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A Simulation Model for Managing the Parking Systems
of Kaohsiung: A System Dynamics Approach
Showing H. Young
Tai Ma
Chien M. Chao
National Sun Yat-Sen University
ABSTRACT
This paper tries to develop a simulation model for managing the parking sys-
tems for the city of Kaohsiung. The system dynamics methodology is employed
to formulate the model. The causal structure is compartmented into five sec-
tors: (1) the urban activity/travel sector, (2) the modal split sector, (3)
the parking sector, which comprises parking supply and parking demand subsys-
tems for both curb and off-street parkings, (4) the traffic/parking interact-
ion sector, and (5) the financial management sector, which attempts to deve-
lop causal links between the revenue sources and expenses of the parking sys-
tem. The model provides the city administrators a policy lab for parking
systems management.
- INTRODUCTION
Every automobile trip begins and ends with the storage of the vehicle.
Therefore, parking becomes an integral part of the urban transportation
system. Conventional urban transportation planning efforts emphasize on the
provision of adequate moving and storage facilities for the travelers so that
their desired activities could be accomplished conveniently. However, the
provision of ample roads and parking spaces attracts increasing automobile
usages, which in turn leads to the construction of more roads and parking
spaces; and the cyclical process goes on and on. Due to the immensity of
current urban transportation problems, ranging from congestion to environ-
mental issues, various new approaches to reduce the adverse effects of auto-
mobile travel have been proposed. Many of these policies advocate measures
which encourage shifts from auto to more efficient transportation modes, such
as public transportation, rather than the traditional solution of increasing
highway capacity and enhancing parking availability (Witheford 1972). How-
ever, these policies evoked considerable controversy and disagreement among
planners, transportation engineers, public transit officials, business inter-
ests, politicians, and the public. The variety in the applications of park-
ing management strategies in different locations and development stages and
the broad range of interest groups affected make parking management a complex
and sensitive issue (Parker 1980).
In this paper, we attempt to employ the system dynamics approach to examine
the problems, understand the behaviors in the complex system, and formulate
a causal structure which will help the evaluation of some of the potential
parking management strategies.
THE PARKING PROBLEMS IN THE CITY OF KAOHSIUNG
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The city of Kaohsiung, a big industrial and commercial port city in southern
Taiwan, has been growing rapidly during the last three decades. At present,
the population exceeds 1.3 millions and the container transhipping is ranked
number four in the world. Yet like many other cities in the world, Kaohsiung
now faces various problems in her rapid development process. The traffic and
parking problems in the central business district (CBD) are among the most
serious.
People in Kaohsiung used to be proud of their transportation facilities: the
streets are much wider than those in most of the other cities in Taiwan and
has a reasonably convenient bus transit network. In the 70's, although veh-
icular travel grew with the increased population, average family income, and
other industrial, commercial and land use activities, the transportation sys~
tems accommodated the travel demands adequately in general (Kaohsiung 1984).
However, during the last five to six years when the family income increased
to a certain level, the automobile ownership started to grow at an accelerat—
ing rate, which consequently brought more and more automobiles on the roads.
With the wide streets, the traffic, although crowder than before, is still
not as congested as many of the other big cities in the world. However, the
CBD area does not have enough spaces to accommodate the massive flow of traf-
fic and parking demand. In order to solve the parking problem, the city gov-
ernment invested multimillion dollars to build a ten-story parking garage in
the Yen-Cheng District. However, the utilization rate of the garage has
never been over 40 percent of its capacity. There are two major reasons for
the underutilization: (1) almost all the other parkings around this garage,
either on-street or off-street, are provided free to the public, and (2) the
CBD area has been shifting gradually from Yen-Cheng District to its adjacent
Shin-Shin District. On the other hand, the insufficient budget allocated to
the management needed for the parking violation enforcement has resulted in
very serious illegal parking problem, which further deteriorates the traffic
condition. A recent survey conducted by the authors shows that over 97 per
cent of the parkings are provided free. The problem of parking violations
is very serious, varying from opposite parking to double or even triple
parking, but less than 4 per cent of the violations received tickets.
With the increasing population and vehicle ownership, the parking problems
in Kaohsiung's CBD area will be more severe and proper parking management
strategies are badly needed.
