URBAN MOBILITY IN THE 21st CENTURY

Presented at the Electric Vehicle Symposium, Brussels, 1998

Abstract

As a means to eliminate freeway congestion and minimize pollution at once, the most numerous personal vehicle in the 21st century will eventually be a two/four-passenger freeway-capable microcar. At 2.5 meters length and a curb weight of 350 kg, the occupied microcar can be efficiently transported for urban transits in excess of 10 km. The transit concept is known as Dual Mode, so-named because the car can be moved about in two ways: 1) driver-operated for local mobility, then 2) transported on a dedicated guideway for the longer commute. A single-lane of the freeway, converted for transporting microcars, provides the car throughput equivalent to 20 lanes of conventional cars.

Such a mass transit system will be fiscally self-supporting, because it supplants the futile theme of transit administrators to "get people out of their cars" with "get cars off the road and onto transit".

In Dual Mode, the limited-range issue of the EV becomes essentially irrelevant, because most long-range travel is done aboard the transporter. The small EV and Dual Mode are thus synergistic companions, each making the other more feasible. If purchase of a Dual Mode-compatible EV is associated with relaxed congestion-free travel, a consumer-driven market will outstrip the modest goals of Clean Air legislation throughout the world.

Urban Transit Evolution

Public mass transit, from horse-drawn carriages-both wooden wheel to flanged rail-eventually evolved to the electric streetcar, first introduced in the USA in Richmond, Virginia in 1888. Development of the ICE/ICV in Germany (1885-6), followed by the pneumatic tire, has produced the most versatile of all methods of urban conveyance: the car/highway system. The freeway (1930's), with over/underpasses and enter/exit ramps, has further improved urban mobility.

Rail

Over the fifty years between 1890 and 1940, the railed streetcar and subway were the predominant means of urban mass transit. Beginning in the 1940's, rubber-tired trackless trolleys and diesel buses gradually replaced the steel-railed vehicle in many cities. Steel-railed transit systems, installed over the past fifty years in the USA, have been notably unsuccessful in fulfilling the transit needs of the modern low-density distributed city. Actual riderships are far below projections, requiring heavy subsidy by the taxpayer.

Bus

The automatically steered German O-Bahn electric bus on an elevated guideway is another example of a successful conversion from rail to a road-like guideway. The O-Bahn type has a unique feature: the capability to leave the guideway-whether elevated, tunneled, or at-grade- to travel on conventional roadways. This flexibility allows the bus to travel on conventional at-grade arterial roadways through districts and neighborhoods that are not amenable to fixed-guideway transit systems. By avoiding at-grade congestion while retaining the flexibility of the bus, the O-Bahn can improve accessibility. But the SOV continues to be the favored means of urban travel.

Maglev

The smoothness and quiet of maglev at urban speeds provides an environment similar to a private office, except for the moving scenery. Since there are no moving parts in the running gear, reliability and maintainability are enhanced. The Japanese HSST-200 was designed for the urban application, having onboard propulsion coils, this feature providing individual speed control, as required for short headway's. The Japanese Ministry of Transport certified the HSST for commercial application in 1993. Failure modes have been tested for safety and operational recovery. Derailment or toppling is impossible due to the guideway wrap-around construction of the under-carriage. Also, the attraction type levitation method precludes concern about magnetic fields near passengers.

Congestion

In the modern low-density city—typical in the USA--only 3% of commuters use public transit. This is because the car/highway system over the past seventy years has shifted concentration of homes, workplaces, and shops from within walking distance of mass transit rail/bus stops to lower density suburbia. Such distributed development is not compatible with conventional mass transit. Stated more simply, people who want to use public transit must first get to the rail/bus station from their homes, then get from the station to their destinations. To walk the usual 1-10 kilometers distance to/from the stations is quite impractical for most commuters. As a result, 13 out of 14 commuters in the USA drive alone, giving rise to the term "SOV" (single occupant vehicle).

Mass production techniques have made the personal car affordable to almost every citizen. In the USA, there are now 1.08 cars per licensed driver, with many owning vehicles designed for specific purposes: vans/sport utility vehicles, pickup trucks, sport cars, and motorcycles. We have now built a society based on the car/highway system from which there is no turning back.

