Downtown in a Polycentric Region

This Joel Kotkin piece on downtown LA is about a month old, but I missed it and @720thruLA pointed it out recently.

Joel Kotkin’s latest dispatch pitches SoCal’s regional decline as the counternarrative to downtown LA’s renaissance, and posits that the regional story is more important.

To be honest, I agree with some of Kotkin’s writing about LA; my only major point of contention is that I’m much more optimistic about the value of our public transit investments. I’ve never met Kotkin, but in his writing he seems to genuinely care about the success of the LA region, which is obviously a primary concern of this blog. I think he raises interesting points, and want to explore some of the themes of the article in a little more detail.

Regional Decline or Regional Reorganization?

Economically, LA is somewhat unique among US cities – it’s partly coastal “knowledge” city, partly Rust Belt city, and of course partly the prototype Sunbelt city. LA isn’t as big as NYC, but it’s too big for a tech boom to have the same impact as it does in a boutique city like Boston or Seattle. LA’s manufacturing economy has suffered just as badly as any Midwestern city, but LA’s economy is much more diverse. Sunbelt cities have emulated LA’s growth, but none of them have reached the geographic extent where commuting across the entire metro region is impractical.

The result is a befuddling mix of high cost of living despite stubbornly high unemployment. One of the most troubling things about the LA metro area is that there has been zero net job growth for almost 25 years. Now, I’m no economist, but I think the use of 1990 as a benchmark coincidentally makes things look really bad for LA. In 1990, employment had just peaked from the 80s defense boom, and LA was about to take a double body blow from big cuts to defense spending followed by the enactment of NAFTA and other free trade agreements which, whatever you think about their macro impacts, have undeniably eviscerated US manufacturing.

Let’s go to the tape. If we index metro employment to January 1990, LA clearly looks worse than NYC, SF, and Chicago, and was even getting outclassed by the likes of Detroit until the financial crisis.

Ok, but here’s what happens if you net out manufacturing employment.

In that case, LA and NYC are basically on the same track, with SF and Chicago doing only a little better.

Now here’s what happen if you index to January 1994, when LA employment bottomed out from the early 90s recession.

How do you like them apples?

That’s not to excuse us from trying to address our economic problems like high unemployment, but it does provide some perspective. One interpretation is that LA is a region in decline compared to other major US cities. Another interpretation is that LA is dealing with the structural changes that those cities faced a few decades ago, but doing a better job of it than they ever did.

But Back to Downtown

In the context of those regional challenges, Kotkin frames residential growth in downtown LA as a footnote, since thanks to LA’s polycentric nature, the fate of downtown is not very relevant. He notes that despite the increase in people living downtown, surrounding neighborhoods lost more population, and office vacancies remain high. On Twitter, there was some pushback, saying that downtown is only in its infancy, while Kotkin treats it as an adult.

I sort of agree with both points of view. Downtown’s emergence as a desirable neighborhood is very recent, and rising residential rents and the boom of mid-rise and high-rise construction show that there’s still quite a bit of unmet demand. I also think that the “creative office space” market will eventually head east to downtown, where office rents are a little lower than West LA and firms can be in proximity to the urban amenities their young employees want, the same way that Silicon Valley’s boom has swept up the peninsula into San Francisco.

I will also note that while office vacancy downtown is high, it’s not atypical of the current office market in greater LA.

Now who thought Gateway Cities would come out on top!?

On the other hand, even if downtown’s population increases by an order of magnitude, it will still only be about 1% of LA County population. Current mainstays of the downtown office market, like the finance industry, have been reducing headcounts and office lease sizes. The most desirable office space in LA is Avenue of the Stars in Century City and Newport Center Drive in Newport Beach.

So in that sense, I agree with Kotkin that no matter what happens downtown, it won’t matter that much for the region. We already have over 13 million people in LA County and Orange County living and working with our current distribution of housing and employment. If you’re expecting the changes downtown to fundamentally alter the urban geography of Los Angeles, I suspect you’re going to be disappointed.

