All posts by David Levinson

Phantom Trips

Adam Millard-Ball has a nice article on Phantom Trips. in Access Magazine

Traffic lies at the heart of many fears about new urban development. In some cases, cities require developers to scale back housing or retail proposals to alleviate concerns about congestion. In other cases, cities widen roadways, add turn lanes, or lengthen signal cycles to accommodate projected traffic volumes.

In both instances, planners and engineers wield considerable influence through their predictions of the number of vehicle trips that a proposed development will generate. This seemingly mundane process—trip generation analysis—profoundly shapes the physical form and financial feasibility of urban development. Estimates of trip generation help shape the road infrastructure, determine the amount that developers must pay for new roads and greenhouse gas mitigation, and sway local support or opposition to proposed development. Trip generation practices also help determine how much urban space cities dedicate to cars; the viability and character of transit-oriented and infill development; and whether a project proceeds at all.

How do we predict how much more traffic there will be? In the United States, the Institute for Transportation Engineers’ (ITE) Trip Generation Manual, now in its 9th edition, is the standard reference. It provides data on the number of trips generated by 172 different land uses, from “Baby Superstore” to “Cemetery.” Some of the land-use categories are remarkably specific, such as “Batting Cage” or even “Coffee/Donut Shop with Drive-Through Window and No Indoor Seating.”


Given the ubiquitous influence of the Trip Generation Manual on the built environment, it is important to understand the validity of its data and ITE’s recommended practices. Rather than accurately forecasting the impacts of new developments, I show in this article that ITE substantially overestimates trip generation rates. Moreover, I explain why ITE’s core premise, that development always generates new trips, is misleading in many circumstances. Because ITE rates do not fully consider how trips are reshuffled among destinations, they are often inappropriate for evaluating traffic, fiscal, and environmental impacts. In short, we are planning for “phantom trips” that never appear in reality.

This article is adapted from “Phantom Trips: Overestimating the Traffic Impacts of New Development,” originally published in the Journal of Transport and Land Use. [forthcoming 8(1)]

Adam Millard-Ball

adam millard ball

Assistant Professor in the Department of Environmental Studies at the University of California, Santa Cruz (

Accessibility moves out of the lab and into practice

Eric Sundquist at SSTI writes: “Accessibility moves out of the lab and into practice

Accessibility, long considered a more robust measure of transportation system success than simple mobility, is moving out of research and into practice, according to panelists on an SSTI webinar.

Accessibility measures the ease by which travelers can reach desired destinations, or “opportunities.” Often, but not always, it is measured in terms of time. As such, it combines both mobility and proximity of land uses, bringing together two directly connected public policy concerns that are often poorly integrated in decision-making.

While accessibility is not a new concept, data limitations have made it difficult to measure. Now it is becoming practice-ready, panelists said.

The webinar, broadcast Dec. 4, featured Andrew Owen of the University of Minnesota’s Accessibility Observatory, Richard Kuzmyak of Renaissance Planning Group, and Kate Sylvester of the Maryland DOT. Slides and a recording are available on the SSTI website.

Owen, who cited commentary in the conservative National Review and libertarian Reason Foundation about the benefit of accessibility measures, has been working with Minnesota DOT and now is developing a pooled fund study to mainstream accessibility measures across the country. Kuzmyak has applied accessibility measures in the Washington, D.C., area, including in a project with Sylvester’s Maryland DOT.

While both efforts aim to make use of accessibility for better transportation and land use decision-making, the approaches are somewhat different.

Owen’s group uses a cumulative opportunities count, generally using jobs as the critical opportunities. They estimate the number of opportunities that can be accessed by car and transit from neighborhoods around the nation within a set time, say 30 minutes. …


Autonomy Island

Ricardo Montalban and Herve Villechaize Fantasy Island (1977)
Ricardo Montalban and Herve Villechaize Fantasy Island (1977)

“Ze Car, Ze Car.”

“My dear guests, I am Mr. Roarke, your host. Welcome to Autonomy Island.”

Yes, here on Autonomy Island, all of the cars are autonomous. Your adventure will be to ride and drive in a place without fear of a human running you over.

When will an automaker (or collective of automakers, or government, or Google) buy all the cars on an island (and perhaps rent the government), replace them with new autonomous vehicles, and see what happens … to safety, to travel behavior, etc?

This is the kind of real world laboratory experiment that would be highly useful to understand the implications, the unintended side effects, the bugs and so on of robotic cars.

For instance, take the US Virgin Islands. St. Croix has a population of about 50,000 people. If it follows general US patterns, it has about 33,000 light vehicles. For about $1B [Less than the cost of a single NFL stadium] all of the cars could be replaced with autonomous vehicles at about $33,000 each. [This might be a stretch, but that would be a typical mass production cost.]

