Xuwei Chen

A comparison of usefulness of 2D and 3D representations of urban planning

Very little existing literature has addressed the issues of the perceived usefulness of 3D visualizations over 2D and the use of cartographic shadow representations in the planning community. Urban planning has moved toward a 3D, geographic-information-system-centric, and functional decision support framework. This study aims to examine the preferences of urban planning professionals with respect to 2D and 3D visualizations in a case study. The authors built a 3D representation of a proposed building along with the existing urban environment in Queenstown, New Zealand and conducted a usefulness test through a survey and interview. Based on the survey, the study evaluated the degree of task utility perceived in each visualization method, the effect on the mental image, and shadow representation preferences. The findings support the literature that the benefits of using a 2D or 3D model are closely related to the types of planning tasks undertaken. The findings also reveal a complex view of planning activities, suggesting that planners themselves cannot be treated as a single group for research purposes.

Agent-Based Modeling and Evacuation Planning

In evacuation planning, it is advantageous for community leaders to have a thorough understanding of the human and geophysical characteristics of a community, be able to anticipate possible outcomes of different response and evacuation strategies under different situations, inform the general public, and develop a set of evacuation plans accordingly. In order to achieve this goal, evacuation managers in a community can use computer modeling techniques to simulate different ‘what-if’ scenarios, use the results from these simulations to inform the public, and generate different evacuation plans under different circumstances. The complexity associated with evacuation planning in an urban environment requires a computer modeling framework that can incorporate a number of factors into the modeling process. These factors include the nature of the disaster in question, the anticipated human behavioral patterns in the evacuation process, the unique geography and transportation infrastructure in a given area, the population distribution in the area, the population dynamics over different time periods, and the special needs of different population groups, to name a few. Agent-Based Modeling (ABM) provides a general approach that can be used to account for these factors in the modeling and simulation process. In this chapter, the authors provide an overview of agent-based modeling and simulation, illustrate how agent-based modeling and simulation were used in estimating the evacuation time for the Florida Keys, and report some preliminary results in planning a hypothetical route for evacuating the elderly from a nursing home on Galveston Island, Texas, based on network dynamics during an evacuation.

A spatial and temporal analysis of commute pattern changes in Central Texas

The Austin–San Antonio Corridor, which encompasses the Austin metropolitan area and the San Antonio metropolitan area, has experienced a significant increase of commute traffic since 1990. Previous research suggested that the level of traffic congestion in the corridor increased significantly in the past two decades. An analysis of the commute patterns would help better understand the underlying causes of traffic congestion and provide information for urban planning and traffic management. Based on the US Census Transportation Planning Package Part 3 Journey-to-Work data for 1990 and 2000, this study developed a set of GIS-based methods to analyze the spatial and temporal change of commute patterns and commute flows in the Austin–San Antonio Corridor. The analyses revealed communities that experienced a significant increase of commute traffic and identified major travel corridors that carry a high proportion of the traffic in the area. The findings from this study should be particularly useful to public transportation providers seeking information for improving the coordination of rural-to-urban public transportation services.

The Spatial-Temporal Dynamics of China’s Changing Urban Hierarchy (1950–2005)

This paper examines the dynamic spatial and temporal patterns of China’s urban hierarchy from 1950 to 2005. We limit the study to mainland China’s 137 urban agglomerations of 750,000 or more population as of 2005. The paper improves upon a classic approach to measuring shifting ranks within an urban hierarchy by applying advanced spatial analysis techniques. We use a Getis-Ord , a space-time Moran scatter plot, and dynamic LISA paths to examine the regional difference and change for these urban agglomerations. Our study revealed a north-south divide in the changing urban hierarchy of China after 1990. The analysis demonstrated that the spatial and temporal shift of urban dominance in China was closely associated with policy and economic factors. The paper concludes with a discussion of the differences across the six different time periods of change from 1950 to 2005.

Agent-based micro-simulation of staged evacuations

One of the most critical issues for an evacuation is to design an effective evacuation strategy that could lead to the reduction of the total evacuation time. Previous studies demonstrated the advantage of certain staged evacuation strategies over the simultaneous evacuation strategy. This study aims to identify an effective yet feasible evacuation zoning structure for staged evacuation strategies of Galveston Island. The proposed zoning structure attempts to reduce the traffic pressure at the beginning of the IH-45 bridge, the only exit to the mainland. This study employs VISSIM, an agent-based microsimulation software package, to simulate the evacuation process. The sensitivity of the total evacuation time to time intervals between notifications of the staged evacuation is examined. The findings suggest that when an appropriate interval is selected, the staged evacuation using the proposed zoning structure is more effective than a simultaneous evacuation. A longer span between notifications could reduce the evacuation time of the last vehicle, but does not necessarily lead to the reduction of the total evacuation time.

Intercity commute patterns in central Texas

There are highly populated regional corridors that connect multiple cities in different parts of the world. Public transportation is believed to be a good solution to ease traffic congestions in these corridors. To make informed decisions about public transportation planning, we must have a clear picture about commuting patterns in a corridor. Although the study of commute patterns has a long tradition in urban planning, urban geography, and transportation analysis, the examination of intercity commute patterns in urban corridors consisting of multiple cities has received limited attention. This study aims to achieve a better understanding of intercity commute patterns and flows in a five-county study area in Central Texas. We used GIS methods and network analysis procedures to analyze the U.S. 2000 Census Transportation Planning Package (CTPP) Part 3 Journey-to-Work data. Results from the analyses suggest that: (1) most (greater than 97%) of the workers with their homes in the five-county area also worked in the area; (2) the number of people who worked in the five-county area exceeded the number of people who had their homes in the area; and (3) most of the intercity commuting trips were between cities located within the same metropolitan area.

Mapping the Vulnerability to Potential Toxic Substance Releases from Industrial Facilities under Emergency Situations: A Case Study of Galveston, Texas

Abstract This research investigates the spatial variations of vulnerability to toxic substance releases under possible emergency outbreaks in Galveston County, Texas. By identifying the potential risk and measuring the extent of possible impact, we provide useful information for the local government and the public to develop more effective evacuation strategies. Assuming that toxic substance releases occur during a worst-case scenario, we determine the vulnerability based on a combination of five factors at the census block level: (1) population density; (2) the percentage of people under 5 years old and above 65; (3) distance between residence and hazardous sites; (4) road network capacity; (5) density of hazardous sites. We employ the Areal Locations of Hazardous Atmospheres (ALOHA) dispersion model to define the impact areas. We calculate an index for each of the five factors. We weigh the indices equally and generate the overall vulnerability index. Results are visualized in a GIS environment.