I also agree with Kotkin that subsidies for downtown hotels and the convention center are foolish – but that’s a general observation, not anything specific to Downtown LA. You can’t walk fifty feet in the halls of US city governance without tripping over someone who wants to dole out public funds to questionable projects like convention centers and stadiums. If you look for lodging downtown, you’ll find reputable places going for $150-$250 a night, with the chains, especially near the convention center, starting at $300 and up. If the market can’t build profitable hotels in a place where a new projects command $300/night with reliable occupancy, there’s bound to be some regulatory impediment in the way that could be removed. In fact, much of downtown’s boom is based on precisely that – eliminating regulatory boundaries through the adaptive reuse ordinance.

About That Transit Network

Unsurprisingly, my biggest disagreement with Kotkin is on transportation. He throws investment in public transit in the same boat as subsidies to private developers, and submits that a downtown-centered rail network is going to be ineffective in a polycentric region like LA.

On the funding side, self-help sales taxes have proven to be the only reliable way to get new infrastructure funded in California. It’s worth noting that over 2/3 of LA County voters have staked themselves to these projects being worthwhile for the future growth of the region. It’s also worth noting that 35% of Measure R funds go to highway infrastructure (20% for freeways and 15% local return to cities, which can use all of it on roads if they want). The major expansions on Kotkin’s beloved freeways, from the 5 in Norwalk Narrows to the 405 carpool lane to improvements on the 710, are all getting subsidized by sales tax money too.

On the rail network side, a downtown-centered system would be ineffective, but fortunately, that’s not what we’re going to get. There are major projects underway that don’t go downtown, like the Crenshaw Line, which will serve other important centers like El Segundo, LAX, and Hollywood (when it is inevitably extended north). Projects that are high priority for “Measure R2”, like a Sepulveda Pass/Westside transit line, will serve major destinations even further from downtown. And you could probably argue that two projects under construction that do go downtown – Expo Line Phase 2 and Westside Subway – bring more employment access benefits at their west ends in Santa Monica, Century City, and Westwood than they do downtown.

Downtown the Redeemer

A final point on which I completely agree with Kotkin is the uselessness of the East Coast journalist redemption narrative, where LA “unlearns the mistakes of its past”, builds a radial transit network, stops turning its back on downtown, and finally becomes a place that they deem worthy of calling a city.

I’m happy to see downtown’s growth, but it makes the lack of growth in other important regional centers that much more apparent. We do, as Kotkin says, need to boost jobs “from Studio City and Sherman Oaks to Boyle Heights, Leimart Park and Silver Lake”, and to do that we need to remove the regulatory barriers like residential downzonings and Prop U that stunted LA’s polycentric growth.

People have always refused to try to understand LA on its own terms, from HL Mencken calling it “Los Angeles the damned” to James Howard Kunstler writing about “its pervasive aura of doom”. Screw them. LA’s land use patterns already work pretty well, and Angelenos should be proud of their city. If we can overcome the challenges on land use, transit and polycentrism are going to work together better than post people expect. The challenges facing us are large, but there is tremendous potential in our region. Let’s get to work so that I can look forward to being able to say that all of LA’s centers, from Warner Center to El Segundo, Glendale to Long Beach, are creating opportunity for everyone.

LACMTA Ridership Update – April 2014

Another three months has passed, so it’s time for another LACMTA rail ridership update.

First, the raw data. Highlighted cells represent the top 10 months for that line.

Blue Line ridership recovered a little in April, but the Green Line and Gold Line had some weak months. The big surprise is a nearly 10% drop in weekday Red Line ridership since January. I suppose you could blame it on locking the fare gates, but the drop isn’t reflected in weekend data. Possibly, the data just isn’t accurate enough to see changes on this short of a time frame. Weekend ridership, with the exception of the Blue Line, remained strong.

The bright spot in the last 3 months of data was the Expo Line, which after leveling off for about 6 months, saw ridership gains between January and April. Expo Line is now within spitting distance of 30,000 riders a day.

Here’s the rolling 12-month average of weekday ridership:

Again, boardings per mile is a better way to look at productivity. Here’s the update for the rolling 12-month average of boardings per mile:

Another metric I’m interested in exploring is boardings per revenue mile. This is daily boardings divided by revenue miles of service provided, i.e. the number of trips multiplied by the length of the trips. (For the detail-inclined, I’m using boardings per revenue trip-mile, not per revenue vehicle-mile, because I don’t know what the consists are for every trip.)

I just started looking at this, so I only have a few months of data – let’s consider this the initial benchmark. Here’s the raw data and chart.

