Transportation Research Record 1791 113
Paper No. 02-3857
To reduce transportation emissions and energy consumption, policy
makers typically employ one of two approaches—changing technology
or changing behavior. These strategies include demand management
tools, such as ridesharing and vehicle control technologies that involve
cleaner fuels and fuel economy. Despite the beneﬁts of a combined pol-
icy approach, these strategies are normally employed separately. Nev-
ertheless, they have been linked occasionally, for instance in the electric
station car programs of the 1990s. Station cars are vehicles used by
transit riders at the start or end of a trip. In 1990, the California Air
Resources Board (CARB) focused on reducing mobile air pollution by
mandating that automakers introduce clean vehicles through its Zero-
Emission Vehicle (ZEV) Mandate. In 1998, signiﬁcant ﬂexibility was
introduced through partial ZEV credits for very-low-emission vehicles.
In 2000, CARB left the ZEV mandate intact, but began considering new
approaches, including station cars and carsharing. Carsharing is the
short-term use of a shared-use vehicle ﬂeet. In January 2001, recogniz-
ing the potential for station cars and carsharing to further improve air
quality by reducing vehicle miles traveled—particularly with transit
linkages—CARB proposed additional ZEV credits for vehicles in such
programs. Thus, the mandate would formally link demand management
and clean vehicles. Explored are carsharing and station car develop-
ments, lessons learned, the ZEV mandate, and the proposed credit
structure. Finally, policy and research recommendations are discussed
for enhancing the success and effect of this combined approach.
An expanding economy and population means expanding travel
demand. The beneﬁts of increased travel are large. But the environ-
mental and other unpaid social costs are also large, especially when
travel is by single occupants in light-duty vehicles.
Vehicle travel is expected to double over the next 20 years in Cal-
ifornia and increase more than 50% across the United States, result-
ing in more congestion, wasted time, and worsened air quality (1).
Meanwhile, total highway capacity in the United States is barely
increasing, with only about 2% added (in lane miles) over the past
30 years. The next few decades thus present a signiﬁcant challenge—
how to accommodate growing travel demand while limiting vehicle
emissions and energy consumption.
One response is enhanced transit. At present, only 4 to 5% of the
nation’s 118 million commuters use transit (2). One reason for low
transit usage is the sparseness of transit service; most people do not
have easy access to transit stations at the home or destination end of
a trip. Carsharing and station cars offer an innovative solution to tran-
sit access; they provide customers with short-term use of a vehicle to
drive to and from a transit station and other locations (3).
Innovative policy approaches are needed to address energy, air
quality, and congestion concerns. The universe of strategies may
be grouped into those that change behavior and those that change
technology. Travel-demand-management (TDM) strategies, such as
ridesharing, parking restrictions, and road pricing, are examples of
behavioral strategies. TDM strategies reduce and eliminate auto trips
and improve the efficiency of the transportation system. Technology-
targeted strategies aim to enhance the attributes of a speciﬁc tech-
nology. These strategies include requirements to use cleaner fuels,
promulgation of more stringent emission standards, and government-
funded technology research and development.
Typically, these two policy approaches (TDM and technology-
targeted strategies) are employed separately (4). There are several
exceptions nevertheless. For instance, ridesharing rules in Los Ange-
les provide credit for use of alternative fuels; tax credits are often pro-
vided for clean-fuel vehicles to encourage individuals to purchase and
use them; and zero-emission vehicles (ZEV) are allowed to use high-
occupancy-vehicle lanes in many regions. It is widely understood,
though, that large synergies result from a combined approach (5, 6).
A potentially attractive synergy can be examined: the integration
of clean vehicles with carsharing and station cars. The policy mech-
anism is California’s Zero-Emission Vehicle (ZEV) Mandate. The
motivation and historical precedent for the integrated ZEV initiative
was a series of electric station car programs launched in the 1990s
(7–9). The linkage between the ZEV mandate and carsharing and
station cars is the topic discussed.
CARSHARING AND STATION CARS
The principle of shared-use vehicles is simple: individuals gain the
beneﬁts of private car use without the costs and responsibilities of
ownership. Instead of owning one or more cars, a household or busi-
ness accesses a ﬂeet of shared-use vehicles on an as-needed basis.
Individuals gain access to vehicles by joining an organization that
maintains a ﬂeet of cars and light trucks in a network of locations.
Generally, participants pay a fee each time they use a vehicle (3).
Station cars are often shared, although not always. They facili-
tate transit access either on the home or destination end of a trip.
Linking Clean-Fuel Cars, Carsharing, and
Station Car Strategies
Susan A. Shaheen, John Wright, and Daniel Sperling
S. A. Shaheen and J. Wright, Partners for Advanced Transit and Highways
(PATH), 1357 South 46th Street, Building 452, Richmond, CA 94804-4648.
