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polycentric linear city:

a Prototype for a Transit-based human settlement

PLC is a prototype for a polycentric corridor growth strategy developed strictly around a transit-based intermodal transportation network.  Highly interconnected within urban spaces, station areas provide such high levels of accessibility that the need for auto use and ownership in area around its nodes would largely be eliminated. It is not meant to be implemented in its actual form, rather provide a performance benchmark to guide its application to existing conditions/opportunities.  I will describe its major components, requirements and benefits.

 

Color

Name

Description

 

Mainline Transit

  Fully automated line-haul transit.

 

Feeder Transit

  APM and/or small-vehicle zero-emission guided busway (automated).

 

Jitney Feeder Transit

  Guideway-compatible zero-emission bus

 

Roads

  Highway and arterial roads.

 

Residential District

  Residential "oasis", medium/low density,  school, retail/services. Auto-free.

 

Key District

  Mostly retail and services, high-density. Auto-free.

 

Office District

  Mostly high-valued services, office, high density. Auto/transit transfer hub.

 

Hub District

  Off-line Intermodal facility, manufacturing, warehouse. 

BACKGROUND

Originally, cities came about to join people, to enhance their security, to favor the exchange of goods, information and emotions; to eventually expand their individual selves into a wider social conscience.
In recent decades, this web of relations has been dilated and lacerated by networks of highways and streets. By expanding and dispersing the  flow of people and goods, the vitality of local communities has been traded for increased regional mobility.
I believe that a transit-based transportation and land use revolution is mature and that it would largely contribute to the solution of  those problems; this will allow for the creation of striking and unprecedented new solutions to human settlements.. It is my belief these new corridor-based urban growth strategy will disproof many wrong assumptions about the inevitable deficiencies of social coexistence.
All over the world, the automobile has completely and pervasively reshaped the urban form, by conforming it to its needs. The unrelenting desire for the freedom, convenience and flexibility that the auto brings have largely overridden other concerns about the quality of urban  life. With no end in sight to the increase in car ownership and use, the accommodation of auto mobility directly requires an ever larger share of urban space and economic resources. Its high personal and public costs are degrading urban amenities, community quality, local accessibility, air quality, personal safety, social benefits, and therefore, sustainable regional land values and sustainable regional economic growth.
Regardless, its benefits are still perceived to justify these high costs. Through their daily choices and through political and ballot votes, urbanites confirm their readiness to pay the price because the total opportunity cost of known alternatives to auto-based development is much higher: perceived alternatives provide much less  freedom to participate in desired activities and , therefore, less personal freedom and economic opportunities.
A car allows me to go where I want, when I want; it allows me to choose among a great variety of providers of goods, services, employment and entertainment. As a business, it places me in close reach of potential employees, suppliers, clients and supporting businesses.
Reliance on transit, pedestrian and bicycle, instead, greatly limits this freedom of movement because of their short ranges, low speed, and/or limited destinations. Except for a few subway systems in very high density metros, they do not offer anywhere near the choice and speed offered by the auto.
In this paper I am going to challenge all these preconceptions as outdated and inappropriate by describing a new alternative.
In fact, recent advances in transit and information technology, the advent of intermodal planning, new land-use planning concepts and new evidence of successful non-auto urban forms around the world can be combined to create a prototype for an extremely efficient and equitable new urban form.

NEW TRANSIT TECHNOLOGIES

Many high density large metropolises in the world (Cervero, 1999) have extensive and intensive rapid transit networks, mainly underground, that act as primary and in some case the only mode of transportation for a majority of people living along their routes. In those cities, congestion and high parking costs so diminish the benefits of auto use that millions of people decides not to own one. These transit systems had to be combined through very dense neighborhoods because only a very high ridership could justify the operational costs of manual frequent service, and had to be kept underground or separated from buildings because of their noise, vibrations and structural requirements.
Recent advances in transit technology, however, suggest that transit could again determine urban growth, shape urban form and help create highly enjoyable urban environments. In particular, a number of implemented fully-automated transit technologies have proved the following:

  • Very high frequency of service, both peak and off-peak, without the high operation costs typically associated.

  • The ability to operate at very low levels of noise and vibrations, both internal and external.