The subway is the clear winner in boardings per revenue mile, and I doubt that will change much when Westside Subway Extension is built. In fact, boardings per revenue mile may even go up because of the network effects.

For LRT, I find two interesting results in this metric. One, the Gold Line is the worst performer by a considerable margin. This is because LACMTA runs Gold Line Service just as frequently as the Blue Line, despite it not achieving even half the ridership. (Things wouldn’t look as bad on a vehicle-mile basis, because most Gold Line trips are two cars, while most Blue Line trips are three cars.) Now, you have to run service frequently so that riders can depend on it. But it does beg the question of why we’re running the Gold Line every 6 minutes during peak and every 10 minutes late night, while the Green Line achieves basically the same ridership with 7-8 minute peak headways and 20 minute late night headways. If the folks in Pasadena and East LA deserve 10 minute headways late night, why don’t the folks along the 105 corridor?

Second, the Expo Line is king – after only two years in service, it’s the most productive LRT line in boardings per revenue mile. This is partly due to the inexcusably poor peak period headway (12 minutes) which results in fewer trips on Expo Line than the Blue Line and Gold Line. But even if you assume Expo service is increased to Blue Line frequencies, you’d still get 11.92 boardings per revenue mile. If Reason wants to run a correction on its Expo Line hit piece, now might be a good time.

On a somewhat related note, you can’t beat my early AM carpool ride to downtown for convenience, but I do miss having firsthand experience on the rail system every day.

LAX Transit Part 2 – APMs and Ground Side Access

Via Curbed LA, LAWA has released a presentation on options for a proposed automated people mover (APM) and intermodal transportation facility (ITF). (Full report here.) Unfortunately, the results are a little disappointing. Slide 93 says that LAWA can accommodate Metro at any of four locations:

None of these locations are good transfer points for a future Sepulveda Pass transit line, which is high on everyone’s wish list. And earlier in the presentation, on slide 40, LAWA says that the only alignment that would connect to the Crenshaw Line station at Aviation/Century (the 98^th St alignment) has been discarded.

LAWA’s preferred APM option would cross the Crenshaw Line near Aviation and 96^th. From a stop spacing perspective, it would be undesirable to construct another station on the Crenshaw Line about 0.3 miles from Aviation/Century. A stop at this location might also prove to be costly, as it is presumably very close to the interlockings that will connect the Crenshaw Line mainline tracks to the maintenance facility and yard that will be built at the southwest corner of the rail corridor and Arbor Vitae.

That would still be better than LAWA’s preferred Metro connection at an ITF located at Airport and 98^th.

This option is very poor from a rail planning perspective. It sends through-riding passengers almost a mile out of their way and requires four small radius 90˚ turns in the space of about 1.2 miles, ensuring low operating speeds. It unhelpfully dead-ends the Green Line in a place with little demand other than the airport itself. It’s unclear what the service patterns would be, and if the Crenshaw Line is to split between the two routes, it would result in long headways at both the LAX station and Aviation/Century. It would require extensive modifications to Crenshaw Line infrastructure that’s currently under construction. And the price tag for this option would be high.

In short, it seems that the central question of an efficient connection between LAX ground side transport and LA Metro has still not been resolved acceptably. Perhaps the most telling graphic is all the way back on slide 8:

An airport, an ITF, and a consolidated rent-a-car (ConRAC) facility. And Metro out there. . . somewhere.

In all the options presented by LAWA, the locations of the ITF and the ConRAC are fixed. However, these are just buildings and parking garages, and as far as engineering goes, it’s easier to move them to the transportation lines than to move the transportation lines to them. Options with different locations for the ITF and ConRAC ought to be on the table.

So here are a few options that might warrant more investigation.

APM on Century, ITF & ConRAC at Manchester Square

This option would put the ITF and the ConRAC at Manchester Square, the eerie almost-empty half-mile square bounded by La Cienega, Aviation, Century, and Arbor Vitae, which LAWA has been slowly acquiring over the years. The APM would run along the south side of Century, with stops at Sepulveda/Century (Sepulveda Pass Line), Airport/Century (hotels), Aviation/Century (Crenshaw Line), and ITF/ConRAC.

Note: if you’re wondering why I’m showing the Crenshaw Line, Green Line, and future Sepulveda Transit Line this way, see the intro post on Sepulveda/LAX Transit and Upzone El Segundo.

