Be suspicious of Travel Demand Models

When it comes to transit forecasting, you should always be suspicious of anything coming out of a travel demand model. The Traffic Analysis Zones (TAZ) are often too large, and the travel times on the centroid connectors often reflect car access from parking lot, rather than walk-access from the curb, which, given the exponential decay in walking trips due to distances, leads them to over-estimate ridership for malls and strip-commercial.

Hamish Cambell Gets it

"This is why transit agencies obsess over frequency and easy connections. The difference between trains every 3 minutes versus every 9 minutes is not three times worse. It is exponentially worse. At 3-minute frequency, a missed connection costs 3 minutes. At 9-minute frequency, that missed connection compounds into schedule disruption, late arrivals, and cascading delays through your day. Add capacity problems where you might not fit on the next train, and the costs compound again. You are not just waiting 9 minutes. You are waiting 9 minutes, then maybe another 9, while also managing stress about being late and uncertainty about whether you will even make it on. Research consistently shows riders will choose a slower direct route over a faster route requiring transfers. They are not being irrational. They are avoiding compounding costs that planners can measure but riders simply experience as too much friction."

Hamish Campbell "Why Distance Compounds Costs in Cities"; Cities + Transport 2026 February 2

Key point is the anxiety acts as a travel time multiplier. "If I miss this one, how long do I have to wait for the next one?" Riding the bus already includes anxiety of boarding. Add a transfer doubles that. Reliability overcomes the anxiety. If you can't afford frequency, then you've got to manage reliability. Clockface scheduling is great, but--if you promise a bus every 15 minutes, but can't deliver, that's worse than not promising anything. 

Bus reliability and Planning TIme

If you ask people what they want from public transport, they usually say "Speed." But if you look at behavioral data, speed isn't the most important factor. Reliability is. I would rather take a bus that takes 40 minutes guaranteed, than a car that takes 20 minutes but might take 60 if there is traffic. Uncertainty is stressful. Knowing "I will arrive at 8:55 AM" is worth more than "I might arrive at 8:30 AM". This is why dedicated lanes (BRT/Tram) are so powerful. They might not be fast, but they are predictable. We don't need to break the sound barrier. We just need to keep a promise. Do you prefer a fast gamble or a slow guarantee? - Juan Mora Triana

When my bus was scheduled to arrive at 7:55, I had to catch the bus scheduled to arrive at 7:40, because the second bus was late in picking me up. I worked in an office, being 5m late wasn't critical--but it earned me an unfriendly glance from my boss. And so, I started taking the earlier bus. And so, what was nominally a 23m trip (7m walk, 13m bus ride, 3m walk) started to eat 40 minutes out of my day. 

Making it worse was the irregularity in what was nominally a 15m bus. The 7:40 bus would be on-time, or early. The 7:55 bus would be 7-10 minutes late, reliably. So reliably that I began to time my walk from my house to the bus stop to start when the 7:55 bus was supposed to arrive, knowing that the bus wouldn't have arrived before I reached the bus stop. But that was for a bus I took five days a week. 

When I was trying to take a new bus to someplace new, I'd stroll up to the stop, pull its schedule out of my pack of pamphlets, use the system map to check which routes it serviced, pull out the appropriate schedule for the route, and check my watch. Then I'd take half the headway and estimate the blocks, figuring I could make 8 SLC blocks (~1 mile) in 20m, and that the bus moved about 3x that fast. For a 15m bus, I'd estimate a 10m wait (half the headway plus some uncertainty). For a 30m bus, I'd estimate I'd be waiting 20 minutes--the actual wait time plus what I could have walked waiting for the bus. For the hourly bus--I'd start walking. The combination of wait time plus uncertainty plus lost walking time made it a bad bet--my standard estimate was that I was better off walking two miles than waiting for an hourly bus. 

