A System Dynamic Model for Coordinated Planning of Bus Rapid Transit and Transit Oriented Development
Lan WU1,2, Ruey Long CHEU3, Xuewu CHEN1, and Luis David GALICIA4
1Transportation College, Southeast University, Nanjing, 210008, China Lan Wu: [email protected], Tel: +86-25-85427611, Fax: +86-25-83794102
2College of Auto and Traffic Engineering, Nanjing Forestry University, Nanjing, 210037, China Xuewu Chen: [email protected], Tel: +86-25-83795643, Fax: +86-25-83794102
3Dept. of Civil Engineering, The University of Texas at El Paso, 79968, Texas, USA; [email protected]. Ruey Long Cheu: [email protected], Tel: +1-915-747-5717, Fax: +1-915-747-8037
4Dept. of Civil Engineering, The University of Texas at El Paso, 79968, Texas, USA David Galicia: [email protected], Tel: +1-915-747-8737, Fax: +1-915-747-8037
ABSTRACT
Bus Rapid Transit (BRT) has been increasingly regarded as a cost-effective mode of transportation. In order for BRT ridership to be sustainable, the planning of BRT stations must be coordinated with transit oriented development (TOD). Yet, no tool exists for planners to systematically model the BRT system with TOD. This paper proposes three stages of TOD (incubation, rapid growth, and maturity) that mirror the three BRT deployment phases (limited, moderate, and aggressive). The system dynamic (SD) approach has been suggested to model the progress of TOD and BRT deployment over time. The SD model consists of three modules: population, BRT, and TOD. The population and BRT modules have been developed and are described in this paper.
INTRODUCTION China has the largest population in the world, and the population density in
large and medium cities is higher than that of most cities in other countries. This high population density benefits the development of public transportation, which will then promote the savings in energy and the protection of the environment. The State Council Office (2005) of China has explicitly indicated that prioritizing public transport development is an essential measure to improve the operating efficiency of transportation resources and reduce urban traffic congestion.
In 1987, the United Nation published a special report, “Our Common Future” (United Nations, 1987), in which the concept of “sustainable development” was proposed for the first time. Sustainable development of urban transportation requires the coordinated development of urban land use and transportation and a
model of urban land development including space expansion facilitated by public transit. Calthorpe (1995) proposed the concept of transit oriented development (TOD), which has received popular support among urban planning and transportation professionals.
In general, the “T” in TOD refers to the following transit modes: Mass Rapid Transit (MRT), Light Rail Transit (LRT), and Bus Rapid Transit (BRT). Since BRT has the advantage of relatively small initial investment and short implementation period compared to MRT and LRT, more and more cities are considering BRT as the transit mode in support of TOD.
The term TOD refers to mixed use, relatively intense development concentrating around a transit station in a ¼- to ½-mile radius and oriented to transit riders with a pedestrian- and cycle-friendly environment (Zhang, 1987). Among the benefits of TOD are increased market activities and land/property value along the transit corridor. Additionally, TOD increases commercial activities and can reduce maintenance cost for the entire system. Some transit agencies have developed the land surrounding the stations and sold it for profit to finance the construction of the transit line. Examples of increases in land value are (1) Brisbane, Australia, where the land value increased by around 20 percent along the BRT corridor; (2) Bogotá, Colombia, and Washington, D.C., which reported an increase in apartment rentals along their BRT projects; and (3) San Francisco-Bay Area Metro, with a $1,578 USD premium for every 0.2 mile closer a home is from a BRT station (Wright 2004).
Transfer facilities may also generate market activities in the neighborhood. Intermodal and transfer facilities permit integration with other type of services. This expands the BRT service area and consequently potential ridership (Kim et al., 2005).
BRT systems have been successfully implemented in cities such as Curitiba (Brazil), Bogotá (Columbia), Miami (U.S.), Vancouver (Canada) and Sidney (Australia). Owing to the successful implementations worldwide, many cities in China have developed BRT systems. Beijing, Hangzhou, Kunming, Changzhou, Dalian, Chongqi, Tianjin, Suzhou, and Jinan are cities that already have operational BRT systems; Guangzhou, Shamen, and Shanghai are in different stages of construction, and Shenzhen, Zhenzhou, Hefei, Wuhan, and Tai’an are developing their respective BRT plans.