Car pooling is near impossible, because few commuters can readily find a nearby neighbor who works at the same plant, on the same shift, and doesn't have personal requirements to stop by the child care center or buy groceries for dinner. High Occupancy Vehicle (HOV) lanes in the USA, intended to coerce SOV commuters into car-pooling, have failed to mitigate congestion. This necessary dependence on the SOV results is massive congestion on urban freeways and intra-city arterial roads.

Current Electric Vehicle Designs

Most EV designs today are attempts to duplicate the payload and speed capabilities of conventional ICV's, including a desire to approach the range of the ICV. The resulting designs—particularly those employing lead-acid batteries—produce an imbalanced design, with battery weight often approaching 45% of the curb weight, such vehicles sometimes referred to as "lead sleds". The disproportionate weight of the battery requires increased chassis weight, further compounding the design imbalance.

Polls have revealed that few commuters need a daily range in excess of 70-km. However, the inconvenience of a refueling stop perpetuates the desire to have the 500-km range of a typical ICV, with an average once/week refuel requirement. Since the EV can be automatically recharged every night, vehicle range requirements between 'refueling' stops are obviously much reduced. EV design practice that does not recognize this difference is likely a product of the rote that ICV designers can be subject to when trying to convert to EV.

Dual Mode

Dual Mode is so named because the car can be moved about in two ways: driver-operated for local mobility, then transported on a dedicated guideway for the longer commute. There are two types of carriage for the transported mode:

1) An individual car is either driven onto a guideway located beneath the car, or suspended from an overhead guideway, sometimes powered by an auxiliary motor. This type is a form of Personal Rapid Transit (PRT), but has the advantage of all Dual Mode systems because it provides self-transport to/from the guideway, usually several kilometers distant.

2) Many cars are clustered onto a transporter, sometimes referred to as a car ferry. The generic term for this form of Dual Mode is Vehicle Mass Transit System (VMTS). The transporter may operate on a dedicated guideway (steel-railed, rubber-tired busway, or maglev). The rubber-tired truck version can also operate mixed with conventional traffic on an arterial or freeway.

The VMT system (type #2) was selected for the "ultimate" design for the 21st Century City because it has the highest cars/hour throughput, lowest energy consumption, and can accommodate car designs without the encumbrance of special guideway attachment fixtures. It also is most compatible with the smooth and quiet maglev transporter. A dedicated (barriered) at-grade guideway, overlaid on the inside-lane of existing freeways, was chosen to minimize the high costs and obtrusiveness of the elevated guideway.

Transit in the 21st Century

Shortly after the turn of the century, the microcar--purpose-built for commuting and local errands--will replace the conventional ICV for daily use, the latter now consuming inordinate road and parking lot space. Many families will still retain (or rent) an ICV van/sedan for long-range family trips, camping outings, and heavy hauls. But they will become 'dust catchers', due to their infrequent use.

Dual Mode will have a profound impact on urban travel in particular, and quality of life in general. In 7-20 years, the microcar will become the most popular car in the industrialized world, reducing the wasteful use of the conventional-sized ICV for SOV commuting. A typical family with two working parents and a college student will own a seldom used ICE minivan, with three EV microcars angle-parked within the second garage stall. Freeway congestion will be virtually eliminated. Up to 80% of workplace and shopping mall parking lots will be redesigned, near tripling capacity. Human energy and time, now wasted in freeway traffic, will be available for more productive use.

The ultimate mass transit carriage for the 21st century City of the Future is maglev. Dual Mode based on maglev will make it practical for people to live up to a 150 km. from work and actually enjoy the commute. Extensions of an urban-based system will lead to an intra/intercity-compatible guideway network that will promote low-density growth into the hinterland, interspersed with an abundance of parks, playgrounds, small farms, and game preserves.

The currently pessimistic 3% market share of the EV circa 2007 will be trivialized by the newfound urban mobility availed by Dual Mode. Air pollution levels and global warming due to cars will drop far below that presently predicted by those who assume such slow acceptance of the EV.