  • The ability to perform safely and efficiently in fully automated control and operation.

  • Ability to effectively operate small vehicles and single-vehicle trains.

  • Extremely good safety records.

  • Cost efficient use of non-polluting and silent propulsion technologies.

  • Comparatively low capital and operational costs.

Fully automated small transit vehicles can operate at frequencies of up to 60 vehicles/hour without the typical high labor and energy costs associated with manually operated systems (labor generally accounts for 80% of operating costs). These frequency levels would allow for very high accessibility even for medium density areas.
Extremely low levels of noise and vibration permit the integration of transit stations and transfer platforms within building structures, with the potential of dramatically increasing the accessibility to land adjacent uses and facilitating transfers to other surface transit systems. Also, guideways can be built above ground and in proximity of most land uses.
Single small-vehicle trains are much lighter than typical multiple large-vehicle trains allowing for cheaper and smaller guideway structures.

Description of Polycentric linear city

I will here describe PLC as a prototype of an evolving  urban form as it would appear at  a specific stage of maturity.
In PLC, land uses types and intensities are strategically distributed around hierarchical transit/intermodal nodes to create clustering districts of development, a very efficient use of transportation infrastructure and comparatively extensive and  inexpensive access to desired activities. This creates opportunities for highly connected communities strongly focused around a compact nodes. This nodes  integrate public space, transportation hub and green areas.
The transportation system will consist of a highly coordinated intermodal network that walking, bicycling, rental-auto, owned-auto, rail, e-vehicles, air and truck modes, through the structural skeleton of its mainline and feeder transit modes.
The relationship, relative importance and hierarchical order of modes would vary widely in space. All intermodal combinations can possibly be chosen by a user from any location; however, their relative convenience will greatly vary depending on the location of origin and destinations of his trip/tour respect to transit node.
As shown in the chart below, the modal split associated with a location along the corridor would therefore be highly related to its distance from the transit nodes.

Essential to the viability of the prototype is the definition of very extensive auto-access and parking restrictions within the core areas of certain districts (key and residential nodes) and the provision of highly spatially integrated park-and-ride facilities at other stations (office nodes).

residential District Characteristics

Distance from station (feet)

0-200

200-400

400-600

600-800

800-1400

Auto access

No

no

no-restr.

restricted

Yes

Adjacent Parking/HH

0

0

0-0.2

0-0.8

1.0

Residential Density(DU/acre)

45-90

35-60

20-45

15-30

10-25

 

 These special districts are defined with precise sizes and characteristics for the sake of explanation. In an actual implementation, sizes and characteristics of each district type would vary according to existing topology, nodes service levels street patterns and developments. Also, these districts do not define continuous self-contained units, as much as defining the gradual tapering of essential characteristics with distance from transit nodes. They could be considered as a sort of contour lines of urban characteristics:

Following is a chart describing approximate average values for main land use components of  PLC:

District types

Area

Population

Res. Units

Res.Density

Workers

Jobs

acres

#

#

DU / acres

#

#

Key District

83

2400

1600

20

960

3700

Office District

25

600

400

16

240

3200

Res. District

38

5000

1700

44

2000

300

 

CRITERIA FOR PROTOTYPE IMPLEMENTATIONS

This corridor growth strategy can be overlaid over existing metropolises or cities of over one million in a variety of ways to accommodate, stimulate or direct  regional growth:

  • As a linear development linking opposite sub-centers through the CBD.

  • As a radial corridor development strategy through existing auto-based developments

  • As an overlay on existing transit corridor

  • As a new transit beltway linking major sub-centers.

  • As a comprehensive new corridor development plan through mainly greenfield sites.