Even today, any trip under 10m, I walk. It's less stressful, because it's less uncertain. Even with a bus with a 15m headway, odds are I'll make it a half mile before the bus comes. I've repeatedly had the frustrating experience of seeing the bus I would have liked to take pass me by... but not often. 

Rapid transit, it's the same calculation, except that I remove the mental 'penalty' for potential to be late. The station will be nicer, there will be places to sit, there is an arrival time count-down [2] and I know the vehicle will be on time. Riding TRAX in SLC, if the train was 15m late, I'd tell me wife "Someone is probably dead" [1]. 

This also tied into my willingness to make transfers. My rules of thumb were that it was always worth it to transfer between a 15m bus and rapid transit, sometimes worthwhile to transfer between two 15m buses, and worthwhile to take a 30m bus TO rapid transit (but not the reverse). Anything else, I was better off walking. So I did a lot of things like taking TRAX west then south and then walking east from a Trax station, because it was a better bet than just waiting for a 30m bus to take me directly south. The bus would either be delayed in arriving or delayed enroute, where TRAX was practically a guarantee.

Admittedly, I was young and fit, with plenty of time to kill, and Salt Lake is a very safe city. But I also didn't have any other options: No car and lack of plowed sidewalks/lanes made biking in winter in SLC prohibitive. 

[1] After enough highly reported crashes at railroad gates, people quit racing the train, but someone racing the train at a red light stills seems like an annual event. SUV drivers are used to being the biggest thing on the road, but in a car-eat-car world, a train is an apex predator.

[2] Transit Information systems that only provide scheduled GTFS arrival times, rather than real-time GTFS data about vehicle location are a cruel joke, so knowable false that they can only be considered a deliberate deception.

The slippery slope of federal funding

There is a motorism-based ideology in transportation planning that says that the public sector should never pay for internal circulation. Like most of the tenants of motorism, it's based on early interstate highway development, and the ideology of what the Feds were and were not going to pay for. 

The Federal government was going to pay for the limited access highways, and the state governments were going to pay for anything local. But, given the generosity of Federal funding for interstate construction, the definition of 'local' shortly ceased to include on-ramps and off-ramps, or viaducts onto the freeway, or access ramps to the viaducts, or anything that could be reasonable be justified as being part of an Interstate so the feds paid for its construction/paving.

But interstates come with interstate design standards, which include high speeds, which require large curve radii, which conflicts badly with urban street grids, necessitating a lot of demolition. And once you've got someone willing to pay for demolition, it's very tempting to direct that energy to someplace you've been wanting to do slum clearance anyway. 

Kansas City Streetcar, fixed guideway transit, and marginal pricing.

Wikipedia tells me that the OKC streetcar, post-pandemic, was costing $420k a year, collecting $60k a year in fares, for a net loss of $360k a year. With perhaps 15k riders, that's about $23 dollar per rider, which is absurd. So, I hope the areas it is serving are experiencing a whole lot of additional economic activity and new development, because that's a lot. 

More absurd is that a few years earlier, it was free to ride but had 75,000 riders. So the math says $420k a year, collecting $0k a year in fares, for a net loss of $420k a year, for a cost of about $6 per rider. So running things fare-free, they were getting 4x the benefit! 

The case for 'free buses' is often questionable--is the reduced travel time reduced stop times worth the reduced fare? But for fixed guideway transit, the calculation is different, because a fixed guideway transit system already represents millions in fixed costs investment. The OKC streetcar was built on the cheap, for $23m. So assuming a (SWAG) of 4.35%, they are already paying a million dollars a year of interest on the debt to build the thing. So its not $420k to operate, it's 1,420k to operate. Which, at 15k riders, is ~$94 a rider. BUT! At 75k riders, that's ~$19/rider. 

Once you've built a thing, your best option is to maximize the service you are providing. And the way to do that is to make the marginal cost of people using the service as close to zero as possible. And the way to do that is a pass system. My yoga studio runs $150 a month or $30 a class. And when I'm on a per-class basis, it makes me reluctant to take a class. But while I'm on the monthly pass, I've got every incentive to maximize my use. And that's exactly the logic every fixed guideway transit system should be exploiting, because their marginal cost of additional trip is very small, and their fixed costs very large. 