D. Sperling, Institute of Transportation Studies, University of California at Davis,
Davis, CA 95616.
Carsharing can be thought of as organized short-term car rental—
often located near transit stations—accessible in convenient locations
throughout neighborhoods, office parks, and college campuses. Car-
sharing organizations (CSOs) are most often found in dense metro-
politan areas, distributed throughout a dense network of neighborhood
lots. Barth and Shaheen, in a paper in this Record, observe that the
concepts of carsharing and station cars are “merging” increasingly so
that they include both elements: transit linkages and distributed lots.
Carsharing and station cars are most effective and attractive when
seen as transportation modes that ﬁll the gap between transit and pri-
vate cars and can link to other transportation modes and services.
For long distances, one might use a household vehicle, air transport,
rail or bus, or a rental car; and for short distances, one might walk,
bicycle, or use a taxi. But for intermediate travel, even routine activ-
ities, one might drive a shared-use vehicle. Shared cars provide other
customer attractions: they can also serve as mobility insurance in
emergencies, and as a means of satisfying occasional vehicle needs
and desires such as carrying goods, pleasure driving in a sports car,
or taking the family on a trip (3, 10). The focus here is primarily on
European (carsharing history and lessons learned) and U.S. activi-
ties. Nevertheless, carsharing and station cars have gained increas-
ing popularity in Canada and Asia, particularly the use of advanced
technologies and electric vehicles in Japan.
Carsharing History and
Lessons Learned from Europe
The earliest and broadest carsharing experiences have been in
Europe. Carsharing emerged largely from individuals who sought
the beneﬁts of cars but were ideologically opposed to widespread
car use. One of the earliest experiences with carsharing can be traced
to a cooperative, known as Sefage, which originated in Zurich,
Switzerland, in 1948 (11). Elsewhere, a series of “public car” exper-
iments were attempted, but failed, including an initiative known as
Procotip, begun in Montpellier, France, in 1971, and another called
Witkar, deployed in Amsterdam in 1973 (12, 13).
In the late 1980s and early 1990s, many carsharing efforts were
initiated in Europe and initially supported by government grants.
Most involved the shared use of a few vehicles by a group of indi-
viduals. Most found it difficult to make the transition from grass-
roots, neighborhood-based programs into viable business ventures.
They miscalculated the number of vehicles needed, placed too great
an emphasis on advanced technology, or were ineffective in their
marketing. Many failed organizations merged or were acquired by
Those that thrived were more professional, and they integrated
advanced electronic and wireless technologies. But even today, car-
sharing accounts for only a tiny amount of travel in all but a hand-
ful of locations. The largest organization, Mobility CarSharing,
has 2,000 cars and 50,000 customers in 900 locations throughout
Switzerland. In Germany, about 75 organizations serve approximately
40,000 customers with about 1,500 vehicles.
Carsharing activity and interest continues to increase. Italy’s Min-
istry of the Environment recently invested 5 million (U.S.) dollars for
a national carsharing program. Operations were planned in four ini-
tial cities for Fall 2001, leading to a total of 15 deployments. Further,
in June 2001, Germany’s railway announced that they would launch
“dbRent”—a carsharing and bike service throughout the nation. In
Europe, there are over 200 CSOs operating nearly 4,000 vehicles.
114 Paper No. 02-3857 Transportation Research Record 1791
Early History of U.S. Carsharing and
Station Car Programs
In the United States, two formal carsharing demonstration research
projects were conducted in the 1980s. The ﬁrst was Mobility Enter-
prise, operated as a Purdue University research program from 1983
to 1986 in West Lafayette, Indiana (12, 13). Each household leased
a very small “mini” car for short local trips and was given access to
a shared ﬂeet of “special purpose” vehicles (i.e., large sedans,
trucks, and recreational vehicles).
In this ﬁeld test, the dedicated minivehicles leased by participants
were used for 75% of the households’ vehicle miles traveled (VMT).
In contrast, the carsharing ﬂeet was only used 35% of the time that it
was available to households throughout the experiment.
A second major U.S. carsharing project was the Short-Term Auto
Rental (STAR) demonstration in San Francisco (12). The STAR com-
pany operated as a private enterprise from December 1983 to March
1985, providing individuals in an apartment complex use of a short-
term vehicle (for a few minutes up to several days). Feasibility study
funds were made available from the Urban Mass Transportation
Administration and the California Department of Transportation.
Users paid on a per-minute and per-mile basis until a maximum
daily rate was reached. The members shared a ﬂeet of 51 vehicles
(44 cars, 5 wagons, and 2 light-duty trucks), with 10 additional vehi-
cles available as backups during periods of peak demand. Membership
peaked at approximately 350 participants (14).
This project failed halfway through the planned 3-year program.