The USVI collectively has between 10 and 20 auto fatalities annually. At a $9.1 million value of life, that is at least $91M per year. In 11 years, the experiment would pay for itself if in fact it eliminates fatal crashes the way autonomous vehicles are expected to, leave aside any other potential benefits.

The advantages of an island are that it is a closed system, it can be fully mapped, no one can drive on or off. The advantages of a real island with real people are the ability to see how these interactions might actually occur in use.

Autonomous vehicles interacting with only autonomous vehicles should be much easier to design than autonomous vehicles in mixed traffic, as the environment is less variable. People, animals, weather, and so on are still potential confounding factors, but should be simpler to manage than a person in a car.

Accessibility and the Allocation of Time: Changes in Travel Behavior 1990-2010

Congratulations to Martin Brosnan for successfully completing his MS Thesis: Accessibility and the Allocation of Time: Changes in Travel Behavior 1990-2010. He is now a consultant with CDM Smith in Illinois.

Martin Brosnan
Martin Brosnan

Using detailed travel surveys conducted by the Metropolitan Council of the Minneapolis/Saint Paul region for 1990, 2000-2001, and 2010-2011, this study analyses journey-to- work times, activity allocation and accessibility. The analysis shows a decline in the time people spend outside of their homes as well as the time people spend in travel over the past decade. Although distances per trip are increasing, the willingness to make trips is declining, resulting in fewer kilometers traveled and less time allocated to travel. This study finds accessibility to be a significant factor in commute durations. Accessibility and commute duration have large effects on the amount of time spent at work therefore activity patterns are influenced by transportation and the urban environment.

Accessibility and the choice of network investments in the London Underground

Congratulations to David Giacomin for completing his MS Thesis: Accessibility and the choice of network investments in the London Underground. He is now a consultant for Kimley-Horn in Nevada.

David Giacomin
David Giacomin


In 1863, the Metropolitan Railway of what came to be known as the London Underground successfully opened as the world’s first subway. Its high ridership spawned interest in additional links. Entrepreneurs secured funding and then proposed new lines to Parliament for approval, though only a portion were actually approved. While putative rail barons may have conducted some economic analysis, the final decision lay with Parliament, which did not have available modern transportation economic or geographic analysis tools. How good were the decisions that Parliament made in approving Underground Lines? This paper explores the role accessibility played on the decision to approve or reject proposed early London Tube Schemes.

That’s Transportainment

Transportation and entertainment are ever inter-twined.

Every movie is a road trip*, and not just the obvious ones, like Thelma and Louise or National Lampoon’s Vacation, or Apollo 13. The linear narrative of  movies is constrained to follow the single dimension of time, marching ever forward. While attempts at braking the strict linearity are possible (think about flashbacks, or Rashomon like stories, or Pulp Fiction) within those cul-de-sacs it remains a road trip.

Many stories star or feature transportation. Not just the obvious ones like the Faster and Furiouser series, or Gravity, but any story which involves motion and gadgets. In some cases they attain human-level personality. I have a long series of posts documenting the use of Anthropomorphic vehicles: automobiles, planes, helicopters, trains (1) (2), lorries, omnibuses, monorails, construction vehicles, and boats.

Outside of movies, sporting events too are about motion. Running of course is simply who can move the fastest (unaided, unhindered). Hurdles is who can move the fastest, with hindrances. American Football is about who can move a ball across about 90 meters of territory with a limited number of stops, ensuring at least steady progress.

NASCAR is even more obvious. A sport that emerged out of the use of cars during prohibition to avoid the law. Going around a racetrack in a vehicle 400 times is interesting enough to attract more than 145,000 people to attend an event at the Charlotte Motor Speedway and 7 million people to watch on TV. [Though apparently in-person attendance is dropping]. While we might complain about dozens of vehicles traversing 600 miles and doing no physical work (i.e. returning where they started), the more severe environmental consequences of the race are not due to the racers, but the fans, traveling hundreds of miles themselves.

Having now been to Charlotte, the Charlotte Motor Speedway, and the NASCAR Hall of Fame, I have first hand knowledge of the magnitude of racing in the local culture. You too can drive a car on a race track for a not inconsiderable piece of coin. You learn that people have purchased condominiums overlooking the race-track. You learn they are now “right-sizing”. You learn the stands are multi-colored so they look more full in ads even when they are not.

Charlotte Motor Speedway from the Infield
Charlotte Motor Speedway from the Infield

Not only is entertainment about transportation. Transportation has become about entertainment.

I am not talking just about the in-vehicle entertainment systems designed to entertain you while you travel, thereby making travel less onerous (and more frequent).

