Urban Transportation Redesign
How We Imagine Our Cities. Ours will always be a nation of cities, towns, and rural areas, and as we visualize America’s future, we want to have a positive vision for all three ways of living. Each way of living creates an economic, social, and environmental region. And in each kind of region, in each area of the country, we will want our grandchildren and their grandchildren to remember us fondly for having a spirited vision of how to live well in every region of our country.
The future of urbanized America is the puzzle to be examined here. A city is an economic and social engine of great power, if it works well, because it brings together in one relatively small area an enormous and diverse mix of talented people. The more talent, the more cross-fertilization; the more cross-fertilization, the more innovation; the more innovation, the more social energy. We want to imagine self-perpetuating success spirals taking root in all our cities. We want Americans at all income levels to feel at home where they live, with opportunities to pursue, careers to enjoy, professional growth to experience, families to raise, neighborhoods to love, and rich local cultures to appreciate.
All cities share the same core concept. A city is a crossroads for trade and talent. The more talent it brings together, the more cross-fertilization it creates. Cities thrive when they succeed in connecting people, resources, and markets.
This core principle of urban success rests on a city’s physical ability to help people move from place to place, easily and quickly, as opportunities present themselves. Cities benefit in a thousand ways from being smart about mobility. Because we want our cities to be thriving centers of human civilization, we also want our citizens to models of successful mobility. Not just for today, not just for tomorrow, but for centuries and centuries to come.
And this is where so many cities hit a wall. They have an aging script, and they apply it to everything. Build roads. Build side roads, build highways, build interstates. Tie residential areas together with roads, tie commercial areas together with roads, tie economic regions together with roads. And sell cars to everyone, as many as possible. It is America’s suburbanization script, and twice a day we set the script in motion. We pour the American workforce into its cars and dump all those cars onto the highway system, all at the same time. Then things break down. Drivers get caught in merciless congestion, and the twice-a-day commute stretches out and stretches out. Why has our script done this to us? The more we build out the suburbanization template, the worse our congestion seems to become.
Is it possible that something is amiss with our descriptive worldview and our directional worldview? Has our implicit success standard been hastily chosen? Has our civic competence fallen short?
We are up against it. Though we may imagine the city of the future as a treasure of human culture, in the real world of morning and evening commuting, we have encased ourselves in gridlock. Where is the triumph of human capital we think a great city is supposed to produce?
Gridlock Math
Let’s begin by rebuilding our worldview.
Cities handle two kinds of travel - commuter trips and non-commuter trips. Commuter trips create much the biggest problem. Five major variables set them apart:
Participation Percentage. So many residents participate in the daily commute. Much of the working age population is in the work force, and even those in school participate in portions of the commute.
Frequency. Commuters travel frequently, eight or ten times a week; more, if they hold two jobs.
Time Windows. Most commuters travel in narrow time windows – between six-thirty and nine in the morning, between three and six in the afternoon.
Travel Radius. In large metro areas, the travel distances from home to work and back again are long – ten miles, twenty miles, forty, even sixty.
Origin and Destination Patterns. Trips for morning commuters originate where people live and end at their places of work. The afternoon commute reverses the direction, but both ends of the commute involve “Many-to-Many” travel. People live almost everywhere and they work almost everywhere. Dad goes here, Mom goes there, and the kids go somewhere else.
The math is daunting. So many residents commute, in a many-to-many pattern. They do it twice a day, they aim for narrow time windows, and they often travel long distances. Twice daily these habits create huge surges in demand.
Let’s build on this line of thinking. Let’s imagine ourselves as the designated buyers of a transportation strategy for the city of tomorrow. We need a directional worldview that properly explains the challenges we will face; we need a proper success standard; we need a solution strategy that will work effectively for the city of tomorrow.
Let’s first define the sort of capacity that we are interested in creating. Travel behaviors generate demand; transportation suppliers are charged with creating supply. Just what is it that consumers demand? Just what is it that planners are expected to supply?
Let’s work the problem using lane-miles as our metric. And let’s start with demand. We begin with an individual car and the commuter who’s behind the wheel. A single car is approximately fifteen feet long. A defensive driver leaves a two second gap between her car and the car just ahead, and we will work the problem on this assumption, knowing in the back of our minds that the real world is populated with an abundance of tailgaters as well. At 30 MPH, a defensive driver requires a safety gap of nearly 100 feet. As a rule of thumb, therefore, let’s define 100 lane feet of highway as the amount of capacity a single motorist requires when traveling at 30 miles per hour.
