Does Elon Musk Understand Urban Geometry?

He may be a brilliant visionary in all kinds of ways, but Elon Musk’s “Master Plan, Part Deux” makes grand plans for the abolition of fixed route transit without thinking clearly about urban space:

With the advent of autonomy, it will probably make sense to shrink the size of buses and transition the role of bus driver to that of fleet manager. Traffic congestion would improve due to increased passenger areal density by eliminating the center aisle and putting seats where there are currently entryways, and matching acceleration and braking to other vehicles, thus avoiding the inertial impedance to smooth traffic flow of traditional heavy buses. It would also take people all the way to their destination. Fixed summon buttons at existing bus stops would serve those who don’t have a phone. …  (Emphasis added)

Musk assumes that transit is an engineering problem, about vehicle design and technology.   In fact, providing cost-effective and liberating transportation in cities requires solving a geometry problem, and he’s not even seeing it.  In this he’s repeating a common delusion, one I hear all the time in urbanist and technology circles.

Musk’s vision is fine for low-density outer suburbia and rural areas.  But when we get to dense cities, where big transit vehicles (including buses) are carrying significant ridership, Musk’s vision is a disaster.  That’s because it takes lots of people out of big transit vehicles and puts them into small ones, which increases the total number of vehicles on the road at any time.  The technical measure of this is Vehicle Miles (or Km) Travelled (VMT).

Today, increasing VMT would mean increased emissions and increased road carnage, but let’s say technology has solved those problems, with electric vehicles and automation.  Those are engineering problems.  Inventors can work on those.

But there is still, and aways, the problem of space.  Increasing VMT means that you are taking more space to move the same number of people.  This may be fine in low-density and rural areas, where there’s lots of space per person.  But a city, by definition, has little space per person, so the efficient use of space is the core problem of urban transportation.

When we are talking about space, we are talking about geometry, not engineering, and technology never changes geometry.  You must solve a problem spatially before you have really solved it.

The reigning fantasy of Musk’s argument is that we must always “take people all the way to their destination.”   To do this we must abolish the need to ever change vehicles — from a train to a bus, from a car to a train, from a bus to a bike — and of course we also abolish walking.  This implies a vision in which buses are shrunk into something like taxis, because a vehicle going directly from your exact origin to your exact destination at your chosen time won’t be useful to many people other than you.

So a bus with 4o people on it today is blown apart into, what, little driverless vans with an average of two each, a 20-fold increase in the number of vehicles?   It doesn’t matter if they’re electric or driverless.  Where will they all fit in the urban street?  And when they take over, what room will be left for wider sidewalks, bike lanes, pocket parks, or indeed anything but a vast river of vehicles?

There are audiences for which Musk’s vision makes perfect sense, people for whom useful high-ridership transit isn’t an option anyway.  There are two big categories of these people:

  • People who live in outer-suburban and rural areas, where space is abundant and high-ridership transit isn’t viable.
  • The top 20% or so of urban residents, who can afford to use relatively expensive services that would never scale to the entire population of the city.

If you are in one of these categories, your most urgent task is to remember that most people aren’t like you, and that cities are impossible if everyone lives according to your personal tastes.  As Edward Glaser said, “one’s own tastes are rarely a sound basis for public policy.”

That issue, right there, is the great disconnect between tech marketing and genuine urban problem-solving.

Tech marketing is all about appealing to elite personal tastes.  It runs on the assumption that whatever we sell to the wealthy today we can sell to the masses tomorrow.  But some things stop working when everybody buys them.  Cars in dense cities, for example, are not a problem when only the top 20% are using them; it’s mass adoption of cars that makes them ruinous to a dense city and to the liberty of its citizens.  Ask anyone in a fast-growing developing world city about that.

Here is the harm that this all this elite chatter about abolishing the bus is doing:  It’s introducing fatal confusion into the discussion of urban development.

Dense cities that want to live in the real world of space and time, and that do not want to become dystopias that are functional only for the rich, need to use urban space efficiently.  There is some simple and well-proven math about how to do this, which is also the math of how transit systems achieve high ridership.

These cities need to organize themselves around frequent transit corridors, where big-vehicle frequent transit, bus or rail, can prosper, allowing the city to grow dense without growing vehicle trips.