Compared to the relatively shorter implementation time frame of a BRT system, TOD requires years or decades to complete. A comprehensive TOD plan may consist of several stages. For simplicity, this paper defines the TOD in three stages: incubation, rapid growth, and maturity. In the different stages, the transportation demand and supply possess different characteristics and interact with the TOD features. Galicia et al. (2009) presented three BRT deployment phases: limited, moderate, and aggressive. These three phases may not coincide with the three stages of TOD. However, the progressive deployment of BRT features has positive impacts on the TOD stage of development, and vice versa. This paper
proposes the system dynamic (SD) approach to model the BRT and TOD features and their interaction over time.
TRANSIT ORIENTED DEVELOPMENT
Calthorpe (1995) suggested that the minimal residential density of TOD is 10 households/acre. The average population density for TOD, as he suggested, is 13,500 persons/km2. Statistics in U.S. has shown linkages between residential density and transit use. Pushkarev and Zupan (1977) found that residential density of 2 to 7 households/acre (5 to 17 households/hectare) was of marginal value in providing transit service. If the residential density is in the range of 7 to 30 households/acre (17 to 74 households /hectare), transit effects was notable. When the residential density increases from 7 households/acre (17 households/hectare) to 30 households/acre (74 households/hectare), transit demands triple and, at the same time car usage, declines.
While the higher population density of TOD has a positive impact on transit trips, TOD reduces the number of trips a passenger makes per day. This is a result of the alternatives the user has to get products and services inside the system without commuting outside the system (GTZ, 2006). On the other hand, TOD may attract additional vehicle trips from outside the transit corridor due to the commercial establishments around the transit stations (Zhang, 2007). The impact of TOD on BRT ridership and vehicle-based trips is complex. STAGES OF TRANSIT ORIENTED DEVELOPMENT
A TOD community is dynamic, and its emergence and growth are an evolving process. However, TOD has to be carefully planned. Based on an analysis of successful experience of TOD community development internationally, this paper divides TOD community evolution into three stages. Stage one: Incubation
This stage is subdivided into the planning phase and programming phase. In the planning phase, a government agency takes the lead to coordinate with other agencies to develop a TOD plan that will meet the sustainable goals of the community, city, or region. The TOD plan should be coordinated with the urban master plan, land use/zoning, and transit network. The draft TOD plan should be available for the public to comment and revised to incorporate feedback from the stakeholders. Meanwhile, the responsible government agencies should establish zoning policies to encourage high density land development around BRT stations. In the programming phase, the BRT stations and parcels around the transit stations should be given priority in project scheduling and fund allocation. The BRT stations, guideways, and other infrastructure feature are the first to be constructed. The construction of mixed use facilities should start with the BRT stations and gradually expand from the
stations. Attention should be paid to the intermodal connections and pedestrian and bicycle amenities (Zhang, 2007). Stage two: Rapid growth
When the construction of BRT station and the surrounding commercial/residential facilities has been completed, the responsible government agency should encourage private enterprises to establish businesses in the TOD neighborhood. A potentially effective policy is to provide tax incentives for residents and businesses located within a TOD. Government offices should also be encouraged to be located within a TOD. Once users realize the convenience of transit and mixed use facilities, the population density, spatial dimension, and transit ridership will grow rapidly. The high density activity pattern with BRT stations as its core start to form, connected by the BRT line along its route.
Stage three: Maturity
As the commercial and residential occupancies in the TOD continue to increase, the BRT system is expected have increasing ridership. However, at some point, the commercial and residential land uses will approach their respective maximum planned density. At this point, the grow rate, although still positive, will start to decline. At this maturity stage, the BRT system is said to carry the maximum ridership generated by the TOD community. The fully developed BRT system should be designed to carry this demand. At maturity, the spatial dimension of TOD reaches its planned limit. Land development has been completed. At the same time, the growth rate of residents and employees has also declined, and TOD population density approaches saturation condition, with commuting passengers reaching the maximum.
