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Examining Potential Demand of Public Transit for Commuting Trips. Xiaobai Yao Department of Geography University of Georgia, USA 5 July 2006. Outline. The trend of public transit in the US Objectives of the study Methodology Case study Conclusions.
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Examining Potential Demand of Public Transit for Commuting Trips Xiaobai Yao Department of Geography University of Georgia, USA 5 July 2006
Outline • The trend of public transit in the US • Objectives of the study • Methodology • Case study • Conclusions
Renaissance of Public Transit in the US • Traffic congestion • Economic growth • Gas price vs affordable transit fare • Environment sustainability
Research on Public Transportation • Accessibility for special groups • Land use / transportation relationship • Cost, benefit, pricing • Network analysis • …?
Research objectives of the study • Measure the potential need of public transportation • Identify and visualize clusters of high potential needs areas
Methodology • Identify Predictive Factors • Identifying and Visualizing Potential Demand Distribution • The Need Index approach • A data mining approach • Case study
Data Land-use, socioeconomic, and transportation (trips by mode) data at TAZ level.
Identify Predictive Factors Multiple Regression where R is the proportion of workers taking public transit as the primary mode, vi ’s are the identified independent variables, and k is the total number of these variables.
Identify Predictive Factors- the Atlanta case Independent variables: • Land-use characteristics • Population density - Average number of workers per HH • Employment rate - Job density • Percentage of home workers • Socioeconomic characteristics • Income - Car ownership • Network structure • Density of bus stops in the TAZ - Density of rail stations in TAZ
Identifying and Visualizing Potential Demand Distribution • The Need Index approach • A data mining approach – self-organizing maps
1. The Need Index approach yi ’s: variables accounting for the network structure and level of service of transit systems xi ’s: variables that are not about the transit systems. R = NI + Net NI = R-Net
Simple calculation Easy interpretation Possible to rank and/or to quantify the difference Classification/Visualization Dilemma (where are the magic breaks) The validity of linear relationship assumption Critique on the Need-Index approach
2. The SDM approach : Self-organizing maps <x1, x2, …. xn>
No assumption on the relationship Self-assigned clusters No quantitative measure No ranking Critiques on the SOM approach
Conclusions • The integrative approach is successful. • The Need Index approach and the spatial data mining approach are complementary and mutually confirmative. • Confirmed by the other approach, the Need Index approach provides an efficient and effective solution to transportation planners.