The primary problem was that many tenants were students who
shared apartments and were not actually listed on the lease. Thus, it
was often difficult to obtain vehicle payments from “unofficial” ten-
ants. Another failing was the pricing structure of STAR: it encour-
aged long-term (more than 24-h), as well as short-term (less than
24-h) rentals. Long rentals sometimes resulted in long-distance tow-
ing charges when the old, often poor-quality cars broke down several
hundred miles from San Francisco. STAR’s management tried to cut
costs by purchasing used economy-class vehicles, but this resulted in
high repair costs. Also, STAR apparently offered too many models
in each vehicle class, leaving members dissatisﬁed when a particular
car was unavailable (Martin Russell, unpublished data).
A more recent U.S. research project was a 2-year (1996 to 1998)
study of station car rentals at Bay Area Rapid Transit (BART) district
stations. For this BART project, Cervero et al. (15, 16) conducted an
early market assessment of station cars using a stated-preference sur-
vey. Nearly 50 electric vehicles were used, including forty Personal
Independent Vehicle Company City Bees from Norway, two Toyota
recreational active vehicles with four-wheel drive (RAV-4s), and ﬁve
Kewets from Denmark (17).
In addition, several station car programs were launched in the mid-
1990s by rail transit operators seeking to relieve parking shortages at
stations (and desiring to avoid the high cost of building more park-
ing infrastructure), electric utilities (eyeing a potential market for
battery-powered electric vehicles), and air quality regulators (seek-
ing to reduce vehicle usage and pollution). Many of these programs
struggled with the high cost and low reliability of ﬁrst-generation
electric cars. Although shared use is the goal of many station car
programs, as of early 2002 only a few had aggressively incorporated
shared-use practices (i.e., the programs typically have low user-to-
vehicle ratios). Nonetheless, it was these experiences of “zero-
emission” battery electric vehicles, ostensibly used to reduce travel,
encourage transit, and reduce pollution that inspired California
regulators to integrate the carsharing and station car concepts into
the ZEV mandate credit structure.
Current Status of U.S. Carsharing and
Station Car Programs
In the United States today, there are 7 active CSOs (Table 1), 4 sta-
tion car programs (Table 2), 3 carsharing research pilots [CarLink,
Intellishare, and ZEV Network Enabled Transport (ZEV-NET)], and
over 10 programs currently planned for 2002 and 2003. Most CSOs
follow the predominant European operational model: private individ-
uals access cars from nearby neighborhood lots, returning them to
the same lot. Several of these programs use advanced technology
Shaheen et al. Paper No. 02-3857 115
(i.e., smartcards, Internet-based reservations, and vehicle tracking)
to facilitate reservations, operations, and key management. Four are
run as commercial businesses, six are nonproﬁts, one is a cooperative,
and three are research pilots.
The Dancing Rabbit Vehicle Cooperative, located in Rutledge,
Missouri, has been in operation since 1998 as a cooperative. Car-
Sharing Portland (now Flexcar Portland) was the ﬁrst full-scale car-
sharing program in the United States, opening its doors in 1998.
Flexcar started in Seattle in 1999, acquired CarSharing Portland in
April 2001, and expanded to Washington, D.C., in November 2001.
In 2000, another major commercial organization, Zipcar, launched
in Boston and has recently expanded into the Washington, D.C., area
and New York City. Carsharing Traverse in Michigan launched in
2000. City CarShare, a San Francisco nonproﬁt organization, began
Program Name, Location &
Dancing Rabbit Vehicle
Cooperative (Rutledge, MO)
Program is operated in the Dancing
Rabbit Ecovillage cooperative. Vehicles
are fueled with biodiesel.
Flexcar (Seattle, Washington;
Washington, D.C. Metropolitan
Area; and Portland, Oregon)
(Note: Flexcar Portland was
formerly CarSharing Portland)
A neighborhood carsharing model with a
strong transit linkage. Flexcar acquired
Portland (first full-scale commercial
CSO in the U.S.) in 2001. Flexcar
launched operations along D.C. Metro
line in November. Gas-electric hybrid
vehicles are incorporated into all fleets.
(Traverse City, MI)
Program is located in a community of
15,000 residents. Approximately 18 of
30 members are active users.
Washington, D.C. Metropolitan
Area; and New York City)
Zipcar operates a neighborhood
carsharing model with corporate,
individual, and household membership
packages. They are planning to add gas-
electric hybrid vehicles to their fleet.
They expanded to the Washington D.C.
metropolitan region in 2001, and then
into the New York metropolitan area in
This CSO operates a neighborhood
carsharing program, with one electric
(San Francisco, Berkeley, and
City CarShare is a neighborhood
carsharing program with household and
business memberships. Vehicles are
often placed proximate to public transit
stations. They began expansion into
Oakland in the fall of 2001 and are
continuing to expand into Berkeley.