Dual Mode Microcar

The transported mode for Dual Mode will be 'quality time' because the commuter can relax in a vibration-free and near-silent environment, watch TV, do office work including use of the cell-phone, work the Internet, take a nap, listen to stereo, or eat a packaged breakfast.

The minimum size microcar was selected to be 2.5 meters long--to match the typical width of a transporter for transverse unload/load—and 1.25 meters wide--to accommodate up to four passengers. However, a two-passenger microcar as short as 1.75 meters is possible, such a design maximizing the number of microcars that can be transported in the two-abreast forward-facing arrangement (above).

The Nissan Hypermini, the French Tulip, and the Swiss Horlacher City Car are typical of an emerging class of EV that fit the Dual Mode VMT system).

2 - Passenger Model

The driver is located closer to center than typical so as to improve lateral balance in the usual SOV loading. The drivers seat is equivalent in comfort/space to a business-class seat in a commercial airplane. The passenger seat is of adequate size, but not as sumptuous as the driver's seat. A fold-down worktable is attached to the lower edge of the right-side dashboard, below the multi-purpose TV/monitor/navigation display. A leaky coax on the guideway aids TV/FM use.

Although power-steering and power-brakes are not required in early designs, these features will be required in more sophisticated versions of Dual Mode so as to accommodate automatic steering and braking for rapid 'hands off' autoload and staging/clustering of microcars on the station loading platforms and on/off ramps.

Since knees are narrower than shoulders, the right-side passenger seat is located 700 mm aft of the driver's seat. This staggered arrangement allows the driver to readily enter/exit on either side. A jumpseat for a small child or baby carseat is located to the left of the passenger seat, this space also useful for groceries and similar small items.

Three Passenger Model (not shown)

The driver is placed in the center for two reasons: 1) to improve lateral balance, and 2) to create legroom on both sides of the driver for the two rear passengers. This center location for the driver is desirable for such a lightweight vehicle because the driver's weight can approach 30% of the gross weight. The rear seats are smaller, as in the four-passenger model, but oriented splayed 10 degrees.

Four Passenger Model

A conventional side-by-side seating arrangement can be accommodated at the density of coach-class seating in a commercial airplane: 105 cm from the outer edge of the driver's left-side armrest to the outer edge of the passenger's right-side armrest, and at a fore-aft pitch of 85 cm. The aft seat space serves as a small trunk with less than four occupants.

The 2-passenger model is designed primarily as a purpose-built car for SOV commuting and neighborhood errands—what some might think of as a 'second car'. However, families consisting of more than two people and living in apartments or high-density areas may not afford the cost or parking space of owning a microcar for each licensed driver and a standard-size car for the family.

The four-passenger model might better fit their needs.

The dilemma of which car to buy could also be solved by a growth in local auto rentals. Automation will permit reservation via phone keypad, followed by dispensing of a minivan or truck adjacent to the microcar as the renter drives into the neighborhood rental lot. Turnaround could be done in a minute.

Construction

An integrated design matched to Dual Mode favors composite materials and the associated fabrication technique. This is necessary in order to achieve a high strength/weight ratio, for two reasons:

1. Minimize the critical battery energy requirement for the microcar in its driven mode, and

2. Ease the design requirements for the transporter, especially the maglev type. The EV microcar proposed herein can be so achieved at 350 kg. curb weight. The design methodology being emphasized in the US Program for a New Generation of Vehicles (PNGV) has demonstrated feasibility of similar ultra-light car designs.

Crash Safety

Concern for personal safety, when contemplating a crash with a conventional-sized car, is an issue that will yield to public education. When the microcar becomes the most common passenger vehicle on the road, the mass difference in a crash is statistically lessened. Also, most high-speed urban travel in the 21st century will occur while the microcar is aboard the transporter, thus Dual Mode should result in fewer traffic fatalities than with conventional driving. Since kinetic energy is proportional to mass times velocity squared, the energy dissipated in a crash between two microcars will typically be about 15% of what is involved between today's conventional ICV's.

