e. trains would slow down approaching the switch, or be held at the previous station, as needed. And remember this is worst case, delay should be less than this with any competent schedule adherence. With perfect schedule adherence, they are indeed zero (our deterministic solution).

Single-tracking is a solution to high capital costs. It is not optimal, it has delay costs  that depend on the length of the stretch, headways, how much control Metro Transit has over running times, and so on.

Everything involves trade-offs.

There is of course a concern about running LRT next to (near) freight trains, carrying lots of explosive ethanol. I say, don’t do it. Run them at different times, even if on different tracks. If freight trains are only permitted at night, or in a mid-day window when an LRT is held upstream of the pinch-point for a few minutes, or ideally in a scheduled break, there should be zero chance of collision. There is always a chance of derailment – that doesn’t change, but derailment is less hazardous than collision for what I hope are obvious reasons.

In the long run, maybe freight will go away (e.g. once people stop using ethanol), go somewhere else, or another solution will be found. At that time, the line can be double-tracked if needed.

In the short term, the money saved could be used to temporarily relocate the trail to quiet residential streets nearby, compensate the neighborhood, give money to the Park Board, or any number other socially worthwhile goals.

Crossposted at streets.mn.

a blog about Networks and Places

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