This is more or less similar to the old LAX master plan circa 2007, which invited lawsuits from many adjacent communities. That plan was canned by Antonio Villaraigosa, who said he just wanted to move on, when he became mayor.

That history means this option has baggage, but it shouldn’t eliminate it as a candidate. Good routes are still good routes, and lawsuits can be defeated (see Expo Line through Cheviot Hills and Purple Line through Beverly Hills).

As I understand it, much of the unpopularity of the old plan stemmed from reconstruction of the runways that would have moved runways closer to Westchester and El Segundo. That reconstruction was purported to be necessary to add center taxiways between the two runways in each airfield. To be honest, I don’t know runways and air operations at all, so I can’t comment on that. However, I don’t think there’s any reason that the APM, ITF, and ConRAC can’t be separated out as their own project. If this is the best option for ground side access, it should move forward independent of more contentious proposals.

Advantages of this option:

• Proximity to the 405.
• Straight alignment for APM.

Disadvantages of this option:

• Puts Metro rail connections between ITF and Central Terminal Area (CTA), requiring Metro riders to drag their luggage onto the APM and check in at the terminal.

APM on 98^th, ITF at Airport and 98^th, ConRAC at Manchester Square

This option more or less follows LAWA’s discarded 98^th St alignment, adding a stop at Sepulveda/Century to connect with a future Sepulveda Pass transit line. The ITF and ConRAC would be located where LAWA proposes to locate them.

Advantages of this option:

• Proximity of the ConRAC to the 405.
• Acceptable alignment for the APM.

Disadvantages of this option:

• Puts Sepulveda Pass transit line between ITF and CTA, requiring riders to drag their luggage onto the APM and check in at the terminal.
• Puts Crenshaw Line east of the ITF, which makes it of little use to riders on that line as well, because they will still have to take luggage from the train to the APM.
• Poor access to the ITF from the 105 and the 405 results in challenging traffic engineering.
• Complicated construction (per LAWA) on 98^th St, but probably still easier than building a new Crenshaw Line station.

APM on Century, ITF at Sepulveda and Century, ConRAC and Auxiliary ITF at Manchester Square

This is my favorite option. The ITF would be split into two facilities, each offering full services. One branch would be located on the parking lot on the NW corner of Sepulveda and Century. The other would be located at Manchester Square, as close as possible to the NE corner of Aviation and Century. The facility at Aviation and Century would be configured to set back most of the garage from Century, allowing for more active uses (hotels, offices, etc) on the street. Direct ramps to and from the 405 and the 105 east would be provided to keep traffic off of neighborhood streets.

Advantages of this option:

• Allows direct access from both the Sepulveda Pass transit line and the Crenshaw Line to an ITF facility. Passengers would exit the train, check in and drop their bags, and then board the APM. No one would have to lug their bags onto the APM.
• Allows private transportation services to use either of two ITF locations, whichever best suits their service arrangements.
• This is the best option for both LAX-bound and through-riding passengers on Metro rail. The former get straight, quality routes, and the latter get a transfer that doesn’t require hauling bags all over creation.

Disadvantages of this option:

• Precludes any possible development of “Terminal 0” at the parking lot on the NW corner of Sepulveda and Century.

If we really want to roll out the red carpet for LAX passengers, LAWA should partner with the airlines, rental car agencies, private transportation operators, and hotels to direct baggage to the right destination for arriving passengers too. So when you check in to fly to LAX, you could have your bags sent to the ITF at the Crenshaw Line, or to the hotel, or to the ITF at the Sepulveda Pass Line, or the ConRAC, etc. This is just the sort of logistics problem that computers are supposed to make solving a snap, right?

Aviation/Century Station and Freeway Ramp Improvements

The environmental document plans for Crenshaw Line showed an auxiliary track in the middle of the station platform. I’m not sure if that’s still part of the plan, but if so, that track could be removed to create more space for vertical circulation to the APM and ITF/ConRAC. In any case, some modifications to this station will likely be necessary.

Freeway ramps to and from the 405 should also be rebuilt to provide direct access to the ITF/ConRAC, so that traffic doesn’t use local streets. I may revisit this issue in a future post, so stay tuned 😉

How to Write Your Very Own Pro-Sprawl Trend Piece

If you’re sitting around reading pro-sprawl opinion pieces by the likes of Wendell Cox and Joel Kotkin thinking, “sounds good, how can I get in on this action”, not to worry. There’s a simple template to follow, as demonstrated yesterday by an article in that venerable institution of urban research, Politico. This one was written by Robert Bruegmann, but it doesn’t really matter. Like 80s hair band power ballads, if you’ve heard one, you’ve heard them all.