How many motorists will it take to fill one lane mile of roadway to capacity? At 100 feet per motorist, our demand load can be penciled in as 50 motorists per lane mile. Yes, tailgating considerations let us squeeze more motorists into a single lane mile, but on the other hand, drivers like to go faster than thirty miles per hour, and when they do, 100 lane feet per motorist is not a bad ratio to use.
Next we modify this rule of thumb to accommodate rush hour realities. Some motorists start early, others aim for the middle of the rush hour, others are happy to bring up the rear. Instead of one wave of motorists using the roads and disappearing, we will posit three waves of motorists using the roads and then parking their cars. Now we can imagine ourselves accommodating 150 cars per lane mile, once our mental model assumes three waves of rush hour travelers, not just a single wave.
So far so good. Now our thinking moves in the other direction. As city highway systems fill up with motorists, everything slows down. A highway system that easily accommodated three waves of motorists in an earlier year is now hard-pressed to handle even two waves of motorists. We adjust our metric accordingly. A single lane-mile of capacity now accommodates only 100 motorists over the course of a whole rush hour.
Now we think long and we think large. In our mathematical imagination, we envision our entire metro area growing by a million people in coming decades, and we further expect half the new residents to be commuters driving their own cars. In other words, half a million new commuters on the roads. Let’s translate that into lane miles of demand.
500,000 new commuters, divided by 100 commuters per lane mile, equals what? Answer: 5,000 lane miles of new demand. That’s a challenge.
Now. What about new lane mile supply? Will we as transportation buyers have an easy time adding five thousand lane miles of new supply to the metro area we serve?
Not very likely. A metro area that grows by a million people will add quite a bit of highway capacity to its outer suburbs. Those highways will connect new homes to new strip malls. Mid-day shoppers will still be able to get around.
But the commuters are a different story. Only a portion of their commuting needs will be served by new highways built at the suburban edge. Much of the lane mile capacity they require must still be furnished by the metro area’s existing highway network. Let’s imagine, for the sake of argument, that 2,000 lane miles of new demand can be accommodated by new supply built at the suburban edge. Let’s also imagine that 3,000 lane miles of new demand can only be met if new lane miles are added to the pre-existing highway network.
Now we are up against the hard reality of metropolitan growth. Though population growth may take place primarily in the suburbs, much of the corresponding growth in commuter demand will be targeted at existing highways.
If half a million new commuters are to be given the highway capacity they need, by a system that’s already filled to the brim, planners should stand ready to add another two or three thousand miles of lane capacity. Where? To existing highways. Not too hard, right? Isn’t that why God invented bulldozers? So that highway builders can rip up sidewalks and storefronts and residential neighborhoods and use the bulldozed land for the creation of new highway lanes?
Well, no. On some highways, that’s exactly what we will do. Highways will be widened, selectively, to accommodate rising demand.
But the highway system as a whole won’t add nearly enough lane miles of new Supply to keep up with the urgency of new Demand.
More and more, America’s cities (and cities throughout the world) are finding themselves stuck. It is so much easier to add commuters and cars and lane miles of demand than it is to add lane miles of capacity. In many parts of every metro area, highway supply is frozen in place. The only feasible solution is to make rush hour last longer.
It is a painful remedy. As the demand for lane mile capacity rises, overall system performance declines.
In a smoothly rolling commute, motorists spend half an hour on the road, get where they’re heading, and leave the system. The load is moderate, the system flows smoothly, and everyone is happy.
When a metrowide highway system overloads, its behavior changes dramatically. As highways fill to capacity, traffic speeds slow considerably. Everyone stays in the system longer – a lot longer. Half an hour of commute time becomes an hour; an hour stretches to two. The number of motorists trying to use the system within the same time window expands, and expands some more. Everything drags out even further.
Rush-hour gridlock is the product of a self-intensifying feedback loop. As it slows, it fills; as it fills, it slows even further.
Why? By now we know. The passenger automobile requires at least fifty lane feet per motorist. That is an enormously expensive capital requirement. No city can keep ahead of the curve forever, and once its supply of highway lane miles falls behind, the ensuing downward spiral is almost unstoppable.
In a nutshell, that’s the problem. We can tuck it away in our descriptive worldview and refer to it whenever we like. But what about tomorrow? Does an effective solution exist, even conceptually? What vision of the future belongs in our directional worldview?
Possible Solution: The Virtual Commute
One feature of the modern commuting dilemma is almost surely permanent. A great many of us will always live at some distance from our jobs. And the “many to many” pattern will rule as well.