Many, if not most, of today’s transportation network investment decisions are made by people who won’t regularly use the thing they are deciding on.  In one sense, this must be true, there are many facilities, and only so much time in the day for decision-makers to travel, given our relative centralization of decision-making in the hands of government.

It is not only the specific links and segments of networks, but entire modes that go mis-understood. We have evidence this is true. Decision makers may try to imagine how they will use the facility, but cannot develop a full scenario where their home and workplace and other activities moving, which would enable them to see the package as a regular user. They are limited to envisioning their occasional interaction with the link or mode. In this sense, they are viewing the facility the way a tourist might, rather than an everyday user.

Fort Worth Pedal Pub
Fort Worth Pedal Pub

We posit the decision-makers (or anyone’s) view of the transportation modes, links, and vehicles that they don’t use is much as yours is at the amusement park or a place where you are a tourist: a ride, part of an urban entertainment package, an appendage to a game or concert or night-on-the-town wrapped up as an event.

These rides-cum-transportation are designed to lure people who have nothing better to do with their time than be entertained. If these projects were self-financing, more power to them [perhaps raising emotions of disdain for those who have nothing better to do with their time but spend it on a ride and trivial amusements, but not particularly impacting anyone else].

Unfortunately, these investments  are not self-financing, except in the fantasies of economic development analysts and perhaps in the special case of Pedal-Pubs [I don’t actually know the financial arrangement of Pedal-Pubs, but I assume, given their proliferation, they are profitable].

It’s heeding the cry of the child “I’m bored, Entertain me”.

The Georgetown Gondola
The Georgetown Gondola

It is fantastic that decision-makers believe our society has so much wealth and so many resources that there are no more important problems to solve, that we can build urban amusement park rides for the sake of the novelty-seeking joy-riders. That we can prioritize circuses over bread. That we can rise up the social Maslow Hierarchy of Needs from security and basic mobility to societal self-actualization and social entertainments. That we can fuse entertainment and transportation into a newly converged transportainment (hopefully obviating the need for entertainment on the subject).

Do they really believe that?

Certainly, most travel is not “work” travel [most people don’t have regular jobs], but much of it is productive (or re-productive). And if everyone had the opportunity to  simultaneously have adequate housing and adequate transportation, then public subsidy for transportation as entertainment (or housing as entertainment – which in the US is generally left to the private sector) would not be the worst way to spend our social surplus.

Yet I keep hearing that there is insufficient affordable housing, and more than a few people walk or ride bikes not out of choice but for lack of affordable faster modes, and many people ride on buses that take 2 to 3 to 4 to 5 times as long as cars for the same trip (not even considering schedule delays) because they cannot afford or otherwise cannot drive a car, AND because the transit system is so poorly designed it takes so long to get to many places.

Every 1.7 billion dollars spent as part of the urban transport-tainment system is 1.7 billion dollars that cannot be spent on more serious and economically productive urban needs of travelers without the luxury of time and choice, improving their safety and reducing their travel times, or just giving them the resources to make choices.


* A comment first noted by my wife, a lit-crit major in college.

Transportainment River is the appropriate name of a company that builds waterpark rides.

Midway Airport |

This post is part of Snark Week at

The St. Paul Ports Authority, in concert with Metro Transit, has decided to replicate Chicago’s successful example and build a new airport at Midway. Just as Minneapolis-St. Paul International Airport is on the Blue Line, the new St. Paul Airport at Midway [Airport Code; SPAM] will be conveniently located at the junction of the Green Line and the A-Line, and at the interchange of I-94 and Snelling Avenue. Officials say the existing Midway shopping centers can remain, since their parking lots are already empty enough to land a plane on.

Spruce Tree Center, Saint Paul Minnesota Painting by Carolyn Swiszcz, 2001
Spruce Tree Center, Saint Paul Minnesota Painting by Carolyn Swiszcz, 2001


“This is the kind of transit-oriented development that will put street level vitality back into the Midway District” said Foppus Loppet, head of the Midway TOD Planning and Implementation Task Force Alliance (MT PITFall).

Metro Transit expects that the airport, with convenient crosswalks across University Avenue, will add 973 riders per day, depending on the number of flights. It is expected that I-94 will be used as an approach flight way, with flights landing from the West and taking off from the East on the one runway.

The terminal will be an adaptive reuse of Spruce Tree Center, with a jetway across Snelling Avenue to connect to planes on the apron just east of Snelling Avenue.

If this airport is successful, it is expected Transit-Oriented Airport Development (TOADs) will be implemented along all Twin Cities Transitways, making air travel as convenient in the Metro as it is in Chicagoland.

Approval is pending a decision by the Federal Aviation Administration.

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