Someday some of these corridors will be rail or Bus Rapid Transit.  But the only way to grow enough corridors quickly, so that you cover much of the city with frequent service that can succeed in ridership terms, is to take frequent fixed-route bus service seriously.  If you don’t do that in your land use planning, you’re going to end up building a city where fixed transit is geometrically impossible, and then you’ll have to settle for Musk’s vision.  Geometrically, that vision can only mean liberating transportation just for the top 20% or electrified, automated gridlock for everyone.

Smart cities aren’t just the ones that chase the latest technology fads.  They’re the ones that think carefully about the spatial, geometric problem that a dense city is.   Because if it doesn’t work geometrically, it doesn’t work.

 

 

New York: “Subway Deserts” and the Bus “Turnaround” Campaign

It’s fun to draw maps of “deserts,” places where some cool thing is absent and where you can therefore imply that people are being abandoned or ignored.  This Chris Whong map of  New York “Subway deserts” for example, just showed up in Citylab:

Source: Chris Whong

Source: Chris Whong

Sure enough, most of the land area of New York city is not near a subway station.

But how many people is that?  It’s a lot of people, but fewer than you’d guess from looking at the map, because so much of the subwayless area is low-density or even open space.  Geographically accurate maps always invite you to misread area as population.

And in any case, should everyone in New York be close to a subway stop?  The subway is not the whole transit system; it’s just the high-capacity backbone of it.  You build subways only where you expect to fill long trains at high frequency for much of the day.

There may be places in New York that would profit from, and reward, the investment in a subway, but a map of everywhere that subways don’t go doesn’t even start that conversation.

The deserts that really matter are deserts of access, places where people are truly without options.  And to assess that for New York, even just for transit, you’d have to care about the massive bus network.  It’s the bus network job to cover the whole city, getting close to everyone.  Much of the bus system is also very frequent.

That’s why the smart folks at TransitCenter — a New York – based transit advocacy foundation — have launched a Turnaround campaign, meant to call attention to all the things that can be done to make New York bus service more useful, so that almost everyone can get to useful transit.  I deal with the barriers to good bus service all over the developed world, and the problem is always the same.  It’s not the technical limitations to what buses can do.  It’s the official apathy about them.

For example, many elected officials still believe that because buses are supposedly “flexible” they should just be changed so that they go by the house of anyone who requests them, as though fixed route bus lines were taxis or UberPools.  If they get enough phone calls, these elected officials will tell staff to transform the route on the right into the one on the left, with no comprehension of what they’re destroying.

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Obviously, bus lines designed for high ridership run straight, so that they are as useful to many many people as possible, and so that they can run as frequently as possible.  Obvious stuff, but you have to fight this battle over and over, and that’s a lot of what I do.

So bravo to TransitCenter for its review of the New York buses.  It’s something that people in any developed-world city would be smart to review, and contemplate.

Job! Manager of Access Planning in Vancouver

It closes July 20, so act fast.  Greater Vancouver (Canada)’s transit agency TransLink seeks a Manager of Access Planning, where “access” refers to people with disabilities.  The listing is here.

 

Does the History of a Technology Matter?

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Mater Hill busway station, Brisbane

Ben Ross has a nice long read in Dissent about the history of Bus Rapid Transit, noting all the ways it’s succeeded, failed, and been co-opted by various non-transit agendas.  He’s especially interested in the way various petroleum-and-asphalt interest groups have supported BRT as an alternative to rail for reasons that probably don’t have much to do with their love of great public transit.  All this is worth reading and knowing about.

But what, exactly, should we do with this history?  Practically everything that breaks through into the public discourse has private public relations money behind it, and that money always has different goals than you and your city do.  That’s why you should always lean into the wind when reading tech media.  But just as it’s wrong to fall for everything you read in corporate press releases, it’s also wrong to reflexively fall against them.  (Cynicism, remember, is consent.)

Galileo paid the bills, in part, by helping the military aim cannonballs correctly.  Does that mean pacifists should resist his insight that Jupiter has moons?

So while I loved Ross’s tour of the history, I reject his dismissive conclusion:

Buses will always be an essential part of public transit. Upgrading them serves urbanism, the environment, and social equity. But a better bus is not a train, and bus rapid transit promoters lead astray when they pretend otherwise. At its worst, BRT can be a Trojan horse for highway building. Even at its best, it is a technocratic solution to a fundamentally political problem.