What about the virtual commute? Might that be the cure we seek? Instead of traveling to work physically, some of us might travel to work electronically. Sometimes we call this telecommuting; sometimes we call it telework.
We may have been hesitant about telework in the past, but now the momentum is growing. Company workforces have become global even as interactions among workers continue to be personal. Workers can interact globally from home offices as well as corporate offices. Work-at-home schedules allow employees to keep an eye on family demands that range from children’s schedules to elder care. Telework enjoys many advantages – environmental, economic, and life-style. When telework is incorporated into the normal business model, companies spend less money on office real estate and employees spend less time in their vehicles. Considerations of physical security and continuity of operations also support the case for workforce decentralization. Should an epidemic break loose, a heavy snow paralyze a city, or a terrorist incident take out crucial facilities, a decentralized workforce gets hurt less and recovers faster.
More and more one hears the maxim: “Work is what we do, not where we are.” Many kinds of work are indifferent to one’s physical presence in a particular workplace. One can research, write, audit, reconcile financial statements, provide advice, design machines, teach, or do medical diagnosis from almost anywhere, a market trend that surely plays into the StarbucksTM business model and the general success of the neighborhood coffee shop. As its logic ripples through the modern economy, telework will relieve cities of some of their commuter load.
Possible Solution: Fewer Lane Feet per Commuter
The car is a problem because it is such a hungry consumer of highway capacity. Fifty lane feet per car, a hundred lane feet per car, or even more at higher speeds. That’s a lot of asphalt per commuter.
Traffic engineers have always known this. Induce enough commuters to ride together and the demand for lane-feet of asphalt shrinks dramatically. Think buses, think light rail.
The City Bus Option. Bus systems can provide powerful solutions if the conditions are right.
Bus service works well in Singapore, an independent city-state of only 270 square miles. Its population of 4.6 million people gives it a density of 17,000 per square mile, just a bit more crowded than San Francisco on a territory roughly six times larger. One of the Asian Tigers, Singapore’s prosperity has created a broad middle class, just the sort of consumer population that usually owns one or two cars per family. Had Singapore allowed itself to become a city in which almost everyone commuted by car, its traffic congestion would now be intolerable.
Singapore is culturally different from America. Its Confucian value system honors the role of the strong and wise leader. This predisposes its public to accept a somewhat authoritarian style of leadership on many issues, including transportation. In Singapore, car ownership is tightly restricted. One must first acquire an ownership license, and like any restricted asset, such licenses will at times command a steep price. Only those consumers who possess ownership licenses are entitled to buy and operate automobiles, and in consequence, the number of cars on Singapore’s highway system is manageably small.
Singapore’s bus system fills the gap. Even during rush hours, bus service moves smoothly. With frequent service on all routes, Singapore’s bus commuters travel to their destinations much more quickly than bus riders in an equivalent American city.[i]
The lesson to be learned from Singapore is obvious: when bus service is frequent and unhindered by congestion, it works for everyone.
Curitiba, Brazil, is one of the world’s luckiest cities, blessed in recent years with mayors of great creativity. Curitiba is a city of 1.8 million, with a population density just under 11,000 per square mile.[ii] The city’s buses move swiftly, not because cars are restricted in number, but because the city has created dedicated traffic lanes for the sole use of its buses. Curitiba speeds its buses along by turning traffic lights green when buses approach.[iii] At each bus stop the city provides a loading platform; riders pay for the ride as they enter the platform, even before the bus arrives. When a bus arrives at the platform, its doors open, its new passengers board, its doors close, the bus is on its way.[iv] Everything is optimized to support the bus rider’s desire for a fast trip.
Curitiba’s insightful approach to bus service created an astonishing increase in ridership; over a two decade period, total ridership rose by a factor of fifty.[v] How did the city evolve such an effective template? Jaime Lerner, the mayor whose genius did so much to put Curitiba on the map, was by training an architect and urban planner. Lerner lived and breathed smart design. The success of the Curitiba bus system testifies both to Lerner’s creativity, and more broadly to the vital importance of good design in all areas of modern life.
Might America’s sprawling metropolitan cities reverse their congestion nightmares were they to create bus systems that emulate the design principles and the performance standards that Jaime Lerner pioneered? What if an American city were to optimize every facet of its bus system to reduce traveler delay? With fast payment, fast boarding, fast travel using dedicated lanes, limited waiting at intersections, short service intervals on every bus route? Surely a few American cities could make it work.