PHASES OF BRT SYSTEM DEPLOYMENT
Galicia et al. (2009) has proposed three phases of BRT deployment along a corridor: limited, moderate, and aggressive phases. The three phases offer increasing orders of infrastructure and operational amenities. The limited phase is for a relatively low budget and quick implementation, while the aggressive phase is for a full scale BRT system with exclusive rights-of-way and customized stations, but also is more costly and takes a longer time to develop. Galicia et al. suggested that a BRT system does not need to be implemented in order of the three phases. A planner may decide to skip a phase or start with the moderate or aggressive phase if budget and time permit. For the purpose of this paper, and in order to model the evolution of a BRT system along with TOD, the three phases of the BRT deployment are kept.
Very often, the first stage or deployment phase of a BRT corridor is simply an enhancement of the existing regular bus route. The basic features in a limited phase could include some form of bus priority signal, onboard fare collection, improved shelters, clean vehicle technology, and marketing identity (Wright, 2004). Financially and technically speaking, this deployment phase consists of a set of low-cost features that are relatively easy to put into operation. Moderate phase This phase includes more advanced features such as segregated busways, pre-board fare collection/verification, higher quality shelters, level access platforms, clean vehicle technology, and marketing identity. These features further reduce travel time and improve ridership attraction.
Aggressive phase
The main characteristics that distinguish this phase are metro/subway-quality service, an integrated network of routes and corridors, weather-protected/high quality stations, pre-board fare collection/verification, high frequency and rapid service, modern and clean vehicles, marketing identity, and superior customer service. Wright (2004) stated that there were only two truly full BRT systems in the world: Bogotá and Curitiba.
INTEGRATED MODELING
In view of TOD development stages and characteristics, the deployment of BRT coordinated with TOD development may be arranged according to the following figure. Although there are three phases of BRT deployment and three stages of TOD, are shown coupled in Figure 1, the timing of the three BRT phases and the three TOD stages do not necessarily coincide.
Figure 1. TOD stages and BRT deployment phases
This paper proposes to use the SD approach to model the coordinated
development of BRT and TOD over time. The coordinated model could serve as a decision support tool that enables urban planners and transportation planners to make decisions on the scale and timing of both BRT and TOD developments. The following section describes the SD approach. Galicia and Cheu (2010) have developed a SD model for BRT corridor ridership estimation, using BRT features to represent the three deployment phases as inputs. This model will be described in the subsequent section.
SYSTEM DYNAMICS MODEL System dynamics is a modeling approach for users to perform simulation of
dynamic systems that involve many interlocking variables with feedback loops. In SD models, variables and their relationships are represented graphically by the so-called casual loop diagrams. The relationship between two variables may be described by an equation, or heuristic (if-then rule). Once a model has been constructed, users can simulate the effect of the change of one or more variables on the entire system over time. System dynamics has been used as a tool to study organization behavior due to policy changes (Sterman, 2000). The SD approach has been applied to model land use policy (Pena and Fuentes, 2007) and land use and transportation interactions (Hagani et al., 2003a, 2003b; Wang et al., 2008). Applying the SD approach to model the interaction between TOD and BRT is a natural extension of the applications.
A SD model for BRT ridership estimation has been presented by Galicia and Cheu (2010). The new model proposed in this paper aims to capture the system behavior (e.g., population, ridership, commercial activities, etc.) along a BRT corridor that consists of planned TOD around the stations. Using the experience gained in the development of the SD model presented in Galicia and Cheu (2010), the new SD model consists of three modules: population, BRT, and TOD. Each module has a group of distinct variables interacting with one another. The three modules interact with one another through the cross-module connections between selected variables. From past experience in SD modeling, the population (within a ¼ and ½ mile around the stations) is the most important variable that drives the BRT system and possibly TOD. The BRT ridership is affected by the TOD and, in return, the BRT’s infrastructure and operational features influence the TOD. The TOD, in turn, provides feedback that changes the population along the corridor. Figure 2 depicts the overall interactions in macroscopic view between the three modules.
The population module and the BRT module, and the interactions between
them, have been developed and presented by Galicia and Cheu (2010) using VENSIM (Ventana, 2008), a SD modeling software. The loop diagram of the two modules is as shown in Figure 3. The top part of the figure is the population module in which the population along the corridor over time (within ¼ or ½ mile radius from BRT stations) is estimated with a base year population, birth rate, death rate, and net migration rate. The estimated corridor population, multiplied by the BRT mode share, produces the potential daily ridership. The seven BRT features, as shown in the bottom left corner of Figure 3, combine to attract additional ridership. The bottom right corner of Figure 3 describes the interaction of BRT operational features along the corridor.