The term technocratic is really loaded here.  Given the new “revolt against experts” trend in our politics, we urgently need to recognize  hard-earned expertise and to distinguish it from elite selfishness, but technocrat is a slur designed to confuse the two.

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RBWH busway station, Brisbane

There are some great bus rapid transit systems out there, and not just in the developing world.  The mixed motives that underlie BRT advocacy don’t tell us anything about where BRT makes sense, any more than the mixed motives behind rail advocacy do.

A light reading of history can help you recognize the prejudices that may lay behind advocacy on all sides.  But then you have to set that aside, and think for yourself.

 

Riding Against the Grain: A Photographer on Portland’s Line 75

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Portland-based photographer Geoffrey Hiller is best known for a marvelous book Daybreak in Myanmar, which interleaves pre- and post-revolution images of that country.  Now he’s turned his attention to one of Portland’s most interesting bus lines — at least in terms of the diversity of unsung corners of the city that it serves, and the beautiful and often eccentric people who live and do business there.   His blog lays out the work in little photo vignettes with commentary.  It’s wonderful.

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I did an essay for his blog and any future book, in which I say things like …

As it makes its long orbit around Portland, then, the 75 tours the shifting front lines of many epic struggles. Gentrification loves the bohemian but chases it away. Defenders of history scream “stop demolishing Portland!” even as a desperate need for housing calls for bigger buildings. And in parallel, everywhere on the 75, you can watch the parallel dramas of power and weakness: power struggling to protect itself, while others struggle for survival and dignity.

To this shifting landscape, Geoffrey Hiller is the perfect guide. He knows you’ve seen the real estate photos, the chamber of commerce photos, the tourist photos, and the photos of cashed-up millennials in designer grunge luxuriating in sculpted authenticity. He wants you to see something else. Here is the Portland in between things, the struggling and hopeful Portland, the Portland that’s happening anyway despite everyone’s grandest plans.

You might find it a useful accompaniment to Geoff’s photos.  It’s all about a Portland you may have missed in your perusing of real estate magazines, or for that matter your urbanist-guided tour.

 

All photos: Geoffrey Hiller

Well-intentioned U.S. Frequency Analysis Causing Needless Angst

The best of intentions lay behind the recent analysis of the availability of high frequency service, described by Jake Anbinder at TransitCenter.  And as one of the original proponents of Frequent Network branding, I’m delighted to see organizations starting to care about whether transit is useful, rather than just whether it exists.

But when we transit professionals design Frequent Networks and their standards, we think really carefully about what counts as frequent service.  I insist that it always means every 15 minutes or better on both peaks and throughout the midday, but we have to have a sensitive local conversation about how late it extends into the evening, and how long on weekends.  It’s easy to say that you want 15 minute service 24 hours a day, but when you look at your fixed resources, you’ll find that if you insist on that, your Frequent Network won’t cover enough of your city to be either useful or politically feasible.

That’s exactly the problem that makes the analysis misleading.  Here’s the chart making the rounds from the their work:

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The problem is that this analysis defines frequent transit as 672 trips each direction per week on a route segment.  Why 672?  It’s 4 x 24 x 7, that is:

  • 4 trips per hour (so every 15 minutes)
  • 24 hours per day
  • 7 days per week.

For service to count as frequent, by this analysis, it has to be frequent even at 3:00 AM.  

I can’t think of a bus route anywhere in North America that runs every 15 minutes in the middle of the night.  Maybe there are a few in Manhattan, but this calculation is an unrealistic basis for defining Frequent service anywhere in North America, except for the densest, biggest cities..  (Obviously, the other way to meet this target is to be very, very frequent during the day to compensate for not being frequent at night.)

Why quibble about this?  Because this chart caused some needless angst in the media.  Among its worst outcomes would be to signal that frequent service is such a rarefied thing that most cities couldn’t realistically hope for it.  It certainly obscures all the great work that’s actually being done to build realistic but useful frequent networks in many cities.

For example, it triggered this Houston Press article implying that there’s some racial disparity in the distribution of frequent service, based on the bizarre notion that Houston’s frequent service consists only of the areas highlighted in yellow:

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The Press’s Megan Flynn writes:

In Houston, according to TransitCenter’s analysis, while nearly 80 percent of people have access to transit at least a half mile away from their doorstep, only 18 percent of them have access to what the map’s algorithm considers the highly reliable, “high-frequency” service.