Curitiba, though, is but an individual city of 167 square miles. Many of America’s urban areas are much more extensive, and their commuter travel distances are correspondingly greater. Could a Curitiba-style bus system handle the demands of a much larger area? Perhaps. Or perhaps not.
The Light Rail Option. A sprawling metro area can take some of the pressure off its congested highways if it builds itself a light rail system. As an independent network, light rail escapes some of the intersection delays that slow the pace of bus travel. Light rail trains can make longer trips at faster speeds than buses. And rail travel has a panache all its own. What’s not to love?
Even with its undoubted appeal, light rail has important drawbacks.
Its stations are in-line stations rather than off-line stations. A light rail train stops repeatedly to discharge and board passengers. Those who don’t want off have to sit and wait, over and over again.
Light rail is inherently a few-to-few transit system. No metro area can afford to extend light rail connections to all its neighborhoods. Light rail is an appealing choice for those whose homes and businesses are served by nearby stations; for everyone else, it isn’t much of a choice at all.
And, of course, light rail is anything but light in weight or cost. Its capital infrastructure is immobile, heavy, and expensive. A light rail city will be a little better off than a cars-only city, but it isn’t really the fast, many-to-many answer that American cities require.
Possible Solution: Automated Guideway Transit
The Curitiba bus system was reverse engineered from a vision of excellence. Let’s try a similar reasoning process for an American metroplex. We begin with a success standard. Then we visualize a set of solutions that will create the success we want.
An excellent transportation system provides fast travel speed to every commuter. It delivers many-to-many connectivity, enabling commuters from anywhere in the metro area to reach destinations anywhere else in the metro area. Measured in lane feet per commuter, its ratios are low, its efficient use of capital admirably high. Wait times are short. The system is comfortable and stylish. It operates quietly. It carries a high enough percentage of the entire commuting population that auto loads on the highway system remain manageable. For those who drive, the killer rush hour is a thing of the past.
That’s the success standard, the vision we want to realize.
What’s the solution? What’s the design paradigm that meets our standard?
Let’s begin with an ambitious design hypothesis. Call it point-to-point automated guideway transit.[1]
Think lightweight vehicles, much smaller than light rail train cars, holding ten to twenty passengers at most. Think elevated single-lane guideways, twenty to thirty feet above street level. Think off-line stations, spaced every mile or mile-and-a-half. Think automated cars traveling non-stop from origin to destination. These are the essential design features of automated guideway transit.
When an automated guideway vehicle is to enter a station, it pulls off the main guideway and enters the station on a deceleration spur. First it unloads its arriving travelers, all of whom were bound for that specific station. Then it picks up a new group, all of whom are traveling to the same destination. With its new passengers comfortably seated, it pulls out of the station, gains speed on an acceleration spur, then merges onto the main guideway. It travels directly to its destination and discharges its passengers. There were no intermediate stops.
A proper guideway network blankets an entire metro area. A metro area of 400 square miles will require 150 to 300 stations. Guideways running north or south will be built thirty feet above street level, say, while guideways running east or west will be built twenty feet above the street. (Or perhaps the east-west guideways will be thirty feet up and the north-south guideways twenty feet up.) Each northbound guideway is paired with a corresponding southbound guideway, with a separation between them of a mile or a mile and a half. Eastbound and westbound guideways are paired in the same manner. At every intersection of two guideways, eastbound and northbound, say, there will be two exit-entrance guideways. One might carry vehicles off the eastbound guideway onto the northbound guideway. The other ramp will carry vehicles off the northbound guideway onto the eastbound guideway.
Let’s say Greg has to make a trip. He arrives at his station, selects his destination, and is directed by automatic signage to the platform where his car is to pick him up along with others traveling to the same destination. The vehicle resembles a stretch limo, with seating for at least ten but probably no more than twenty in all.
Greg’s vehicle scoots quickly through the guideway network – no intervening stops – and reaches its destination station much more rapidly than an automobile could. When Greg arrives, he walks the last few blocks, or takes a local jitney to his final destination.
This is the essence of the solution vision. And it meets the core success standard: Many to many service, fast, lightweight, favorable lane-feet/commuter ratios, lower capital costs per mile than light rail, not the least hamstrung by automotive congestion.
Let’s visualize the building blocks one would use to assemble such a system. Think safe, think modular, think lightweight, think stylish.