Roaring Fork Valley Vehicles
This CSO operates a neighborhood
carsharing program with one gas-electric
hybrid vehicle. They are located in a
small community with many seasonal
This program operates a neighborhood
carsharing model, with vehicles
proximate to public transit. They plan to
start with two vehicles and began
accepting applications in March 2002.
Clean Mobility Center
(Long Beach, CA)
This Center will launch with five electric
Th!nk vehicles, a variety of electric
bicycles, scooters, and conventional
bikes. Vehicles will be available for
shared use at Metrolink stations.
TABLE 1 U.S. Carsharing Programs
in 2001 and grew to 24 vehicles in its ﬁrst 6 months. In the fall of
2001, City CarShare contracted to expand its operations into the East
Bay communities of Oakland and Berkeley; several locations will be
near BART stations. Other programs that launched in 2001 include
Boulder CarShare and Roaring Fork Valley Vehicles in Aspen.
As of Spring 2002, two more CSOs have recently launched. I-Go
in Chicago, Illinois, began recruiting members in March. The Clean
Mobility Center, in Long Beach, California, publicly announced its
launch in April 2002. They will provide electric vehicles, bikes, and
scooters for shared-use along the Metrolink rail line.
The Clean Commute Program began as a demonstration in 1995.
In June 2001, they reported seven members and five vehicles. In
Fall 2001, this program announced plans to expand to 100 Ford
Th!nk vehicles along the commuter rail line in the New York City
suburbs. Power Commute launched its station car operations in
1997. This program is operated by a transportation management
association and maintains a stable membership of 20 users. In 2000,
the Anaheim Transportation Network and Hertz-BART programs
started. Both focus on providing transit linkages to commuters and
Three “smart” carsharing research pilots are currently in operation
in California. CarLink II was launched in Northern California in
July 2001; it builds on the 1999 CarLink I ﬁeld test and is a transit-
based commuter program with 20 Honda Civics (18–20). Southern
California’s Intellishare program, which incorporates 25 Honda EV
Plus electric vehicles, smartcards, and onboard computer technolo-
gies, operates under the direction of University of California, River-
side researchers. The third, ZEV-NET is a public–private partnership
between Toyota and University of California, Irvine (UCI), consist-
ing of 15 e-coms and smart technologies, shared among six employ-
ers located in the UCI office park. ZEV-NET plans to link with
transit 10 e-coms, 30 RAV-4 electric vehicles, and 10 Prius vehicles
As of March 2002, U.S. carsharing and station car programs col-
lectively claimed 8,689 members and operated 419 vehicles from
116 Paper No. 02-3857 Transportation Research Record 1791
227 locations. Strong interest in carsharing is continuing in other
U.S. cities. In 2002 and 2003, additional efforts are planned in San
Diego, Los Angeles, Sacramento, and San Francisco (Presidio), Cal-
ifornia; Denver, Colorado; Newark, Delaware; Atlanta, Georgia;
Silver Spring, Maryland; Minneapolis, Minnesota; Philadelphia,
Pennsylvania; and Madison, Wisconsin.
Until the past decade, almost all efforts at organizing CSOs resulted
in failure. For a variety of reasons, a new era began in the late 1980s
in Europe. A number of CSOs are now ﬁrmly established and on steep
growth trajectories. These organizations appear to provide large social
beneﬁts. Car travel and car ownership diminish greatly when individ-
uals gain access to carsharing services, which is far greater than with
virtually any other demand management strategy known. Particularly
appealing is that carsharing represents an enhancement in mobility
and accessibility for many people, especially those who are less
Some lessons in how and where to launch carsharing programs are
becoming apparent. On the basis of a review of the literature, car-
sharing programs can be concluded most likely to be economically
successful when they provide a dense network and variety of vehi-
cles, serve a diverse mix of users, create joint-marketing partner-
ships, design a ﬂexible yet simple rate system, and provide for easy
emergency access to taxis and long-term car rentals. They are more
likely to thrive when environmental consciousness is high, driving
disincentives such as high parking costs and traffic congestion are
pervasive, car ownership costs are high, and alternative modes of
transportation are easily accessible.
An even more important lesson, though not well documented, is
the need for partnerships and mobility providers to offer enhanced
products and services. More business-oriented carsharing programs
thrive by acquiring those that fail or lack strong leadership. But to
Project Name, Location &
Clean Commute Program
(New York, NY)
This program initially began operations
in 1995 with six electric vehicles,
driven from a train station to an IBM
facility. In fall 2001, new efforts were
launched to expand to a total of 100
Ford Th!nk electric vehicles along a
commuter rail line.
Power Commute deploys electric
vehicles to aid users in traveling among
one train station and several work sites:
Lucent, Bauer, and Verizon Wireless.