The aforementioned composites will also provide a high stiffness to mass ratio (like a Ping-Pong ball). Also, hi-tech crushable materials within the cab have proven effective in tests, and would be an integral part of the design. The Swiss Horlacher City Car, similar to the microcar, has also passed US crash tests when equipped with airbags.

Power Components

A nickel-metal-hydride or lithium-ion battery was sized at 80 kg. for this feasibility design. A 24-hp motor is required to achieve the design speed of 100 km/h. Computer-controlled charging is done during the garaged/parked condition, this arrangement making possible pre-heating or cooling the cab just prior to occupancy. If the charger fitting is located just above the front bumper, the charger is automatically engaged by simply driving into the fixed installation within a garage or parking lot. An alternate location for the charger fitting is underneath the floor, so to integrate it with the hold-down fixture that grabs the microcar during its transit mode aboard the transporter. This fixture would complete the magnetic circuit for onboard charging, thus topping off the microcars battery charge during transit.

Another 'charging' concept that is worthy of consideration is to devise an outright battery swap at so-called filling stations. A clever mechanical designer could automate such an exchange in seconds, much less time than a typical ICV refueling stop. Of course, automation of the ICV refuel stop is also possible. But the point to be made is that the battery swap concept can help allay the range concern.

Two Lanes for One

A side benefit of designing a narrow microcar to enhance the efficiency of Dual Mode is that a single lane could accommodate two lanes of microcars. For example, a typical 3.6 meter wide freeway lane would allow parallel microcars at a separation of 600 mm (two feet)—a bit tight at 100 km/h, but still feasible. Conversion of the outside lane, usually meant for slower traffic, would be so justified if the outer paint stripe were moved a bit (say, 0.4 meter) into the emergency pullover-parking strip.

Stations

The stations for load/unload of microcars are located every 10-km above the freeway. This arrangement gives the microcars access to the transporters without interfering with conventional traffic. The station shown overhangs the typical 60-meter freeway width due to the autoloader design.

The space beneath the main platform contains parking for the small percentage of commuters who work in the crowded central business district (CBD) where shuttles or taxis supplement walking.

Maglev ramps are 220 meters long, being the only sections of the guideway that need be elevated.

Staging

A widened staging area is provided just before loading so as to permit juggling of microcars. This operation is desired so as to cluster embarking microcars to match destination stations as they proceed into a loading cycle (resembling a marching band breaking out into platoons at a football half time).

The complexity and timing of the staging operation is such that automation is desired to minimize delay and avoid the occasional snarl due to human error, if manually driven. Control data cables are laid into the roadway ramp and staging area, permitting 'hands off' remotely-controlled driving of microcars from the freeway to the loading pallets. The scheme shown carries two forward-facing microcars abreast. It was considered a requirement that each microcar be able to embark or debark at any station independently. A 30-sec. cycle from transporter stop to start was the design target.

Autoloader

Rapid load/unload of microcars is essential to attract a maximum number of patrons: delays in excess of two minutes will make those needing only a 10-20 km 'hitch' decide to drive the conventional way. The loading platform (and thus the station) can be made much narrower by swiveling the pallets 45 degrees clockwise for debarking cars, then 90 degrees counter-clockwise to accept embarking cars.

A simpler scheme from that shown is to load/unload the cars by a drive on/drive off operation. In its simplest form, this requires a lateral-facing car onboard the transporter. The lateral stowage permits a very simple loading operation, the cars being either manually or remotely driven. An unload/load cycle within 10 sec. is achievable with this method, particularly if automated. Another advantage of this method is that the station footprint can more readily fit within the freeway or arterial width.

Transporter Design

Lateral versus forward-facing cars aboard the transporter is a major design consideration. A disadvantage of lateral-facing cars is that conventional-length cars, such as today's ICV, cannot be accommodated in lateral loading.

In the case of forward-facing conventional ICE cars, the transporter can carry only one-third as many cars as with the Dual Mode microcar. But being able to accommodate the longer conventional ICV may be important for gaining early acceptance of Dual Mode. Thus, transporter designers in the early part of the 21st century will be presented with a challenge, as the most favored commuter car evolves from a 5-meter long ICV to a 2.5-meter long EV. A modular design that could accept a variable mix of lengths and widths, without wasting valuable transporter capacity, would be ideal.

