All posts by David Levinson

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.

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).

 

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.

Accessibility Webinar

Andrew Owen of the University of Minnesota Accessibility Observatory will be talking about accessibility October 28 at FHWA’s:

Tuesday, October 28, 2014 1:30:00 PM CDT – 3:00:00 PM CDT
The Federal Highway Administration, in cooperation with several national stakeholder groups, would like you to join us for the next Let’s Talk Performance: Performance Measures Beyond the Mainstream.   The webinar is scheduled for Tuesday, October 28, from 2:30PM to 4:00 PM (EDT).  This event is open to FHWA staff, State DOTs, MPOs, transit providers, and other stakeholder agencies.  This webinar is the second in a series of six webinars focused on transportation performance management implementation activities.  During this webinar, presenters will:
•	Provide an update on FHWA Rulemaking proceedings; 
•	Focus on States and MPOs evaluating non-traditional performance measures 
 Register Now 

During the webinar, the following presentations on non-traditional performance measures will be made:
• Accessibility Performance Measures
o Andrew Owen, University of Minnesota Accessibility Observatory
• Economic Development Performance Measures
o Charlie Howard, Puget Sound Regional Council
• Health Performance Measures for Transportation Agencies
o Frank Gallivan, ICF International

The 60-Year Line

Whenever we build a piece of large-scale infrastructure, we should be thinking about the markets it serves today, and the market it serves over its lifetime. We are often building lines that aim to promote development. That is, they are serving non-places in the hope they become places. The evidence on this is mixed. Sometimes lines successfully promote development, sometimes they don’t. If the lines were privately built (as in times of yore), this would be much less of public policy question, as the public is not bearing the monetary risk. That is not to say there are no policy questions, the line-builder wants right-of-way, and that often requires eminent domain powers.

However the lines are now publicly built, so the public is bearing the risk so that the privately owned lands might appreciate in value, and the public might get a small share of that increment. Usually we don’t employ value capture. General tax revenues are not nearly enough to justify the line, since lines are expensive now — all the good lines, the low-hanging fruit, have been built, and most development is a transfer from one place to another.

The risk is the capital outlay will not be recovered from future revenue (from users, or non-users).

In contrast, building lines where people actually are, where demand currently exists, presents much lower risk in revenue projections.

Lines typically last upwards of 60 years with a given technology. We certainly cannot predict 60 years into the future. 60 years ago was before both the Shinkansen and the Interstate Highway System. Predictions from 60 years ago about today were not terribly accurate. Sixty years is longer than a Kondratieff Cycle.

Will today’s places have any activity in 60 years? A good test of that is whether the place had activity 60 years ago. Look at the map of 60 years ago. Where was the activity? Where is it today? The intersection of those two maps show places with proven longevity. There are no guarantees those places will have activity in 60 years of course (“past performance is no guarantee of future results”), but they are more likely to because there is an underlying cause for the stability of the place. That is, there was a cause for that place to develop in the first place (e.g. a useful waterfall, a port, or a junction between intercity rail lines), and the positive feedback structure between transportation, accessibility, and land use actively worked to reinforce the strength of that place.

Value Capture Flowchart
Value Capture Flowchart

Applying that to the Twin Cities, the best prediction you can make is that there will be strong demand between Downtown Minneapolis and Downtown St. Paul. We currently serve that corridor with interstate highway and transit.

Applying that again to the Twin Cities, the newest places (if we can call them that) outside the beltway are making claims for long-term investments of resources fixing them into the urban system without the evidence of long-term stability (See e.g. the SW LRT to a park and ride lot on Mitchell Road, or Highway 212, or the Bottineau Line to a cornfield, or Highway 610). It is certainly possible those destinations will become significant demand generators, but it is far from certain. If a private firm wanted to bear the risk of those prospective developments not working out, more power to them. But the public is asked to do this, while perfectly good markets go unserved or underserved for lack of capital.