  • As a combination of any of the above.

key regional factors

A extensive review of successful "transit-friendly" human settlements around the world has revealed one common characteristic: land constraints. Either by topography or by governmental policy. all those regions had or have severe limitation to the availability of cheap developable land.
Also, crucial is the location of the corridor and its nodes respect to existing and future major regional destinations, transportation hubs, employment centers.
For these reasons, we are going to assume that the nodes of the mainline system connect existing major sub-centers (malls and office parks), the CBD, a high volume inter-regional and commuter rail station, a major truck freight loading facility, and maybe ends at a major international airport. Especially the end of lines should be high volume destinations, such as an airport or a downtown.
The environmental impact of the mainline guideway should be minimized by aligning along freeways, existing or abandoned rail ROW, or low-density developments.
Selection factors would include the following:

n         Existing clusters of commercial and service activities at Key Node sites, especially at ends of lines.

n         High projected demographic growth in the region and/or potential for growth within study area.

n         Mostly low and middle income residents, preferably immigrants with inclination toward public space and mass transport.

n         Linearity of existing natural geographic boundaries and/or existing regional development (such as along the coast of South Florida).

n         High Regional Land Values and/or scarcity of developable land.

n         Flat or highly mountainous site area to maximize respectively bicycling or transit.

n         Proximity or adjacency to valuable environmental features (such as park space, seacoast, riverside, etc.).

n         Existing and available rights-of way segments: operating rail, abandoned rail, and highway.

n         Proximity of office nodes to highway exits and interchanges.

n         Existence, within 0.5-1 mile from the alignment of medium or high-density residential developments or large green-field sites.

 

PLC TRANSIT TECHNOLOGY


PLC PERFORMANCE REQUIREMENTS

Extremely high quality transit systems, and a high spatial and temporal integration and coordination between transit, walking, bicycling, E-vehicles, auto and freight are essential to the success of the strategy. Both mainline and feeder service should score very high in the following performance measures to provide the accessibility, comfort and convenience needed to outpace the automobile:

  • Frequency of Service

  • Visual Impact

  • Efficiency of transfers

  • Ride comfort

  • Noise & Vibration

  • Average Loading Time

Frequency of Service: Usually measured in vehicles/trains per hour. It has traditionally been restrained by available capital and operating financial resources, as well as by system engineering limitations. Today, those restrains have been largely overcome. Major factors are: system labor intensity, marginal cost per additional vehicle/mile, minimum size of vehicles in the fleet, minimum safety delay between trains (0.10-6 min.), minimum vehicle stand-by time (20-90 seconds), minimum train size (1-4 cars per train),
Using small vehicles/trains, a  number of urban scale automated systems around the world operate at frequencies of 30-60 trains/hr in low and medium density areas.
            plc-Mainline: Full automation allows the mainline system to perform at 60 trains/hr during peak hour and 20-45 t/hr during off-peak and night periods. Minimum train size is one small vehicles (30-50 pp.). Approximate stand-by time is 15-30 seconds. Minimum safety delay can easily be set at 60-80 seconds, but it could be further reduced when improved accessibility justifies the extra costs of better controls.
            plc-Feeder: Whether it is automated or manual, fully grade-separated or with mixed-grade sections, it has to be of very high quality and frequency, and be extensively upgradeable in service level. In tha case of initial manual operation, the frequency would initially be restricted by labor costs; the latter should be heavily cross-subsidized until automation is incorporated to spur real estate development.
Efficiency of Transfers: It defines the amount of time needed to transfer from one mode to the other. It is especially important in a transportation network where a large number of trips involve multiple modes, since transfer waiting-time is generally perceived by travelers as 2-3 times longer than actual travel time. Major factors affecting efficiency of transfer between two modes are frequency of modes, schedule synchronization, intermodal facility design and traveler information.
            PLC: Scheduling of mainline and feeder service are synchronized according to real-time vehicle location information and remote traffic light control to achieve temporal coordination. Intermodal transfer facilities should be integrated in a single 3d dimensional structure within a major activity center. Improved frequency of both feeder and mainline greatly hugely decreases typical transfer time.

Ride Comfort: A transit ride can be more or less enjoyable. Important factors are: vehicle design, strength and smoothness of acceleration/braking, internal noise, internal vibrations, crowding level, seating vs. standing capacity, exterior views, vehicle amenities, cleanliness, air quality, lighting.

                plc-Mainline: automated propulsion controls allow for smoother acceleration and deceleration. Mostly elevated and at-grade routing provides opportunities for pleasurable exterior views and direct integration into valuable land developments. Interior and exterior design and lighting will be carefully designed. A relatively small additional investment in vehicle design and amenities could provide a high return in terms of a pleasurable ride.

                plc-Feeder: A number of current APM technologies have proven smooth acceleration/braking and very low noise levels, because of no gear switching. Engine would produce no noise (Trans21, 1999). In mixed-grade systems, new low-floor design eases boarding increases traffic maneuverability. Given that feeder routes would be assigned permanently, their street surfaces should be carefully re-paved to provide for a smooth ride. Extensive use of traffic preemption/prioritization avoids stops at traffic light and largely limits queuing in traffic.