Anyway, here we go. Items to include:

Generic comparison of cities that, in real life, have remarkably different urban forms: “Atlanta has wrested away from Los Angeles the distinction of serving as the poster child for sprawl.” Bonus points if you use two cities that I chose to demonstrate different types of suburbia.

Everything since 2007? Ignore ignore ignore: “Atlanta, over the last half century, has obviously seen its population and its economy grow faster than most of the older, higher-density, more transit-oriented cities of the United States or Europe.”

Talk about congestion but never mention VMT or transportation energy use per capita: “the greatest congestion and longest commuting times in this country. . . tend to occur in the largest and densest urban areas.”

Assert that transit doesn’t help the poor: “a major expansion of the transit system wouldn’t even benefit most people who can’t drive because the jobs are already so scattered around the metropolitan area, and the poorest people can’t afford the fares.” Oh, you can’t afford a car either? Welp.

Imply or state that expensive cities all have the same land use policies: “it is certainly not true of many of the highest-density places in North America – urban areas such as San Francisco, Vancouver, Toronto or even Los Angeles—where public policies aimed at curbing sprawl have led to sharply higher housing prices.” In fact, these four places have important differences in land use policy. Vancouver and Toronto are building new towers like crazy, and, especially in the case of Toronto, are cheaper than SF or LA. Vancouver, Toronto, and SF all have significant controls on suburban growth at the fringe, but in LA, you can build all the sprawl you want in the Antelope Valley, the Victor Valley, and Riverside County. I’m still waiting for someone to show me the policies in LA that are “aimed at curbing sprawl” other than maybe these things. Show me! SHOW ME!

Equate today’s dense first world cities with Third World slums and old law tenements: “every poor urban area in the world continues to have very high densities by historic standards, usually more than 50,000 people per square mile. On the other hand, every affluent urban area in the world. . . where urban densities often topped 100,000 people per square mile in 1900, in the Atlanta today the figure currently stands at an exceptionally low 1,800 people per square mile.”

Decry anti-sprawl efforts as unnecessary interference in free markets, while ignoring the reams and reams of regulation that enforce suburban development patterns: “as people have become richer they have demanded more space, and they have gotten it everywhere there has been a truly democratic government and anything resembling a free market in land.”

Studiously avoid mention of any other “historical background” that might explain why US cities started decentralizing in 1950 and why Southern cities in particular are very spread out: “this historical background helps explain why Atlanta, as a city in the affluent world that has done most of its major expansion fairly recently, is such a sprawling place.” You don’t need me to spell this one out for you, right? Wink, wink.

Notably on-point critique of a lot of anti-sprawl activism: “it has been a conspicuous fact of urban life that many of the same people who deplore sprawl at the edge are also determined to preserve the character of their existing neighborhoods in the center.” Credit where credit is due, right? We’re looking at you, Westside, Marin County, San Francisco, and Peninsula.

Ignore international examples like Japan when they might be inconvenient for your narrative: “strident efforts to reverse the course of urban history and push these places back into the mold of dense 19th-century cities heavily dependent on public transportation risk destroying the very things that have made them such magnets for population and economic growth in the first place.”

Easy, right? Crank out a few of these and see if you can’t get a job at Reason or Cato.

To be honest, I wish the criticism of anti-sprawl activism and smart growth was, well, smarter. If you read O’Toole, Kotkin, and Cox regularly, you’ll find that they do make good points. But you have to sort through a lot of junk to find them. In a way, the criticisms of dense development are a lot like the “pop urbanist” analysis of cities – unwilling to understand and think about each city on its own terms. One side will tell you that you need more freeways and subdivisions. The other side will tell you that you need streetcars and high-rise development to attract the creative class or Millennials or whatever we’re calling young people with money now. If they say anything helpful, it’s almost coincidental.

Cities are complex. To have any chance of understanding them, we have to be willing to set aside any worries about what a city should look like, and study how they work (or don’t work). And we should be willing to learn from anywhere, but also willing to accept some lessons may not apply. Assuming that all cities have the same problems which have the same solutions is bound to result in recommendations that are embarrassing – or at least should be.