Network RAV4 Program
Workers carpool in electric vehicles
from two Metrolink stations to their
Hertz runs this program based out of
the Fremont BART station, which
includes two Ford Th!nk electric
vehicles. Vehicles are also used as
traditional rental vehicles. Hertz plans
to expand program to a second BART
station (Colma) in 2002.
TABLE 2 U.S. Station Car Programs
retain customer loyalty, they must improve services and reduce
costs. Two linked strategies are being followed:
1. Coordinate and link with other mobility (e.g., smart parking
management) and nonmobility (e.g., employers and residential
developers) services; and
2. Incorporate advanced communication, reservation, and billing
technologies in conjunction with signiﬁcant membership growth.
But advanced technologies are expensive and linking with other ser-
vices is successful only if the customer base is large, so most car-
sharing programs have either remained quite small or followed a
notable growth trajectory.
Taking a longer view, carsharing companies may be the prototype
of an entirely new business activity: innovative mobility service com-
panies. As vehicle ownership proliferates and vehicles become more
modular and specialized, entrepreneurial companies may see an
opportunity to assume the full care and servicing of a household’s or
an individual’s mobility needs in neighborhoods, work sites, transit
stations, and shopping centers, on the basis of mobility management.
These innovative mobility companies might handle insurance, regis-
tration, maintenance, and parking management and could substitute
vehicles as a household’s situation changes. One can imagine a future
in which pioneering carsharing programs combine their operational
expertise with the entrepreneurial capabilities of advanced technol-
ogy suppliers to create mobility services that enhance our social,
economical, and environmental well-being. Although experience
and evidence are not extensive, there is reason to believe that “smart”
carsharing concepts and technologies provide the foundation to cre-
ate new transportation solutions. It is impossible to know the ultimate
market for carsharing and its derivatives and spin-offs, although some
new directions are emerging (e.g., linkages to employers, residential
and commercial managers, developers, and parking management
facilities). It is difficult to estimate demand for new technologies and
new attributes when customers have no experience with those prod-
ucts and attributes and when those attributes remain somewhat uncer-
tain. Further, determining the demand for carsharing is especially
difficult because it implies some reorganization of a household’s
travel patterns and lifestyle. People use and view their cars in many
different ways that are poorly understood. They value them not only
for utilitarian travel, but also for storage, quiet time away from fam-
ily and work, and office space. How important are these uses and
activities and for whom? How much inconvenience are people will-
ing to accept in return for less cost? And how much value will be
associated with such services?
It is also impossible to know what effects carsharing systems and
their innovative mobility offshoots will have. Early evidence from
Europe suggests up to a 50% reduction in vehicle travel—the result
of travelers now having easier access (and egress) to transit stations
and a greater share of ﬁxed costs shifted to variable costs (11, 21).
One would expect the net effect of these new types of ownership pat-
terns and innovative mobility services to be less vehicle travel, for
the reasons cited above. Indeed, this belief is what motivates many
of the pioneers and sponsors of carsharing and station car programs.
But the future evolution of these services and usage patterns is still
highly uncertain and indeed will be inﬂuenced by many factors,
including the ZEV mandate.
To summarize, this section provided an overview of carsharing
and station car activities in Europe and the United States and lessons
learned. Next is discussion on the California Air Resources Board’s
(CARB) proposed linkage of clean-fuel vehicles, through its ZEV
Shaheen et al. Paper No. 02-3857 117
mandate to transportation systems, which include carsharing and
station car services.
CALIFORNIA’S ZEV MANDATE AND
In 1990, CARB adopted the low-emission vehicle (LEV) program,
a long-term strategy to reduce air pollution from mobile sources
through the gradual introduction of LEVs. Included in the LEV pro-
gram is the ZEV mandate, which sets production requirements for
ZEVs in future years. Pure ZEVs are deﬁned as vehicles that produce
no tailpipe emissions. At present, battery electric vehicles are the
only commercially available vehicles that meet this speciﬁcation.
Originally, the ZEV mandate required that automakers produce
at least 2% ZEVs by 1998, 5% by 2000, and 10% by 2003 (the per-
centage was applied to cars only, not light trucks, and applied to the
seven largest suppliers to California in 1998 and 2001 and then
expanded to include all but the very smallest suppliers in 2003). The
credits were, and still are, tradable, with a $5,000 ﬁne imposed for
each vehicle not made available for sale.
The ZEV mandate was subject to biennial reviews up to the year
2000. In 1992 and 1994, no changes were made. In 1996, on the basis
of assessment of current battery technology, CARB modiﬁed the reg-
ulations to allow time for technology development. They eliminated
the production requirements for 1998 to 2002, but retained the 10%
requirement for 2003, in exchange for a Memorandum of Agreement
with the seven major automakers, that is, DaimlerChrysler, Ford,
General Motors, Honda, Mazda, Nissan, and Toyota. The automakers
agreed to do these things:
•Continue to invest in ZEV and battery research and develop-
•Produce up to 3,750 advanced battery-powered ZEVs from
1998 to 2000.