 Noise and Vibration Levels: The resulting discomfort a matter of intensity and frequency of noise, as well as quality; in fact, certain sounds and sound patterns are perceived as more or less annoying based of their quality as well. As far as noise intensity, it can vary among transit systems from near silence (0-10dB) for Low-Speed maglev and rubber-tired linear induction systems, up to noisy (60-70dB) for diesel bus and old steel-wheel commuter rail. New steel or alloy wheels are much quieter, especially at low speeds and curvature levels, which are typical in proximity of station areas.At medium and low speeds, noise of the system is a function of suspension/guidance interaction, vehicle engineering, propulsion and AC noise, guideway insulation and structural separation.

Vehicle Loading Speed: It is a function of floor level, doors size, vehicle stand-by time, eventual ticketing interface. It can vary between 15-90 seconds. Both small train size and high frequency have great effect in reducing loading speed. Small trains with means less passengers that could somehow delay dwell-time; high frequency means that missing a train would not be a be deal. (See how guideway can integrate into entertainment and retail development in Buenos Aires "Le Rosedal")
Visual Impact: It is a function of vehicle size and design, station design, guideway size and design, level of visibility of guideway, frequency of service, level of spatial integration within existing developments.

.....

selection of TRANSIT TECHNOLOGIES


Mainline System

Given the identified need for very frequent service at all times of day the choice falls on some kind of automated guideway system with small and medium size trains.
Automation controls have recently been applied to a number of previously manually operated systems, and currently in San Francisco's BART.
......Larry data .....urban scale AGT.......Several implemented systems around the world comply with a number of these performance measures. Therefore, an analysis of those existing systems and the current developments of their manufacturers should give us an idea about the feasibility, expected costs and actual performance of such system.

Those systems are:

  • Meteor Subway Line. Paris, France.
  • Vancouver Skytrain. Vancouver, CA.
  • VAL AGT system. Lille, France.

(See attached data charts on some AGT systems by Dr. Fang Zhao at FIU).

Feeder System

High frequency  at peak and off-peak periods is even more critical to a successful feeder system. Operating speed and frequency of the feeder system should approach the levels of the mainline system. In fact, on average, PLC residents' daily tours would involve more feeder system trips than mainline ones; therefore, its frequency should be even higher than mainline. To support the costs of a very frequent and fast automated feeder system, the land around its stations should concurrently and very extensively be developed or re-developed. I have identified two transit modes that could satisfy this performance requirements: 

     1.Evolving Automated Guided Bus: Given the necessary phasing in the development of large transit-oriented development around stations, an "evolving" transportation mode would allow for the efficiency of transit to grow with the size and type of the real estate developments.
While frequency is maintained relatively high throughout development stages, an initial manually operated mode is progressively transformed in a driver-less grade-separated system integrated with new real estate developments.
A large fleet of  low-floor non-polluting small size buses (electric, fuel cell or hybrid) would operate on mixed-grade at a very high frequency. It would incorporate a combination of signal preemption, remote prioritization and remote vehicle location technologies to provide a frequent and highly synchronized feeding service to the mainline AGT system.  Initially, the frequency of the service would be greatly limited by the manual operating costs. Relatively high frequency should be cross-subsidized even during this initial phase to create the conditions for district development.
All feeder buses, as in Adelaide, should have built-in special guiding lateral wheels and electric controls.
Guided Busways are currently operating in Adelaide, Australia, (see Fig. 5a & 5b)and  Fukuoka, Japan, and currently under development in Paris, France.

01.jpg (95600 bytes)

Figure 5: From top, PLC adaptation to topography; Guided busway as implemented by Daimler-Benz in Adelaide, Australia.