THE NEED OF SYSTEM DYNAMICS APPROACH
During the past decade, attitudes toward urban growth, environmental pro-
tection, energy conservation, social responsibility, and taxes to support
public transportation programs have noticeably changed. In response to the
problems created by the reliance on auto travel, many planners are now
concentrating on a unified transportation management approach which addre-
sses all elements of the urban transportation system. Parking, being one
of the most important sectors in the urban transportation system, should
gain more attention in the transportation planning process. This is due
to the fact that parked vehicles are easier to control than moving vehi-
cles (Parker 1980).
The parking problems in Kaohsiung do not stand by themselves, they should
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be treated from a systems point of view. That is, the solutions to the prob-
lems should be assessed not on each individual part but on the performance of
the entire system. Thus, the potential parking management strategies should
be evaluated not only by their contributions to the parking and transporta-
tion sectors but also with the considerations of their social, economic, and
environmental impacts to the city of Kaohsiung. The complex, dynamic, and
feedback features of the system merits a system dynamics approach to address
the problem.
THE MODEL
A simplified causal diagram of the model is presented in Figure 1. To ease
the discussion of the model, the diagram is divided into five sectors: (1)
the urban activity/travel sector, (2) the modal split sector, (3) the parking
sector, (4) the traffic/parking interaction sector, and (5) the financial
management sector. These sectors are briefly discussed in the following
sections.
The Urban Activity/Travel Sector
Travel demand in an urbanized area is influenced primarily by its population,
the mobility provided by its transportation systems, the income level of the
people, and its attractiveness in various aspects. The attractiveness of the
area will be reduced with increasing population density, crime rate, traffic
congestion, and air and noise pollution. As the level of income increases,
vehicle ownership increases accordingly for the improvement of mobility. In
most of the cities, social.and commercial activities are concentrated in the
CBD area which absorbs and produces a great amount of trips. However, since
the available space in the CBD area is limited, the concentration of traffic
and parking demand causes a lower accessibility of the area which in turn
reduces the mobility and discourages travel to the area. In this study,
trips are stratified as work-trip and non-work-trip. The attributes of these
two types of trips make their travel and parking demands quite different from
each other.
Modal Split Sector
Trips attracted to the CBD area are then splited into different modes of
travel. In this study we assume two types of modes: transit and automo-
bile. The choice between transit and automobile depends upon their uti-
lities to the travelers. The primary factors of concern are the costs
spent on the trip and the level of service (L.0.S.) of the choosen mode.
The costs include both the monetary costs and the times spent for the trip.
The monetary costs associated with the use of an automobile include the
operating expenses and the out-of-pocket costs spent on the trip and for
parking the car. The time costs consist of three parts: the on-vehicle
travel time, the time spent for parking, and the walking time to the final
destination. The time spent for searching a parking space increases with
the diminution of the availability of parking, which is reflected in the
model by the parking demand to supply ratio in the CBD area.
To transit riders, the only monetary cost is the fare. The time costs
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fr t
Urban Urban NC cap cBD Noise/Air
Populat Lon————At tract iveness«—Social~ CD otegt Sect Pollution
ae od - a aN KR
f Ne fr
Urban 4) Urban +. cBD Energy reakese
Mobility —+~———"» Travel ———__—_» Travel Consunption Congestion
Demand Demand +
+ He
+
|——Income <2
le CBD Transit/ cBD ~?™* cep + cBD
Auto Utility Travel by Travel by Traffic
Vehicle Ratio Transit ‘Auto Volume
Ownership
+
cpp BD cep cap cap
Transit Auto Traffic =———— Traffic Parking
vedlity’ uedlity L.0.8, vic Ratio, Demand
oa
+
Transit CBD Road cBD + cap
1.0.8. Area for Effective Traffic
Ne Traffic Ratio, Traffic “Improvement
Capacity
t H+ +
\ | teaver by cap a CBD Road cBD
tomTransit Road Area Road Area for curb Parking
i Costs for Parking Area Traffic Demand
CBD ‘Avg. CBD off- cp BD off-Street/ |" Gva't
Parking Street Parking curb Parking Curb Parking Aid to
Costs Utility Uedlity Utility Ratio Transport
Me
ty hy,
CBD Off- cD BEfective cep curb CBD Oft- met
Street Parking Curb Parking curb Parking Parking Demand/ Street Parking
Goats Supply sf Costs Supply Ratio Denand
Hy +/—
\ &
cep off- cp off- Parking = cep curd tt cap
Street Parking Street Parking ‘Violation—————p Parking \wtraffic/Parking
(~ Demand/Supply, Management Enforcement Violation Managenent
8
Ratio | we NG (, wBudget
ii - +
CBD Off-Street CBD Off- cBD ofs- CBD Parking Bs
Parking Effective| / Street Parking—te street Parking Violation
Suppl: Supply Uncomplying Supply Uncomply Fine Revenues Fee Revenues
Fine Revenues
Me
a x
CBD off-street , CBD Off-Street cBD Off-Street Parking
Parking «—t— parking Private Land Parking Supply ———w-Revenues
Supply Investment Value Tax Revenues +
J
Pigure 1.