Example Conversions to Microcar Carrier

The 28-meter long O-Bahn bus could be converted to a microcar transporter by replacing the body structure with a double-deck configuration: 16/deck for a total of 32. The 2.5-meter long microcars would handily fit in a lateral orientation, this also being favored for ease of unload/load.

O-Bahn Capable of transporting 32 Nissan Hyperminis in double-deck configuration

HSST maglev capable of transporting 32 Tulips

The HSST-200 requires modification above the chassis to carry 32 microcars. The weight of the microcars, containing up to 128 passengers in the four-passenger model, is exchanged for the158 passengers, their seats, and air conditioning equipment of the passenger-only version. Two gull wing doors on each side are required because of the bi-directional capability; that is, a transporter operating on a North-South route would retain that orientation because the front/rear ends of the 40-meter long articulated transporter are identical.

Energy Consumption

Energy cost to transport 32 microcars on the HSST-200 is $0.23/km (based on 10 km inter-station spacing, average 150 km/h, $0.037/kwh@50kv feed). In comparison, the energy costs (from the same power utility) to drive each microcar are $0.007/km, but at less than half the maglev transporter speed.

Central Control (CC)

The CC sub-system coordinates efficient utilization of all system elements using modern communication links, computers, and the all-important software. The location and status of every microcar and maglev truck is known at all times by the CC computer. The Global Position System (GPS) receiver onboard the microcar, and keyboard entries from each driver are sent to CC via digital multiplex superimposed on the cellular phone link. Since microcar activity around stations during rush hour will resemble a beehive, a high degree of automation is desired to assure delay-free load/unload action.

Load/Unload Management

The central computer assigns microcars, desiring to embark, to empty (or debarking) berths in arriving transporters. This berth assigning process begins when commuters start their trip at the home driveway, entering their destination on the keyboard in the dash of the microcar.

It is not reasonable to expect clusters of microcars, based on a common destination station, to arrive simultaneously at the departure station along with their assigned transporter. Accordingly, juggling is done in the two-lane moving queue on the station approach ramps, assembling the clusters by the time they reach the loading platform. It is possible in early versions of Dual Mode to direct this assembly by automated commands to drivers through the cellular phone link. But remote control using Intelligent Transportation Systems (ITS) technology is much preferred.

Transporter Control Sub-System

A modification of the automatic transporter control sub-system is required to realize the growth goal of 80 meter minimum headway, required for 20 lane equivalent throughput of conventional traffic. In order to achieve this capacity, the crude century-old spacing criteria for conventional railways must be set aside, recognizing the fail-safe monitoring and control technology now available. Speed commands to individual transporters and switch commands to the guideway are CC automated functions. Back-up manual control is available for special operations. Fail-safe operation is a design requirement. For example, a major failure in a transporter results in simultaneous emergency braking of all succeeding transporters that threaten to overrun.

Demonstrator (demo)

Since the microcars, transporters, stations, guideway, and central control are designed as an integrated system, they should not be installed piecemeal into an existing ground transportation system without first conducting a proof-of-concept demonstration. The purpose of the demo is to establish patron use patterns, fine-tune operating software, proof-test hardware, and gain operational experience.

Test Facility

To ensure that all the components of the system play together requires a working model, complete with station, autoloader, test track, and CC. The autoloader, automated clustering of microcars on the staging ramp, and the CC software that coordinates this activity are all critical to delay-free operation.

However, a primitive (early) system, employing a rubber-tired chassis-similar to the O-Bahn bus-and transporting conventional-sized cars, is also possible. Such a low-tech demo would require less system-level testing, emphasis being placed on station and autoloader design. The guideway, using conventional roadways-either at-grade or elevated- should plan for conversion to maglev, consistent with the long-term goals to provide the ultimate transit system for the City of the Future.

For further details, contact Dave Petrie, Petrie Transit Consultants, 811 So. 273rd Ct. Des Moines, WA USA, Phone: 253-946-6619.

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Last modified: April 19, 1999