The choice of guided-busway technology allows for the operation of the same vehicle in driver-less mode on separated-ROW, as well as manual control on mixed-ROW; therefore, some feeder vehicles could be manually operated at lower frequencies through auto-based neighborhood, then switch to automated controls as it enters the Office node and Continue to the Key node.(...image...)
In fact, The system in Adelaide is currently manually operated, though it is "predisposed" for control automation
The non-polluting technology, among other benefits, would allow the critical spatial integration of the feeder system, mainline system and real estate developments.
This system should be developed in such a way that future grade-separation and control automation could be implemented at a later stage, when increasing building densities of feeder nodes would justify the integration of a new guideway to improve speed and frequency. Developments should reserve space for future guideway
The short range of the batteries would no t be an issue because routes are very short; battery could be periodically replaced at key district stations.
Fuel-cell buses are currently operating in a number of cities including Vancouver and Los Angeles. Diesel-electric hybrid propulsion buses are currently operating in Seattle.
To allow for tighter integration within building structures, mechanical guiding wheels could be installed to permit operation in very small guideways or tunnels. This would also facilitate future automation of the system.
Electric battery-powered low-floor mini-buses are currently operating in many European cities, including Rome.
Mainline and feeder systems should be highly integrated in space and time. The temporal integration would be achieved through high frequency of service, real-time schedule coordination. Spatial integration is assured by the design of intermodal exchange facilities that minimize transfer time.

    1.Automated People Mover (APM): 

 

........

 

 

 

Freight within plc

Freight handling for residents and companies in auto-free areas of the corridor would also be integrated in the transit system. 

It would serve these areas in 2 main ways:

         Items would arrive through truck at office nodes; or through railroad and air at key nodes; then it would be dispatched through the mainline and feeder systems on specially equipped vehicles along with passenger train sets. Items would then be debarked at the station closest to its destination and delivered through small electric vehicles to the final destination.

         Items would arrive through truck at an "offline Industrial stations" placed in between Key stations of the mainline system; then, either delivered to their final destination in residential, key or office districts through small e-vehicles or loaded on mainline vehicles for delivery to key nodes.

Economies of scale are going to be essential for this service to be implemented profitably by public or private companies. Key and residential districts with a few thousands employees and/or residents should support at least one full-time freight handler. priority mail and freight,
Except for high priority mail, most freight would utilize excess transit system capacity in night and off-peak periods. It is conceivable that the a number of  vehicles be used for passenger during the day and for light freight at night. 

Spatial-Temporal Integration

Essential to the success of the strategy are high spatial/temporal integration and coordination between the two transit modes and all other modes. In economic jargon, the personal utility of being in a place varies enormously through time; therefore the integration should strictly be spatial/temporal.

Spatial integration

A very high spatial integration of mainline system, feeder system and station area developments is essential to reinforce the benefits of high temporal integration.
All three elements should be integrated spatially, visually and functionally to maximize the accessibility of station area activities by residents and transit riders. Bicycle storage/lockers/rental facilities should be available at many stations, especially if weather,  topography and local culture are favorable to bicycling. For bicycle rental, regular stored-value transit passes would be used; the rental-bicycle value would be temporarily charged to the card and refunded at the return location. Rentals might include new electric-bicycles. Many similar systems are in use in Japan and northern Europe. Daily and hourly auto and station-car rental should be offered at  most office districts' parking structures. These would allow PLC residents to conveniently access auto-based developments, their services, and to enjoy weekend rides.

teMPORAL INtegration

Temporal integration, essential to feeder and mainline modes, is achieved through high frequency, high maximum speed, remote vehicle location, remote management of traffic light preemption/prioritization (for mixed-grade feeder), real-time schedule coordination. These technologies are rapidly becoming cheaper and more powerful.
A remote control center elaborates real-time information on the position of each transit vehicle, compares it to the optimal on-schedule position, and accordingly control the synchronization of lights at intersections. The control center can, therefore, adjust traffic lights phasing and communicate desired speed adjustments to drivers or in-vehicle controls, to make up for any delays.
Each of these technologies is currently implemented in several European and American cities.
Also, given the short length (0.5-1 mile) of mix-grade feeder system routes, any delay would hardly accumulate to become significant.
Essential to the temporal integration is, again, frequency;  for the mainline it is both feasible and cost effective because of control automation (see data on ................Vancouver Skytrain).
For the feeder system, instead, a high frequency would mean fairly high labor and operation costs because of manual operation (at list during the first phase).
In both cases, the cost effectiveness of high frequency service is highly dependent on the density and type of land developments that are within station areas. The latter should create a demand for service that is strong di-directional demand throughout  the day, and therefore make the best use of transportation infrastructure and staff.