Of course, during the commute peak, transit capacity actually matters and its standing room only. But that's a fraction of the day, and the rest of the day should have discount pricing. Restaurants don't have 'happy hours' because they want you to be happy--but to draw people in during a slack time where they have to 'staff up' prior to the peak, and so they suffer the costs regardless. 

National vs. Federal

A couple of books suggest that it's nonsensical to speak of an American "Nation":

• Albion's Seed
• The Nine Nations of North America
• American Nations

Hence the use of the term "National" as a synonym for "Federal" strikes me as awkward. In an originalist sense, the "United States of America" reflected a political claim of a military alliance, a sort of echo of the "Union of Utrecht" and later "United Provinces", but the actual governmental structure of the United states is a federation, "a group of states with a central government but independence in internal affairs". 

To speak of a nation is to speak of a collective national identity based on shared language, history, ethnicity, territory and society. It is certainly possible to speak of an 'American Nation', but to speak of a "National Transportation Plan Goals" seems awry -- the authoritative entity providing the planning goals is not a nation. But for many places, 'nation' has a kinder tone to it, because it implies a sense of collective identity, but also of shared burden: everyone labors under the same requirements. 

San Jose Affordabilty Gap

The supply of land is limited. If you keep all your increasingly valuable land to existing structures, the price of those structures goes insane. Keeping homes affordable means reducing the amount of land per home. San Jose gasped and clutched its pearls, Prop 13 protected homeowners from economic incentives to sell, and now the whole state's housing market is a disaster area. If you want house prices to get sane again, you'll have to build enough rental units that the price-premium for housing makes renting the preferred option, and only those aspiring to build equity through homeownership actually buy houses.

There is a movement afoot to blame income inequality for this, and it undeniably plays a role--when you use price to ration the supply of something (like houses), the people with the most money buy them. And when you artificially constrain your house value assessment via madness like Prop 13, they have zero incentive to ever sell them--a couple of days of AirBnB annually to pay the taxes.

Transportation regime shift

Transportation-wise, road/rail isn't either/or but rather an "and/also". Past a certain point, a central place can no longer boost/sustain its accessibility with cars alone and has to add rail. But that shift doesn't happen everywhere at once, and when you've got a regional governance structure, it takes a long time before it reaches a supporting political plurality. At first, the shift in the transportation regime only affects the most central areas, but over time it ripples outward.

Parking at the periphery

"But where will people park?"  Public garage/lot at end of street--so there should be minimal automobile pass through traffic, and what does pass through will be slowed by geometric design - curb bump-outs all over.

Every bit of walkable urbanism follows the same pattern - parking at the periphery. High Street in Morgantown WV, Shepherdstown WV, Sugarhouse UT, 25 Street Ogden UT, Silver Spring, MD, Pike and Rose in Bethesda, MD, Cary NC. If you want an intact street wall people like to walk along, you've got to put the main parking someplace else--behind the buildings, at the end of the street, in a garage. (Parking tucked under buildings is the preserve of CBD-adjacent areas with high-rise offices).

We've known since Appleyard (pere) that wide streets and heavy traffic limit people's ability to cross the street reflects the friction of crossing is such that the far side of the street is functionally further away. So if you want agglomeration economies of having the things across the street be close, street design needs to reflect it. Any landlord or developer that aspires to have a destination location rather than convenience-oriented strip-retail needs to understand this. Anyone who aspires to TOD needs to understand this. Mall developers understand this.