A Simplified Causal Diagram of the Model
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include the walking time from the origin to the station, the time for waiting
the transit, the on-vehicle travel time, the time for transfer, and the walk-
ing time to the final destination. In addition to the monetary and time
costs, the level of crowdness of the transit is also an important factor to
transit riders. When the level of crowdness rises above certain limit, the
utility of transit is reduced, which leads to lower transit ridership.
On the other hand, when more trip makers are shifted from transit to automo-
biles, the total amount of vehicular trips grows rapidly, which results in
traffic congestions and consequent increases in the monetary and/or time
costs for both the transit and the automobiles. It should be mentioned that
in this model, all the cost-related variables are adjusted by the level of
income in the study area. Since the cost variables are the composition of
the time costs and the monetary costs, the adjustment to the time cost and
the monetary cost are positive and negative, respectively. This is because
people of higher income level tend to have higher perceived value of time
and lower perceived value of money.
The split of modes applies only to the "choice riders", those who can choose
between automobile and transit. To those who do not have a choice, they are
captive to the transit, so called "captive riders." Thus, in the model the
automobile ownership is used to adjust the shares of trips taking transit
and automobile. The number of automobile trip makers is translated into the
number of automobile trips through the vehicle occupancy rate assigned.
The numberof automobile trips generated in this sector are then used to
estimate the parking demand in the next section.
The Parking Sector
The parking sector consists of the supply part, the demand part, and the
choice part. The capacity of parking supply depends on the parking spaces
being provided and the average lengths of stay. In this study, parking
spaces in a CBD area include: (1) curb parking, (2) off-street parking
garages operated by the government, (3) off-street parking garages operated
by private companies, and (4) off-street parking required around or at the
basement of buildings. The curb parking spaces may be constrained by
parking prohibition or restricted parking period. In addition, the effi-
ciency of parking management affects the availability of effective parking
spaces. The off-street parking required at each building may be illegally
used for other purposes, which will force the designated users to use curb
parking instead. For the off-street parking operated by either the govern-
ment or. the private firms, the space increases with the rate of new parking
garage construction and decreases with poor maintenance.
Parking demand is defined as the accumulation of vehicle parked at a given
time as a result of activities at a given site. These may be maximum accu-
mulations during the average day of the week, or during the peak season of
the year. Irrespective of when they occur, parking accumulations result
from interactions between three traffic variables: the total daily trips
attracted, the time pattern of arrivals, and the average lengths of stay
(Witheford 1972). In this study we are more interested in the parking
demand during the peak period in CBD. Thus, the CBD automobile trips gene-
rated from the modal split sector are translated into the CBD peak parking
demand according to an assumed pattern of arrivals and the lengths of stay
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in the study area.
To simplify matters, auto trip makers are given two choices, either park in
an off-street garage or park on the streets. The choice is made according
to the costs spent for parking and the parker's socioeconomic characteristics.
The costs spent for parking consist of the monetary costs of parking, the
time spent for searching a parking space, and the walking time from the park-
ing lot to the final destination. The monetary costs for parking include not
only the parking charges but also the average fine for illegal parking. When
parking violation enforcement is enhanced, the costs of CBD curb parking in-
crease, which lowers the utility of curb parking. The time spent for search-
ing a parking space increases as the availability of parking spaces, which is
represented by the reciprocal of the demand to supply ratio, decreases.