In 1998, CARB introduced signiﬁcant ﬂexibility into the pro-
gram. Under the new regulations, automakers could earn partial
ZEV (PZEV) credits as incentives for producing very-low-emission
conventional vehicles (e.g., gasoline vehicles with extremely low
emissions). Additional incentives were provided to encourage the
use of advanced componentry, and the introduction of “pure” ZEVs
before the 2003 deadline. Up to 6% of the 10% requirement in 2003
could be met with PZEVs (22).
At the 2000 review, CARB chose to leave the ZEV mandate
intact, but asked staff to present proposals to address the challenges
associated with a successful long-term ZEV implementation pro-
gram. At a board meeting on January 25, 2001, several staff pro-
posals were approved that granted automakers even more ﬂexibility,
whereas more stringent requirements were added in future years.
The approved changes include
•In early years, the required number of pure ZEVs are reduced
by approximately half, from 4% to 2% of total sales.
•Advanced technology PZEVs (AT-PZEVs) such as compressed
natural gas, gas–electric hybrid, or methanol fuel cell vehicles can
satisfy up to one-ﬁfth of the 10% requirement (i.e., equivalent to 2%
of total vehicle sales).
•ZEV credits will be given to automakers who produce vehicles
for demonstration projects to encourage participation in programs
such as the California Fuel Cell Partnership.
•An additional credit multiplier is offered based on the vehicle’s
•Beginning in 2007, the sales ﬁgures used to calculate each
automaker’s ZEV requirement will be broadened to include sport
utility vehicles, pickup trucks, and vans, thereby increasing the actual
number of ZEVs required.
•The percentage requirement of ZEVs will gradually increase,
from 10% in 2003 to 18% in 2018.
•Additional credits are provided for vehicles placed in “trans-
portation systems” (22).
This last change was made in recognition of the potential for car-
sharing and station cars (or transportation systems) to improve air
quality by reducing total VMT and cold-start emissions (because of
shared-use and the linkage of clean-fuel vehicles to transit). The staff
proposal, which was approved on January 25, 2001, provided a gen-
eral description of the transportation system’s credit mechanism.
Additional proposed changes released on October 31, 2001 expanded
and further deﬁned the program. Under the most recent proposed lan-
guage, each ZEV vehicle placed in an approved carsharing/station car
program by automakers would receive additional credits as shown in
Table 3. Note that automakers are not required to link “smart” car-
sharing vehicles to transit in such programs but are eligible for addi-
tional credits if they do so. Furthermore, ZEV vehicles placed at
transit stations are eligible for additional ZEV credit, without sharing
or use of advanced technology (23).
LINKING ZEV VEHICLES TO CARSHARING AND
STATION CAR PROGRAMS
The motivation for the “transportation systems” portion of the ZEV
regulation was twofold. First, CARB staff recognized that a signiﬁ-
cant beneﬁt of carsharing is short-term customer access to a variety
of vehicle models. Thus, a wide range of ZEV vehicles (e.g., electric,
compressed natural gas, and hybrid vehicles) could be introduced into
carsharing programs, allowing customers to select the most appropri-
ate clean-fuel vehicle for their trip needs on the basis of driving range,
fueling infrastructure availability, number of passengers, and so forth.
Accordingly, the transportation systems credit structure awards addi-
tional credits for ZEV, AT-PZEV, and PZEV vehicles incorporated
into carsharing and station car programs. Both carsharing and sta-
tion car programs are perceived to offer a potential market for the
near-term placement of ZEV vehicles.
The board also believed that such programs (particularly shared-use
vehicle programs linked to transit) are well matched to the perfor-
mance characteristics of battery electric vehicles (e.g., 113 to 120 km
on a charge) because of the short length of many station car and com-
118 Paper No. 02-3857 Transportation Research Record 1791
muter carsharing trips. Furthermore, cold-start emissions can be
reduced through the use of clean-fuel vehicles (e.g., battery electric
and fuel cell vehicles, fueled by hydrogen) for multiple trips through-
out the day. Shared-use vehicle programs also could make use of
smaller electric vehicles, which might serve as local neighborhood or
city vehicles. Since smaller vehicles would need much less energy and
smaller batteries, they would be relatively less expensive to operate.