Air Rights Dreaming

As land available for development in core urban areas grows scarce, some cities have started to look to the air rights above transportation facilities, such as rail yards and freeways, as potential locations for growth. Unfortunately, building over this infrastructure, especially rail yards, only makes sense for high-margin projects in very built-up areas. To see why, let’s take a look at some existing air rights projects, and explore the challenges that confront the engineering for such projects.

NYC: PSNY & GCT

No North American city is more air-rights crazy than New York. After all, air rights are practically baked into the city’s DNA: before zoning restricted building heights, it was common for developers of tall buildings to buy the air rights over adjacent shorter buildings to protect views from future construction.

New York is also home to two of the most widely-known rail yard air rights developments: Penn Station/Madison Square Garden and Grand Central Terminal. Given the success of those projects, it would seem to make sense that overbuilds at Hudson Yards, Atlantic Yards, and Sunnyside Yard would be viable.

However, as we’ll see a little bit later, PSNY and GCT had a big advantage in that the overbuilds were planned, designed, and constructed at the same time as the rail facility. They’re also located in very desirable parts of Manhattan, where rents justify the cost of decking over the rail yard. Atlantic Yards isn’t in as good a location, and the developer has taken stunning losses. Sunnyside Yard is worse, surrounded by low-rise residential and low-rent industrial space; there’s no way rents in the area would justify the cost of decking. Meanwhile, at Hudson Yards – the one location where the market might support private development of air rights – the city seems intent on forcing commercial development, while the market wants residential.

Update: as True Urbanism pointed out on Twitter, Madison Square Garden was of course built well after the original PSNY. Construction would have been complicated by building over an active railroad (though facilitated by the fact that the railroad itself was doing the construction and was desperate for money). Building over platforms offers something of an advantage in that you have a place to put columns.

Boston: Turnpike & NEC

Projects in Boston have not fared much better. In 2008, after wrangling significant tax subsidies out of the city and state, and fending off the predictable NIMBY challenges, the Columbus Center was set to begin construction over the Massachusetts Turnpike and Northeast Corridor east of Back Bay Station. Then the financial crisis hit, and the main investor (CalPERS, of all people) pulled out. The project has gone nowhere since, with developers in downtown Boston focusing on easy to redevelop parking lots in the Seaport District.

Further east, the South Station Tower was another victim of the financial crisis and shows no signs of life, despite being planned for during the reconstruction of South Station in the 1980s. Further south, plans have been floated for Northeastern University to bridge the gap between Back Bay and Roxbury by building over the NEC, but the university has consistently held these plans to be nonviable. And further west, the first part of John Rosenthal’s Fenway Center project is seeking subsidies as well.

The marquis air rights projects in Boston – the Prudential Center and the various cap parks on the Southwest Corridor – were all built, like PSNY and GCT, concurrent with the construction of the transportation facility. The Prudential Center was built in the 1960s at the same time as the freeway, at a time that railroads were desperate for money. When the Southwest Corridor was built, all rail traffic was temporarily diverted onto the Fairmount Line. Only Copley Place was built over active rail and after the Turnpike was open, and to be honest, I’d love to know how they pulled it off.

Freeways

Out in Chicago, there’s the famous post office building, that the 290 goes straight through. The building, however, predates the freeway – it was completed in the 1920s and the post office didn’t open until 1933. The building was designed with passageways left for the road.

In New York, you have the brutal Robert Moses high-rises over the Cross Bronx Expressway, also built at the same time as the freeway. Moses proposed a similar concept for the never-built Mid-Manhattan Expressway.

Engineering Matters

So why is it so expensive to develop the air rights over active transportation facilities? A few engineering and construction challenges come to mind.

First, from an engineering perspective, you have a very unusual and highly constrained site. Next time you see a high-rise under construction, check out the amount of space between the columns. You’ll probably see it somewhere around 30’, in a rectangular or square pattern. This spacing keeps the bending moment in the beams small. (Bending moment is the force that tries to snap beams the way you’d snap a twig.)