Traffic/Parking Interaction Sector
Streets in cities are used as a facility to provide spaces for moving and
storing vehicles. Since road area in the city is limited, the sharing count-
erparts compete with each other when their demands exceed a certain level.
In the model, the CBD road area is divided into road area for traffic and
road area for parking according to a certain allocation ratio. The ratio
is usually adjusted by the current level of traffic demand. Thus, when the
traffic volume increases to a certain level, curb parking supply usually
decreases due to the elimination of curb parking spaces or the shortening of
the allowable parking period. Curb parking influences road traffic not only
for the narrowing streets, but also for the disturbance of illegal parkings
which either block the sight distance at the intersections or interrupt the
traffic flow when parallel parking is undertaken. In the city of Kaohsiung,
many parkers used to park their cars perpendicular to the curb, which furth-
er reduces the available road area for traffic.
Financial Management Sector
The model attempts to develop causal links between the revenue sources and
expenses of the parking system. The revenue sources consist of (1) the
parking fee revenues, which increase with the volume of parking, both curb
parking and the off-street parking operated by the government, and the ave-
rage parking fee being charged, (2) the parking violation fine revenues,
which increase with the number of parking violation and the amount of fine,
(3) the off-street parking supply uncomplying fine revenues, which increase
with the amount of fine and the number of required off-street parking spaces
being illegally changed to other usages, and (4) the tax revenues collected
from the privately owned parking garages, which increase with the tax rate
and the amount of parking spaces.
The collected revenues, coupled with government aids, are the source of the
budget for (1) the construction of new parking garages in CBD, (2) the inst-
allation of curb parking meters, (3) the operations and maintenance of the
existing parking facilities, (4) the capital investment in parking enforce-
ment facilities, (5) the management for the control of illegal usage of the
required off-street parking spaces, and (6) other parking related traffic
control and management.
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POLICY ANALYSIS
There are two major concepts of parking management. In one concept, parking
management strategies are designed to provide adequate spaces for vehicles.
In the other, parking strategies are employed to limit traffic in the CBD
area (Parker 1980). From a unified systems management point of view, park-
ing management strategy is a measure taken to alter the supply, operation,
and/or parking demand of an area's parking system to facilitate the attain-
ment of local transportation, economic, environmental, and other objectives
(Direnzo 1979). Thus, it is inappropriate to adopt any one concept for a
given area as the choice of a parking policy.
In this study, parking management strategies are grouped by various parking
related problems. The potential parking management strategies are selected
according to the associated problems and then tested to examine their effect-
iveness in the system. The following sections discuss these potential park-
ing management strategies, the conditions under which they may be applied,
and the associated model parameters need to be changed.
As mentioned previously, over 97 per cent of the curb parking spaces in the
city of Kaohsiung are provided free. If this privilege continues, and judg-
ing from the growth trend of auto ownership in Kaohsiung, one may easily
foresee a sharp increase in automobile trips in the near future. The instal-
lation of parking meters will increase the cost of curb parking and lower the
utility of automobile trip-making. In the model, the strategy is played by
adding the parking meter fee to the monetary cost of curb parking. The out-
put of simulation shows that some of the trips shift to transit and some of
the curb parkers switch to off-street parking. As a result, parking revenues
are increased. In practice, the installation can be done by stages according
to the demand to supply ratio in the system. In addition, parking surcharges
can be conducted in congested areas.
In some of the congested areas, elimination of curb parking is a commonly
used strategy to increase the road area for traffic. In this model, the
elimination is performed through raising the ratio of the CBD road area for
traffic. The elimination can also be conducted for the peak periods by
shortening the allowable parking time. The increased hardship on parking in
CBD will reduce the utility of curb parking and consequently the utility of
CBD automobile trips, hence the attractiveness of the CBD area is reduced.