Because enclosed malls are so auto-dependent, it's easy to miss that they are the original 'pedestrian pocket' of walkable urbanism. Despite the higher cost of enclosure (and heating/cooling all the space), they have become the prime retail location, and no small part of that is because they satisfy the demand for walkable urbanism. Agglomeration economies certainly play a role, but the form matters. Flipping an enclosed mall (stores around a sea of parking) destroys the agglomeration economy--no one is going to walk from one side of the ring, through the parking lot, to visit something on the far side. Even the enclosed mall's 'junior' form -- the lifestyle center--a walkable pedestrian-oriented center strip with stores on both sides, with a parking garage on one end.

Always the same pattern--pedestrian pocket wrapped in retail, with the automobile (largely) exiled to the periphery.

Origin density at transit stations

Origins tend to be rather more spread out, and it requires pretty high density to generate more riders than a Park-and-Ride, which generates one rider per 400 SF. A three-story apartment is actually worse than a Park-and-Ride--not everyone in those apartments will take transit, and parking + landscaping will take up over two thirds of the parcel.  A 2-3 acre bus depot will likewise collect more riders than a garden apartment. So making a fuss about the density of origins near a transit station is rarely worthwhile across most of America. 

Further, origins highly concentrated on a small fraction of land parcels, and highly concentrated on buildings located within those parcels. As getting places requires getting to the front door, it's that access that matters for transit supportive density, while most origin destination calculations are made using metrics like units per acre. Pure geographic coverage is a terrible metric for access--most of the land is empty or occupied by things like private yards. 

Transit supportive density is a bit of a red herring

"Transit supportive density" is a bit of a red herring. The Utah Transit Authority build a very successful transit system by destinations where parking was expensive to build (downtown, universities & colleges, hospitals) and using a mix of PnR and transit centers to aggregate origins. So for making transit work, what really matters is destination density--how much stuff is within a walkable distance (10m) of the transit station? 

TOD > Missing Middle

Using public transit to fix car-dependence is a failing strategy. Providing marginal transportation to marginalized groups (teenagers, people with disabilities, older seniors) is at best a band-aid and at worst a sop. Further, no level of public transit provision will ever be able to fully replace automobility. Hence, undoing car dependence is largely a land-use problem: allowing the magic of density and mixed use to shorten trip distances and enable non-auto modes. Since most of the magic in transportation shifts happens at a pretty high threshold, it's key to focus on land uses in a small portion of critical places. From a transportation perspective, enabling good TOD at a few places beats enabling Missing Middle everywhere.

Not to say that the Missing Middle doesn't matter. Most of America is caught on the threshold where the densest multifamily that's financially viable is the 3-story 'garden' apartment with a huge parking lot, such that until land prices rise to a level where 'wrap' apartments with structured parking become viable, almost no new apartments get built--rather, more and more 3-story apartments get built, just at increasingly peripheral locations. 

TOD without transit

Of course, for places without fixed guideway transit, it's easy to claim that TOD doesn't matter. That misses the point. Read Calthorpe, and you quickly understand that TOD is just his early "Pedestrian Pocket" wrapped around a transit station, with all the same elements: higher density, a mix of uses, and a walkable street network. Counter-intutitively, there is no need for a transit station for these elements of TOD-ness. 

The 'bones' of a walkable street network and the regulatory context of permitting a mix of uses and higher density are simple to establish. But to actually get density, and to get the commercial uses supported by a local population, is much harder. Sandy Civic Center Trax in Utah tried for decades before achieving even minimal transit supportive density and barely supports minimal retail by the station even now. 

Hence, TOD: a way to increase the footfall traffic at a location, so commercial amenities at the station can draw not only from the local population, but the commuter population. It's not by accident that Calthorpe drew TOD as one-sided--he was omitting the massive commuter parking lot across the arterial road from the picture.

Picture any civic center, downtown, and urban district you've ever visited, and you'll see the same elements: a density of activity, a mix of uses, and a walkable street network. And on the periphery, some large parking lots and a major arterial. Self-contained autarky is impossible; local density alone cannot supply the dollars to support the commercial services or supply the staff for the commercial retail/services--any center must draw on people from outside the center and must facilitated people traveling to do so. 