Financing & Implementation

Please, refer to the following proposal for a New Jersey Linear City, or a highly integrated transport/real-estate development running east-west through Midtown Manhattan: http://www.linearcity.org/rufo/nj-plc06.htm.

The plan is shaped around a transit-based intermodal transportation network that would utilize existing highway rights-of-way and rail tracks, as well as new tunneling to link Morris-Essex commuter rail to most NYC subway lines, Grand Central Station and the planned 2nd Avenue subway.

 

The realization of such an ambitious and broad plan surely requires an elaborate and complex public-private financing and decisional organizational structure. However, cities and metropolises have realized highly successful transit-based human settlements through very different, and even contradictory, public-private organizational structures (Cervero,99).
For example, in Tokyo great conglomerates have been given freedom of building extensive transit-based developments on their own, whereas in Zurich similar success has been achieved through numerous incremental ballot box votes.
Regional institutions would be ideal at coordinating the plan; however, that can also be realized by State or Local. Consortiums of developers, Real Estate Investment Trusts and Public-Private Joint development agencies could be major players.
I

LEGAL ISSUES

Please, refer to the following document on legal issues involving large-scale corridor-wide transit-oriented developements: http://www.linearcity.org/rufo/Lyna-final01.htm.

Phasing & Construction

The high interdependency of mainline system, feeder system and real estate developments require that the phasing be somewhat concurrent. Both transit and real-estate infrastructure of the plan should be developed as extensively as possible given market demand; only this would quickly achieve the critical mass of transport and development that will start multiplying returns and drive further developments. Initial transportation and real estate development should be in balance between self-sustenance and flexibility for  future expansion.
Substantial guarantees on construction times, especially concerning transit infrastructure, are going to be essential for all private players involved, and would highly affect their willingness to participate.
Critical Mass is going the most important factor of success. Only a fast, efficient and extensive network will bring real estate development. Only intensive developments at some nodes will bring other developments at other nodes. Only high density around nodes will bring the ridership levels that would justify the costs of a super-high quality transit network.

Selected Bibliography

         Ben-Akiva, Moshe and Bowman L. John.  Activity Based Travel Forecasting.Activity-based Travel Forecasting Conference.Wash., DC: DOT.

         Ben-Akiva, Moshe and Bowman L. John. The day activity Schedule approach to travel demand analysis. Wash., DC: TRB annual meeting 1998.

        Bhat R.C., and F.S. Koppelmann. A retrospective and Prospective Survey of Time-use Research. Northwestern University. (#990830).

         Bhat R.C., J.P. Carini and R. Misra. On modeling the Generation and Organization of Household Activity Stops. TRB Annual Meeting, 1999.

         Cervero, Robert. The Transit Metropolis. Washington, DC: Island Press, 1998.

         Shen D., Huang J. and Zhao Fang. Automated People Mover Applications: a worldwide review. Washington, DC. : National Urban Transit Institute.

         Warren, Roxanne. The urban oasis. McGraw Hill, 1997

        Miller, J. Harvey. Measuring space-time accessibility benefits within transportation networks: basic theory and computational procedures. Geographical Analysis, April 1999.

        Zhang M., Q. Shen and J. Susssman. Strategies to improve job accessibility- a case study of Tren Urbano in San Juan Metropolitan Region. 1998.

        Niles J. and D. Nelson. Measuring the success of Transit-oriented Development: retail market dynamics and other key determinants. APA National Planning Conference, 1999.

         Chang-Ing Hsu and Shwu-Ping Guo. Residential location choice in a n urban area with surface streets and rail transit lines. TRB Annual Meeting, 1999.