In the mean time, however, the increased road area for the traffic raises the
utility of auto trips and attracts more auto trips to the CBD area, if other
parking spaces, such as off-street parking, are available. In the simulation
the demand of off-street parking increases rapidly which results in an incr-
eases of the tax revenues from the privately owned garages and the parking fee
revenues from the government operated garages. Since the consequence of
increasing auto trips hinders the attainment of the proclaimed goals of
energy conservation, environmental protection, and transportation efficiency,
various strategies aimed at discouraging the auto travel, especially those
single-occupancy-auto trips, are played as supporting actions to this stra-
tegy. These actions include establishing reserved parking for high-occupancy
vehicles, raising all parking fees, increasing the parking costs for single-
occupancy vehicles, carpooling and vanpooling programs, and other measures
which improve the level of service of the transit system.
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The survey conducted by the authors reveals the high percentage of illegal
curb parking as well as the weakness of the parking regulation enforcement.
The power of strict parking regulation enforcement patrol can be strengthen-
ed by increasing the budget for necessary manpower and equipment as well as
by raising the amount of fine for parking violations. The increased revenues
from parking violation fine serve as an important source of funds for improv-
ing enforcement patrol which reduces the number of illegal parking. However,
the reduced number of illegal parkings will soon result in decreasing inflows
from parking fine revenues. A complementary budget for parking violation
enforcement should therefore be maintained.
Many of the traffic congestions during peak periods are largely caused by
automobile work trips. A study by Shoup and Pickrell (Shoup 1980) shows that
some of the pricing strategies designed to discourage the use of automobiles
to CBD area have failed due to the parking subsidy from the employers. The
strategies of short-term parking and late opening of parking are designed to
reduce the available parking supply to the auto commuters. When implementing
these strategies, transit service improvements or park and ride facilities
along transit routes should be the supporting actions. For the retailing
business, since most of the shopping trips occur during off-peak periods with
short-term parking, these strategies lead to more efficient utilization of
parking spaces.
Despite the raising costs of operation, high parking charges, and various
transportation disincentives, all indications are that travel by private
automobiles will continue to dominate transportation at least in the next
two decades (USDOT 1976). To cope with this fact, the provision of proper
amount of off~street parking spaces is still a necessity. In this model,
revenues can be collected from various sources as discussed in the financial
management sector. They are then contributed to a special parking fund which
is then allocated to various usages, including the investment capital needed
for the construction of multilevel parking garages. In the simulation, an
appropriate allocation policy which matches revenues with the expenses of the
system can be determined by trial and error method. The site of the new
parking garages should be selected to meet the future parking demand.
The simulation model is designed in such a way that future scenarios can be
generated for policy experimentation. For example: (1) an increase in urban
population growth rate, which can be performed by raising the population
growth factor in the model, (2) an increase of the level of income in Kao-
hsiung, which can be done directly by raising the income level in the model,
and (3) the construction of a rail rapid transit system (the plan has already
been proposed this year), which can be conducted through raising the utility
of the transit system by a larger scale. However, owing to the very limited
computer budget. for this study, only the base case conditions are simulated.
CONCLUSION
In this paper, various parking management strategies are analyzed and tested,
and their results are evaluated. Due to the difficulty in data collection
and the relative limited experience about the causal relationships developed
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in this study, the model is still far from complete and meant to be illustra-
tive rather than conclusive. Nevertheless, the causal structure established
in this study does provide us a clear understanding about the complicated be-
haviors in the parking management system, which opens a door for further stu-
dies in this area.
REFERENCES
DiRenzo, John F., Bart Cima and Edward Barker, Study of Parking Management
Tactics, Volume 1: Overview, report prepared for the U.S. Department of
Transportation, Washington, D.C., 1979.
Kaohsiung City Government, Department of Information, Kaohsiung, A Big
Industrial and Commercial Port City, Kaohsiung, Taiwan, Republic of China,
May 1984,
Parker, Martin R,, Jr. and Michael J. Demetsky, Evaluation of Parking Mana-
gement Strategies for Urban Areas, Virginia Highway & Transportation Re-
search Council, Charlottesville, Virginia, 1980.
Shoup, Donald C. and Don H. Pickrell, Free Parking as a Transportation
Problem, Final Report prepared for the U.S. Department of Transportation,
Washington, D.C., 1980.
Witheford, David K. and George E. Kanaan, Zoning, Parking, and Traffic, ENO
Foundation for Transportation, Saugatuck, Connecticut, 1972.
USDOT, Federal Highway Administration, Traffic Control Systems Handbook,
Washington, D.C., 1976.