Everything begins with the passenger vehicle. Its wheels are rubber rather than steel so that its ride will be quiet rather than screamingly loud. Relative to the train cars used in light rail, it is shorter, narrower, lower, and lighter. The undercarriage picks up electric current from the guideway and uses electric motors to propel the vehicle. The undercarriage also uses what I think of as the “Ed Anderson design” to choose the guideway it wants when the vehicle comes to a Y. If the vehicle wants the right hand guideway, it raises its right side gripper arm and pulls itself onto the right hand guideway. If it wants the left guideway, it raises its left gripper arm and stays to the left.
For maintenance, the passenger cabins and undercarriages are modular and can be snapped apart, serviced in different shops, and then reunited. Modularity permits the upper and lower halves to be replaced on separate capital budgeting cycles.
The guideway system reflects a similar spirit of modularity and lightweight strength. At its base, it rests on sockets implanted in the ground. Each support pole plugs into a corresponding socket. Support poles rise twenty or thirty feet into the air and create the support system on which the actual guideways are mounted.
Consider the socket design and the ease of installation it provides. In phase one of guideway installation, street crews dig relatively modest holes, position sockets in those holes, and secure those sockets in place with concrete and rebar. As soon as the concrete dries, crew members cap the socket they just created and move to their next worksite. Socket by socket, the mounting system for an aerial guideway is set in place.
In phase two, crews drop the support poles into the sockets and secure them firmly.
In phase three, crews string aerial support systems from pole to pole. In phase four, crews drop the guideways themselves into place, fastening them to their aerial connectors. Each phase begins and ends quickly. Crews do their work and move on. Traffic on the highway below is never interrupted for very long.
As a useful byproduct, the tangle of phone lines and power lines that hang above so many city streets will be restrung, tucked into the superstructure of the guideway system. Now those lines disappear almost entirely from public view, a pleasing aesthetic bonus.
A guideway system that serves a metro area of 400 square miles might have 600 linear miles of guideway. Designers will want to test such a scenario for its potential carrying capacity. Assume conservatively that each passenger consumes ten linear feet of guideway. At ten lane feet per passenger, if you will, the system will carry 500 passengers per guideway mile, for a systemwide total of 300,000 passengers in all. Let’s assume thirty minute trips, on average, also a conservative estimate, which implies five full batches of commuters over the course of an entire rush hour.
Five batches times 300,000 commuters per batch. This suggests a potential carrying capacity of 1.5 million commuters, even under relatively conservative load assumptions. Not a bad outcome. Cut the estimate by a third, just to be safe. Imagine the rush hour impact of pulling one million motorists off the local highways. Everyone comes out ahead.
Think Ahead, Design Well, Live Better
What does this sort of reasoning process teach us about competent long-range civic thinking?
Descriptive Worldview. We learn to state the demand for highway capacity and the supply of highway capacity in lane-feet per motorist, and in motorists per lane-mile. And we discover that the demand for highway capacity – stated in total motorists and total new lane miles required – will eventually outstrip any metro area’s capacity to supply additional lane miles. Once demand outstrips supply, metro areas sink into congestion and eventual gridlock.
Directional Worldview. We learn to search for solutions that can handle far more commuters per lane-mile. There is promise in telework; there is promise in Curitiba-inspired bus service; there is promise in light rail. But none of those truly meets the fast, many-to-many commuting requirements of the modern urban population. We need something more.
Success Standard. A great commuting system gives fast, many-to-many service. It has very favorable commuter-per-lane-mile ratios.
Solution Vision. If we have direct, point-to-point service on an automated guideway system, we can get speed, many-to-many coverage, and favorable commuter-per-lane-mile ratios.
There is a discipline to far-sighted citizenship. The more we push ourselves to reach for greater competence, the more capable we become.
Steven Howard Johnson. 12.1 Version 2011-06-27.
[1] Personal disclosure. I own shares in Taxi 2000, a company that hopes to play in the automated guideway market of tomorrow. Its service model is somewhat different from the one I propose here. I inherited my shares from my late father; they represent far less than one percent of Taxi 2000’s total capitalization.
[i] Interview with David Summers, retired Foreign Service Officer, December 2005.
[ii] Wikipedia, October 27, 2010.
[iii] See VirtualTourist.com, “Best Public Transportation System in the World,” re Curitiba’s bus system.
[iv] Charles Landry. The Art of City-Making. Earthscan. 2007. P 379.
[v] Joseph Goodman, Melissa Laube, and Judith Schwenk. “Curitiba’s Bus System is Model for Rapid Transit.” Excerpted from a Federal Transportation Administration publication. http://www.urbanhabitat.org/node/344