But the key element to having and sustaining a pedestrian pocket is prioritizing internal circulation is prioritized over regional access. And that, rather than transit access, is the core of TOD. A transit station wrapped in parking lots isn't TOD. A transit station with a multi-level bus transit center isn't TOD. Because in both cases, the area near the station is designed to facilitate regional access. It's not by accident that transit agencies are bad at TOD--it's contrary to their institutional mission of providing regional transportation. 

The purpose of TOD is to use a transit station to facilitate the existence of a pedestrian pocket, and the elements that represent TOD have very little to do with transit stations. Rather, they are the principles of facilitating pedestrian-scale urbanism, and those principles can be applied without the need for a transit station. 

Motor Socialism

 We have oriented our infrastructure investment to guarantee the provision of roadway and parking capacity in amounts necessity to eliminate scarcity. "Motor socialism" if you will. And our society has become structured around that investment schema, such that a lot of people are sustained by the status quo. A rupture with that is going to be bad for a lot of people, and they are going to fight hard to continue and preserve it.

Facilitating traffic - attraction or circulation

Picture any civic center, downtown, and urban district you've ever visited, and you'll see the same elements: a density of activity, a mix of uses, and a walkable street network. And on the periphery, some large parking lots and a major arterial. Self-contained autarky is impossible; local density alone cannot supply the dollars to support the commercial services or supply the staff for the commercial retail/services--any center must draw on people from outside the center and must facilitated people traveling to do so. But any center must also facilitate circulation within itself*, and it is that tension between attraction and facilitation that makes urban traffic such a muddle**. 

That tension can be resolved in favor of either, but results in very different outcomes. If attraction is subsidized, you get a very good network of higher speed roads between pods of development. If circulation is subsidized, you get a very high-quality pedestrian realm, comfortable local traffic, but very poor access for traveling long distances. Neither resolution is reliably superior to the other, but rather which should be preferred is context dependent.

 

*Also what makes freeway interchanges so hostile to urbanism and incapable of being 'centers': an interchange of an expressway with an arterial generates four islands of highly accessible land, equal in dignity, but prohibits circulation between them. 

** Grade separation resolves the urban traffic muddle but is expensive to implement. The contrived solution is grade separation--witness endless Chamber of Commerce plans for skybridges and pedways, and highway megaprojects like Boston's Big Dig, or Los Angeles triple-track rail trench. It's not a new solution--practically as soon as railroads emerged, demands for grade separation followed, generating elevated and subway lines. 

Suburbia Requires a New Transportation Technology

We built the first suburbs based on passenger trains, the next set based on grade-separated urban rail, and a third set based on streetcars. Then we did it again with the automobile, and again with the limited access highway. In every case, it was a new transportation technology making previously inaccessible land more accessible and making it accessible in such volume that an urban development pattern built on cheaper-then-previous-urban land happened. Each time, over time, the flood of new resource was exploited, but further exploiting it required greater and greater investment, leading to declining returns, until things petered out, and the financial of the new development pattern no longer worked. 

No one recognizes this today, because for three generations we had a massive subsidy regime where we taxed gasoline to pay for new limited access highway miles. That subsidy regime went bust in 2008, and the last fifteen years have been a scramble to prop it up. Because there is a lot of money invested in suburbia continuing. There are entire industries predicated on turning raw land into suburban houses, and entire polities dependent on that process, and there is an awareness if that engine stops running, our entire economy might tank. (Japan's did. China's is). 

So the smart money gets that another round of suburbia requires a new transportation technology. So there is a lot of investment in both flying cars and connected and autonomous vehicles*. Both are oversold, because the people developing both are trying to recruit enough investment money to actually develop a saleable product, so they overstate the benefits their product will provide. The most basic way they do that is talking about how much time drivers will save, which sounds great to drivers. But to anyone involved in infrastructure (planners, transportation economists, engineers), everyone is very clear that driver time is not the limiting factor in our transportation system but rather road capacity, and driver-time has heretofore been a limitation on driver utilization of road capacity. So even if every vehicle becomes a CAV, traffic will not disappear, and indeed, will likely grow worse.