By the AllTransit definition of high-frequency—service running at least every 15 minutes on average, 672 times a week—only one bus route, the Westheimer route, meets that standard, along with all three of Houston Metro’s light-rail lines.

As TransitCenter noted in its analysis: “Notably, in cities with fewer high-frequency transit lines there tends to be a greater demographic skew among people who live near quality transit.”

And it considered Houston to be one of the two “most notable” examples of that demographic skew.

Even though black and white people in Houston each have equal walking-distance access to public transportation in general—each making up 24 percent of the pie—36 percent of white people can access high-frequency service while only 19 percent of the black population can. Latinos make up 45 percent of people with walking-distance access, yet only 34 percent access high-frequency routes. (See The New York Times‘s map of the racial makeup of Houston’s neighborhoods here to compare with the above map.)

Ouch!  Great basis for rage.  But  it’s not about what matters!  When we designed the Houston network, our standard for frequent service was not 672 buses/week, and the map above illustrates why.  If it had been, we’d have brought frequent service to too small a part of the city, and we could have fairly been accused of racial disparity.  That’s why we didn’t!

As it is, the Houston Frequent network (the red lines on this map) is abundant and citywide.   It may not fit some abstract big-city standard, but it’s the fair and equitable way to cover most of Houston with frequent service given the transit agency’s resources, and it’s sculpted to hit inflection points on the frequency spectrum where ridership begins to take off.  The same is true of many of the cities that “fail” the 672 buses/week test.

TransitCenter is an excellent organization, by the way, and this showed in how open they were to this critique when I shared it in draft.  In our correspondence they asked me what a good benchmark would be.  I suggested “15-15-7”:  15 minute frequency, 15 hours a day, 7 days a week, plus 30 minute service for an additional 5 hours a day.  That gives you a total service day of 20 hours, e.g. 5:00 AM – 1:00 AM.  That’s only 490 bus trips/week, so their estimate of 672 is high by over a third.  The chart would be totally different, and more useful at motivating change in cities that aren’t as dense as New York or San Francisco, if a standard around there had been used.

Jobs: Transit Planners in Auckland and Brisbane

MRCagney, the leading public transport/transit planning firm in Australia and New Zealand, is hiring senior planners in Auckland and Brisbane — both really cool places to live!  Details here.

I worked for MRCagney directly during my five years in Australia, and we retain a close bond with them, teaming often on projects in their part of the world.  Get this job, and you’ll probably end up working with me at some point …

 

Core vs. Edge Debates in Public Transit

In just about every North American regional transit debate I’ve ever been involved in, someone has said:  “Why is all this money being spent on transit downtown!  Downtown already has lots of transit, while out here in ___, we have nothing!”

If this is a debate within a city — often between city councilors who represent districts — then they’ll say this about downtown, and sometimes about dense inner neighborhoods around it.  But exactly the same debate happens at another scale: among municipal governments in a huge urban region; in that case, they’ll complain about the entire dense, old, transit-oriented city at the region’s center.   In either case, I’ll use the term core to mean the older, denser, inner area in this debate, and edge to refer to the newer, less dense, more car-dependent area.

Either way, the debate sounds like this:

Edge:  “The core area has so much transit, and we have little or nothing, but we pay taxes too, so why does so much of the money go to the core?  Also, we’re trying to build denser development in more transit-oriented ways, to start moving beyond car-dependence, but how can we do that without good transit?  We’re desperate out here!

Core:  “It’s great that you want to be denser, but we’re already very dense.  That means a much bigger share of our residents need or want transit, and our ability to grow and thrive depends on it.  Car-dependence just isn’t an option at our density, so if transit doesn’t work, our city doesn’t work.   We’re desperate in here!

I sympathize with all sides, and do my best to warn all sides away from this kind of parochial polarization.  Nothing is sadder than coming into a city or region with inadequate transit, and finding that the locals are more interested in blaming and resenting each other than in working on a problem they all share.

Once more with feeling: Transit is a network, which means that its parts are interdependent.  You cannot think about it the way you think about libraries or fire stations, where putting one in a certain place mainly benefits the people there, because the whole network affects everyone’s ability to get everywhere.  So when folks argue that the another part of the network should be weaker so that theirs can be stronger, they’re actually undermining their own transit service.