A second motivation was to link the ZEV mandate to transporta-
tion strategies that reduce vehicle usage. Carsharing and station car
programs can result in more transit-based trips, thus reducing vehi-
cle travel and air pollution. In their proposal, CARB staff speciﬁed a
direct link to transit (i.e., the car must be placed at or close to a tran-
sit station) for ZEV vehicles to be eligible to receive additional “tran-
sit linkage” credits. This is an important point, as many carsharing
operators claim that users increase transit ridership as a result of car-
sharing, often without a direct transit linkage (e.g., a lot located at a
To summarize, carsharing and station cars provide a potential mar-
ket niche for LEV and a modal alternative that offers the promise of
reduced vehicle travel. The current proposal of CARB staff for grant-
ing extra credit to automakers is presented in Table 3. As proposed,
the use of these transportation system credits would be capped at an
amount equivalent to one-half of a manufacturer’s pure ZEV obli-
gation, one-fourth of the AT-PZEV category, and one-thirtieth of the
PZEV category (23).
As indicated, a battery electric vehicle used as a station car, even
without vehicle sharing, would receive three vehicle credits. If this
transit-linked vehicle is also part of a carsharing program, with
advanced technologies used for reservations, billing, and manage-
ment, then it receives an additional six credits. For example, a 2003
Th!nk city vehicle (European model) is eligible for 1.25 credits
(including early introduction credits). If placed in a carsharing pro-
gram, linked to transit (or transportation system) with advanced
technology, it would be eligible for an additional 9 credits, totaling
10.25 credits for one individual vehicle.
If hybrid or natural gas vehicles (categorized as AT-PZEV) are
used, then they would receive four additional credits if part of a smart
carsharing application and another two if linked to transit (or used as
station cars). For instance, a 2003 natural gas Civic is eligible for 2.0
credits (again, reﬂecting early introduction). Similarly, if placed in a
carsharing program linked to transit with advanced technology, this
vehicle would be eligible for an additional 6.0 credits, for a total of
8.0. PZEV vehicles (such as very-low-emitting gasoline cars) are also
eligible for additional credits, but in smaller amounts. To summarize,
the additional credits offered here are the equivalent of up to several
vehicles—a signiﬁcant incentive to vehicle manufacturers.
The addition of transportation system credits in the ZEV mandate
could have a substantial effect within and outside California. The
(i.e., battery electric
PZEV (e.g., compressed
natural gas vehicles and
(i.e., super ultra low
emission vehicles with
Vehicles and Advanced
Transit Linkage 3
Total Possible Additional
TABLE 3 ZEV Credit s for Vehicles Placed in Carsharing and Station Car Systems (Proposed)
effects outside California result in part from the technology and con-
cepts being demonstrated and publicized—but also because other
states are also adopting the ZEV mandate. Initially, New York, Mass-
achusetts, Vermont, and Maine adopted California’s original ZEV
mandate; and others may follow in the future (24). If other states adopt
the mandate, then they must adopt the entire package of embedded
rules (although ﬂexibility is available with regard to the timing and
phase-in of the various requirements). This requirement is rooted in a
federal law that requires all states to adopt either the national emission
standards (as promulgated by the U.S. Environmental Protection
Agency) or California’s. There is no “third” standard allowed at pres-
ent. Thus, California’s ZEV credits for carsharing and station car
vehicles will have a signiﬁcant effect nationally. Widespread growth
of shared-use vehicle programs in California will, if successful, pro-
vide a highly visible model for the nation, automakers, information
technology companies, and third-party service operators interested in
expanded market opportunities. And the transportation systems pro-
visions of the ZEV mandate will likely inﬂuence how those initiatives
evolve, perhaps sharply.
SUMMARY AND RECOMMENDATIONS
Smart carsharing and station cars provide a promising opportunity
to reduce vehicle travel, and the ZEV mandate has been perhaps the
most effective policy instrument for accelerating the development
and commercialization of clean-propulsion technology. The inte-
gration of carsharing and station cars with the ZEV mandate could
have important implications. This is an illustration of how creative
policy making can be used to integrate behavior and technology
strategies. It is also an illustration of the need for regulators and pol-
icy makers to be ﬂexible and attentive to new knowledge and chang-
ing circumstances. The ZEV mandate of 2001 has greatly changed
since the mandate of 1990. And with the integration of carsharing
and station cars, the technology transformation inspired by the ZEV
mandate may now spread more broadly into the design and use of
passenger transportation systems.