I say new technology because old technologies aren't going to save us. We are already familiar with their characteristics, with their limitations, and make use of them where appropriate and efficient. But having another round of suburbanization relies on a transportation technology sufficient to make a massive volume of previously inaccessible land available for development. 

My personal bet is on flying cars, simply because they don't have right-of-way costs. But flying cars have the same issues as automobiles, if not worse: they take up a lot of space. So they may be useful at the periphery, they don't solve the problem of making trips between two regimes: the low-D autocentric regime, and the high-D geometry-hates-cars regime. 

Urbanization and Transportation

The spatial arrangement of urbanization is determined by trade in whatever is valuable. If that thing is rare or dense, you build cities at natural crossroads. If it's bulky, you get cities near navigable rivers. If it relies on combining things, you build around ports. If you rely on bulk inputs, your build at the fall line. 

Urban Regimes

It's critical to recognize that for travel behavior there exist different urban regimes, which can be defined in terms of the "D variables" (Density, Diversity, Design). And in one regime, it's painfully absurd to do anything but drive. Distances are long, routes are indirect, all the infrastructure is auto-centric, parking is plentiful and free. And that regime characterizes 95% of the urban area. But when distances are shorter, routes are direct, you've got infrastructure that is safe and humane for people not in cars, and parking is painful. Useful transit exists. And in the latter regime, that car is no longer the most efficient mode of transport.

And when that happens, we should stop privileging the automobile as the most efficient mode. Even conceptualizing what it would be like to privilege another mode is astonishingly powerful, because it rapidly leads to a catalogue of things we have to do for cars: the space we provide, the risks we tolerate, the funding we provide, the denial of access, the regulation of unrelated matters (Daylight Savings Time), the distortion to every development, etc. And we have to ask: "If cars are no longer the most efficient mode, why are we spending millions prioritizing the movement of cars, and mandating everyone else spend millions providing for the storage of cars"?

The simple answer is that for most trips, one end of a trip lies in the auto-centric regime, and it's a choice between imposing costs in the smaller area where cars are less efficient, or in the larger area, where cars are more efficient. And benefitting the suburbs to the detriment of central cities was official US policy for decades. It wasn't until the "Urban Transportation Problem" hit, when congestion outstripped road building, that thoughtful people realized building their way out of congestion was impossible--traffic was growing faster than the capacity to pay for it, even as the cost of paying for it became exponentially higher. And then we started building rapid transit. (And saving older transit systems). 

Geometry hates cars

The simple fact is that geometry hates cars. Cars are an amazing way to travel, and for most places in America, nearly the only way to travel. But cars take up a lot of space (most of which is parking). Most places, that's a non-issue: We've mandated a 30-year supply of both roads and parking. But for anyplace that existed prior to those mandates (any main street, downtown or CBD more than 50 years old), those mandates didn't exist, and adding either lanes or parking requires demolishing buildings. 

We all understand that adding a lane for a block doesn't do anything. If it's going to do any good, it's got to go on for a good long while. So adding a lane for five miles requires acquiring five miles worth of front yards. And fighting with a few thousand property owners. And that's very difficult to do these days--lawsuits and lawsuit-induced delays are an inevitability. 

I've written previously about the extraordinary racism of urban highways, but here is the nut: the land was never cheap, the marginalized people it was taken from just lacked the legal rights to effectively contest it, and get a fair price for what was being taken. Where they did (DC) you'll find a near-complete absence of urban highways. 

Cars require a lot of land. They aren't making any more land. With fixed supply, as the demand rises, so does the price. So every bit of land devoted to cars is expensive and mandating that land be devoted to cars is just imposing a cost that, given free choice, people would not choose to pay.