In North America, the edge tends to have the votes to win edge-core debates, so it’s not surprising that many North American transit networks are weak at the core.   When you look at North American rapid transit systems, you often notice pieces missing in the middle.  Metro Vancouver is one of the most dramatic cases.  Look at what happens at the west end of the yellow line:

vancouver skytrain with gap

It never ever makes sense for a major rapid transit line to end just short of where it would connect with another major line, as the yellow line does here.  This gap creates all kinds of overloading problems, as three suburban branches from the east all feed into a single line into downtown (the northward peninsula).  It obstructs many cross-regional trips, most obviously from the eastern suburbs to the airport (on the island in the lower left).   Finally, the bus line that crosses this gap is one of the busiest in North America, the best signal of all that you need a rail line.  Yet if you listened to the regional transit debate, you’d think that plugging this gap in the whole region’s network is a project “for Vancouver” just because the gap itself happens to be in Vancouver.

Once you learn to recognize it, you’ll see this theme in city after city.  Missing links like Vancouver’s are an extreme example.  More common is a persistent disinvestment in the core parts of a network even though people from the whole region rely on those parts.  Many big city transit networks end up massively overcrowded and failing at the center even as the political pressure is all about extending further toward the edge.

Fortunately, a few North American regions are showing real leadership and progress on this:

  • Toronto is under political pressure to extend its subway lines further into the suburbs, adding even more riders, even as the inner segments of the network are severely overloaded.  Where would all those passengers fit?  The only solution is another subway through downtown, but as soon as you mention downtown, a majority of the City Council has had trouble seeing why they should care.  Major progress has been made on advancing this crucial “core-strengthening” project in the last year.
  • Los Angeles Metro is building its Regional Connector project, a new subway under downtown whose purpose is to hook together rail lines that now terminate on opposite sides of downtown, never touching each other.  For long trips across the region — from Pasadena to South LA, say, or from Santa Monica to East LA, the connector replaces two-transfer trips with zero-transfer trips (which means it also replaces three-transfer trips with one-transfer trips), so it dramatically increases the ease with which you can get across the larger city.  LA Metro produced a very smart map with wide two-way arrows showing these improved regional flows. The agency did a great job of helping people see that while the project is in downtown, it’s for the whole city and region
  • Last month, there was major breakthrough in the Seattle area.  The Sound Transit 3 regional rapid transit proposal, which will go to the voters in the fall, requires a new subway tunnel under downtown, parallel to the existing one two blocks away.  Until last month, the entire cost of this tunnel was considered a Seattle expenditure, so it completed for funds with other city projects.  But of course, Seattle doesn’t need another subway tunnel two blocks from the existing one.  It’s the whole region that needs it, to fit all of the region’s rail lines through Seattle.  So the final plan, correctly, treats this is a cost to be shared across the region.

Finally, why have I said “North American” throughout this post?  Because most other wealthy countries I’ve worked in or studied don’t have this issue to the same degree.  Mostly this is because those countries have located regional transit planning at a level of government that has the power to see and act on a citywide vision, and account for all of its consequences.  Typically, this power is integrated with the other great powers that act on that scale, such as land use planning, infrastructure, and so on, so that the implications of each action can be accounted for.

Good planning can still happen in a more fragmented political context, though, so long as someone has the power and skill to make the argument for a complete network vision.  Fortunately, this is happening more and more.

The Chinese Straddle Bus is Back

Yes, the Chinese straddle bus is back.  “Back” because you read about it here six years ago.  A wide flat vehicle that spans the travel lanes of an expressway, so that cars can drive under it.  As I observed back then, its most interesting feature is the way it collapses what little remains of the difference between bus and rail.

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And yes, if your starting point for urban design is that single-occupant cars, despite their extreme inefficiency in using scarce urban space, should be allowed to go anywhere at all, and that the surface plane should be designed solely for their convenience to the exclusion of all other citizens and needs, then this technology makes sense.

Remember, the primary cost of transit infrastructure is the cost of keeping transit out of the way of motorists, on the assumption that motorists have the prior claim to absolutely every bit of public space in our cities.

Meanwhile, Cap’n Transit has the best parody.  Not that I don’t take this seriously, at least as a scalpel for prying open the deep assumptions of infrastructurism.

What are Transit Consultants For?