The SD model in Figure 3 has been applied to the planned BRT corridor along Mesa St. in El Paso, Texas. Three deployment scenarios, namely limited, moderate, and aggressive phases, have been assumed to take place in 2007, the initial year. The simulation was performed annually up to 2035. Figure 4 shows the total corridor monthly ridership (converted from the total daily ridership) from 2007 to 2035 for the three deployment scenarios.
VENSIM permits modelers to customize the user interface so that regular users do not need to be concerned about the details of the casual relationships between the variables. The modeler can develop a user friendly graphical interface such as the one shown in Figure 5. In Figure 5, the top left corner consists of five slide bars and text boxes for the user to input the variables of interest. The top right corner shows the total corridor ridership estimates, which is the same as in Figure 4. The bottom half of Figure 5 displays the fleet size and operating headway. Note that the fleet size and headway, in integers, are adjusted to serve the estimated number of riders.
Figure 5. Graphical user interface of system dynamics model
SUMMARY AND FUTURE WORK This paper has proposed three stages of TOD development (incubation, rapid
growth, and maturity) that mirrored the three BRT deployment phases (limited, moderate, and aggressive). The SD approach has been proposed to model the coordinated development of the BRT corridor and the TOD around the stations. The SD model consists of three modules: population, BRT, and TOD modules. The population and BRT modules have been developed and described in this paper. The current work and future work include the development of the TOD module and
connecting it with the population and BRT modules. This includes (i) the identification of the important variables that describe the TOD (within the TOD module and connections with external variables in the population and BRT modules); (ii) coding the relationships between the variables; and (iii) validating the model (either the TOD model or the entire SD model itself) with an actual case. Once developed, the SD model should serve as a decision support tool for planners and transportation engineers in the development of BRT and TOD projects.
REFERENCES Calthorpe, P. (1995). The Next American Metropolis: Ecology, Community, and the
American Dream. Princeton Architectural Press, 3rd Edition. Galicia, L.D., Cheu, R. L., Machemehl, R., and Liu, H. (2009). “Bus rapid transit
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Galicia, L.D., and Cheu, R. L. (2010). “A system dynamics model for bus rapid transit corridor planning and ridership forecasting.“ Proceedings of the 89th Annual Meeting of the Transportation Research Board, DVD.
GTZ (2006). Proceedsings of the 2nd international Conference of Sustainable Transportation. Mexico City. Deutsche Gesellschaft für Technische Zusammenarbeit (GTZ). CD-ROM
Haghani, A., Lee, S. Y., and Byun, J. H. (2003a). “A system dynamics approach to land use/transportation system performance modeling, part I: Methodology.” Journal of Advanced Transportation, 37(1), 1-41.
Haghani, A., Lee, S. Y., and Byun, J. H. (2003b). “A system dynamics approach to land use/transportation system performance modeling, part II: Application.” Journal of Advanced Transportation, 37(1), 43-82.
Kim, E., Darido, G., and Schimek, D. (2005). Las Vegas Metropolitan Area Express (MAX). Report FTA-VA-26-7222-2005.2, Booz Allen Hamilton, Inc.
Pena, S., and Fuentes, C. F. (2007). “Land use changes in Ciudad Huarez, Chihuahua: A systems dynamic model.” Estudios Fronterizos, 8(16), 65-89.
Pushkarev, B.S., and Zupan, J.M. (1977). Public Transportation and Land Use Policy. Indiana University Press.
Sterman, J. D. (2000). Business Dynamics-System Thinking and Modeling for a Complex World. McGraw-Hill/Irwin.
The State Council Office (2005). Strategies of Giving Priority to Urban Public Transportation Development. Document No.46, China.
United Nations (1987). Our Common Future. United Nations World Commission on Environment and Development, Oxford University Press.
Ventana Systems, Inc. (2008). VENSIM Version 5 User’s Guide. Wang, J., Lu, H., and Pei, X. (2008). “A system dynamics model of urban
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Wright, L. (2004). Bus Rapid Transit Planning Guide. Deutsche Gesellschaft für Technische Zusammenarbeit (GTZ), Division 44 Environment and Infrastructure Sector Project, Transport Policy Advice, Germany.
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