CARB has taken on a broad responsibility. It has been respectful
of its role in the past by periodically revising the ZEV mandate to
reﬂect new knowledge and understanding. To play an effective and
beneﬁcial role as CARB proceeds into broader transportation issues,
it will need to broaden and deepen its expertise and develop new
partnerships and means of information gathering. In 2002, CARB
plans to ﬁnalize this regulation and begin developing strategies to
support these efforts in California. At present, CARB is exploring a
joint memorandum of understanding with two other state agencies
(California Department of Transportation and California Energy
Commission) to support the ZEV–carsharing/station car program
linkage. Issues that CARB will need to explore further include
•Role of advanced technologies in facilitating use and program
•Model approaches (e.g., carsharing and station cars),
•Lessons learned and success factors,
•Need for large-scale and coordinated efforts (e.g., inter-
operability among systems for users),
•Guidelines for assigning ZEV credit,
•Public–private partnerships, and
•Effect assessment (e.g., societal and environmental system
Shaheen et al. Paper No. 02-3857 119
The potential of this combined approach—demand and technol-
ogy management—is signiﬁcant. In upcoming years, planning, col-
laboration, and creativity will be needed to realize the beneﬁts of this
approach. In working together, government agencies, local decision
makers, and private industry have the potential to create large-scale
carsharing/station car programs. Lessons learned will aid in this
process, as well as comprehensive monitoring and evaluation. In
the ﬁnal section, several policy and research recommendations are
outlined for the future.
At present, little is known about the social and environmental effects
of carsharing and station cars. A statistically signiﬁcant database on
carsharing/station car program effects does not yet exist. One cannot
accurately generalize about behavior, viability, and actual social ben-
eﬁts. Furthermore, there has not yet been signiﬁcant “scaling” in any
U.S. test. Indeed, several carsharing programs failed in Europe be-
cause they lacked economies of scale (i.e., too few vehicles and high
overhead rates made proﬁtability difficult to achieve). The hypo-
thesis is that with scale (e.g., 1,000+vehicles) and supportive policies
(e.g., ZEV mandate, reduced or donated “premium” parking spaces,
partnerships with employers and developers, and start-up subsidies),
carsharing programs can become economically sustainable.
Current and future efforts should focus on increasing vehicle and
membership numbers and on introducing the latest labor-saving
technologies to reduce overhead and provide user-friendly services.
To gain a statistically valid data set on system beneﬁts and costs,
Key questions should be answered:
•Can carsharing and station car systems facilitate transit access
and encourage use?
•Can they reduce parking needs at transit and work?
•Can they help attract and retain employees?
•Can they support air quality and other environmental goals?
•Can they encourage more careful tripmaking with regard to
duration and distance traveled?
•Finally, can they become economically sustainable?
To answer these questions will require travel behavior analysis,
market research, and economic analysis, as well as investigation of
environmental and social effects, technologies and services needed,
technology standardization, and institutional issues (e.g., insurance).
Finally, in linking the ZEV mandate to carsharing and station car
programs, an assessment of this policy should be conducted, which
looks at the role of subsidies and incentives that can help foster these
programs, as well as the role of creative partnerships (e.g., transit
discounts, parking incentives, and insurance).
Over the next decade carsharing and station car system success
may depend on how well such programs can integrate advanced
technologies—electronic and wireless systems and clean-fuel vehi-
cles and infrastructure. On the operations side, advanced technologies
need to be further developed to make carsharing services economi-
cally efficient to manage. Key research components include analyz-
ing institutional issues (e.g., determining the ideal institutions for
managing such programs, for instance, nonproﬁts or commercial);
deployment barriers (e.g., insurance costs); and which technologies
and services are necessary from an operational perspective.
On the user side, carsharing services aim to provide as much ﬂex-
ibility and mobility as the private auto. Thus, advanced technologies
are needed to make an individual’s tripmaking more seamless, so
users can easily access carsharing and station car vehicles (even
spontaneously) or switch modes quickly with little hassle. Informa-
tion technologies will be critical to facilitating modal connectivity
and integrating reservations, smartcards, and ﬂeet management sys-
tems to enable convenient vehicle access and billing. Furthermore,
user-friendly interfaces could be expanded to provide real-time trav-
eler information to users, so they will know vehicle locations, traffic
conditions, time and travel costs, and how to use each system.
To conclude, the long-term potential and viability of carsharing and
station car programs could be strengthened through a combination of
•Cost-reduction strategies (e.g., scale, advanced technologies,
•Policy incentives (e.g., parking management);
•Partnerships with employers and developers;
•Increased user revenues; and
•Local program support.
Although these fundamental issues and questions are noteworthy in-
dependently, a focused agenda is needed to help coordinate individual
efforts and to concentrate research and evaluation in needed areas.
The authors acknowledge MollyAnne Meyn and Rebecca Pearson of
Partners for Advanced Transit and Highways (PATH) for their assis-
tance gathering carsharing and station car program data, as well as
numerous carsharing and station car programs that have provided
updates. The authors also thank Conrad Wagner and Martin Bernard
for assistance with carsharing and station car developments. Review
of this manuscript by Chuck Shulock of the California Air Resources
Board was also invaluable. Thanks also go to the California Depart-
ment of Transportation and PATH for generous contributions to this
carsharing and station car research.
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The contents of this paper reect the views of the authors and do not necessarily
indicate acceptance by the sponsors.
Publication of this paper sponsored by Committee on New Transport ation Systems