JWlogoSquareThis is going to sound a little like marketing, but it answers a common question or objection.

Why do you need consultants for your city’s transit plan?  Other consultants will speak for themselves, but here’s why you might need a consultant like me.  Inevitably, this list is also a definition, in my mind, of what makes a good consultant, at least for transit network design.  It’s what we strive for at our firm.

  • Experience with Lots of Cities.   Your city is unique, but the facts of geometry, the facts of biology, and many human longings and foibles are the same everywhere, even on other continents. I’ve worked in (or studied) about 100 cities and towns, so I can see exactly what’s unique about your city and exactly what’s just like everywhere else.  This perspective is really helpful to locals, who don’t all get to make that comparison every day.  In particular, I can help you take some of the fervor out of local arguments by pointing out that many cities, at this moment of history, are having the very same conversation, featuring the same points of view.
  • Ability to Foster Clear Conversations.  Because of that experience, we cut through a lot of angry chaos in the local conversation, and frame questions more constructively.  This doesn’t mean we make hard decisions go away; in fact we often make them starker.  But we also make them clearer, so that if the community makes a decision, they actually understand the consequences of that decision.
  • Maximizing Your Community’s Options.  Unlike a lot of consultants, we hate telling communities what they should do.  We prefer to show them what their options are, and let them decide.  But laying out options is really hard.  You have to show exactly where the room to maneuver is where where it isn’t.  That requires the next two skills.
  • Clarity about Different Kinds of Certainty.  As consultants, we know when we’re in the presence of a geometric fact rather than a cultural assumption or a personal desire.  Only when we accept the facts of geometry (and biology, and physics) can we know what a community’s real options are.
  • Ability to Argue from Shared Values.  Good transit consultants don’t just talk about peak loads and deadheading and value capture and connection penalties.  They also talk about liberty and equality and durability and prosperity and aesthetics.  Then, they explain why those big ideas for your city imply that you should care about this or that detail of your transit system.  It may turn out that connection penalities are an important issue if you care about liberty and opportunity, but your consultant should be able to explain why.
  • Skill at Synthetic Thinking.  Synthetic thinking is the ability to generate insights that solve many problems at once, such as you need to create a scientific theory or design any complex system.  Synthesis means “putting things together,” so it’s the exact opposite of analysis, which means taking things apart.  Synthesists rely on the work of analysts, but you will never analyze your way to a good network design.  The skill of synthetic thinking is impossible to teach and can only be recognized where it appears, but a fondness for thinking abstractly or theoretically is a good indicator of it.  And since network design is rarely taught in universities anyway, the best evidence of this skill is a track record of having done it successfully, in lots of cities, plus (very important) the ability to explain it to a diverse range of people.
  • Skill at Spatial Thinking.  Finally, the specific kind of synthetic thinking needed for network design is spatial.  People who like designing and solving problems in space — architects, military strategists, chess players, visual artists, and kids or adults playing with trains — are likely to be good at it.

The  biggest transit authorities, in the most transit-sophisticated cities, may have people with all these skills on their staff, because they are questioning and improving their network all the time.  But most transit agencies don’t, and that’s understandable.  In most cities, you don’t redesign your transit network every day, or even every decade, so it’s inevitable that most of the staff of the transit agency has never done it before.  Relatively few transit agency jobs require, on a day-to-day basis, the skills that make for good network designer, especially for large-scale redesign.  So those agencies will benefit from some help.

Consultant, of course, is a much-sullied word.  For one thing, many consultants go around telling people what they should do; we do this as little as possible.  Many consultants just teach you to envy other cities, which appeals to certain human desires but is also not the best basis for good decisions.  Also, like professionals of any kind, some consultants speak in ways that are incomprehensible to most people, or refuse to explain things clearly, so as to sound wise or authoritative.  (“Our proprietary six-step model with a Finkelstein regression says you should build this freeway.”)   A transit consultant who can’t make a reasonably intelligent and open-minded person understand their work isn’t one you should trust — especially when it comes to network design.

See, network design is like chess.  The rules are pretty simple.  I explained them in my book Human Transit and I keep trying to improve on those explanations, here for example.  But doing it is hard, and you can spend years getting better at it.  So it helps to have someone at the table who has done it many times, who knows how to see the patterns of opportunity in your city’s geography, and who can explain why an idea works, or doesn’t.