But 30’ is only enough space for two lanes of traffic, or two rail tracks on very tight spacing. To span a four-lane freeway or four rail tracks you’d need at least 50’, again assuming no room to spare. Bending moment in a uniformly loaded beam scales with the square of the length of the beam, so a 60’ beam would have four times as much as a 30’ beam. That means you need big honkin’ beams, very strong joints to transfer the load to the columns, and big ol’ columns to take that load to the foundation. All of that costs money.

It’s also hard to fit a rectangular pattern of columns onto an existing transportation facility. Freeways tend to curve and have on and off ramps. Rail yards are worse, because if the yard wasn’t built with future air rights development in mind, it’s unlikely there’s enough room to fit columns between the existing tracks. If there’s nothing between tracks, they’re often build between 13’ and 16’ apart. At 13’ there’s essentially no useful space between the tracks. At 16’, if the rail operator is feeling extremely generous and gives you 7’ clearance, you could squeeze in a 2’ column. More likely, you need 18’ to 20’ between tracks to get columns in there. That leaves you two costly options: rebuild the rail yard before you construct the building, or go with very long spans between places where you can get columns in based on the existing geometry.

On top of all of that, you have to deal with turnouts and crossovers. Let’s say you have a column line between two tracks that are 18’ apart. A crossover between those two tracks, even a low speed one, is going to preclude any columns on that column line, probably for at least 150’. Of course, if you were planning to build over a new rail yard at the same time you built the yard, you’d modify the track design to make things easier for yourself – that’s why it was so much easier to build PSNY and GCT. But Sunnyside wasn’t planned that way, and it would be a big problem for the structural design.

For example, consider this hypothetical yard with 6 tracks and 2 ladders (crossover tracks). The red squares show column spacing. That big gap in the middle is a big money pit.

Second, after you design all of this, you’ve got to get it built, over an active transportation facility. Once the project gets above the deck level, things get easier, but building the deck itself is very costly. Consider, for example, Sunnyside Yard. You can’t be drilling and pouring foundations, or erecting columns, six inches away from tracks with trains running on them. Nor can you be hoisting and setting massive steel beams for the deck over tracks with trains running on them. That means all the work has to be done at night.

But there’s still activity at the rail yard at night, so you can only work on parts of the site at a time. Your work window might be, say, 10pm to 5am. That doesn’t mean you start working at 10pm, that means the railroad starts the process of giving you a work zone at 10pm. So the area has to be cleared of trains, and then the electrification has to be shut down and confirmed to be grounded. You work from maybe 11pm to 4am, and then you have to give the track back so that the railroad can make sure it’s ready to be put in service by 5am. And if there are service disruptions or maintenance issues, nuts to you – the dispatchers and maintainers are going to worry about restoring service first, and you might not get any work done.

A transportation air rights project also probably faces a common challenge in urban construction – lack of lay down area, or space to store construction equipment, machinery, and material. That means that every day, you have to bring that stuff in from elsewhere, which also takes time and money.

Add all of that up and you’re looking at a complicated, costly design, and complicated, costly, inefficient construction. These types of projects do make sense in some places, but you have to be able to get high returns to justify them.

What Are We Trying to Accomplish?

As always, it’s good to take a step back and look at our goals. What are we trying to accomplish, in terms of the development of the city, with these projects? There’s a saying among engineers: we can design anything you’re willing to pay to build. The question is if it’s worth building it.

In densely-developed Manhattan, it seems possible that some type of project should be able to make a go of it at Hudson Yards without tax subsidies. But Sunnyside Yard, adjacent to low-rise residential and industrial land? Projects over the Massachusetts Turnpike adjacent to parking lots in the South End or single-family housing and duplexes in Lower Allston? There’s no way those projects are economically viable, not without allowing a ton of development and providing big-time subsidies. It’s telling that in the North American city with the biggest boom in tower construction, Toronto, there are zero projects being built over Go Transit’s trunk line downtown, despite proximity to high rent areas and the lakefront.

A few days ago, Market Urbanism tweeted that the lengths to which people will go to preserve low-density residential development are incredible. And that’s what’s really going on with most air rights projects, as well as a lot of other trends in urban development. People would rather subsidize air rights projects to the tune of tens of millions of dollars – or pretend that air rights projects make sense without subsidies – than allow more development in existing neighborhoods. But that’s a really inefficient use of taxpayer money. If the goal is to create more housing, those subsidies would go much further at boring, simple construction sites. Air rights projects might sound exciting, but the costs should be left for the private sector to incur in places where they really make sense.