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Examining the Impacts of Self-selection on Household Vehicle Type Choice: Case Study of Tehran

Mohammadi, Ali | 2021

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 54382 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Kermanshah, Mohammad
  7. Abstract:
  8. There is a specific focus in sustainable transportation to three domains of safety, air pollution, and energy consumption. All these three domains are affected by the vehicle type choice. An important factor to estimate the impact of vehicle type choice on safety, air pollution, and the energy consumption is self-selection, defined as the tendency of people to make their travel-related choices based on their abilities, needs, and preferences. Ignoring the self-selection effect may cause a bias in the estimation of the coefficients of affecting variables on the travel-related choice. The main objective of this thesis is to study the self-selection effect in vehicle type choice considering the simultaneous effects of both objective and subjective variables.In this study, three data banks are merged. The first data bank includes the objective and subjective data of Tehranian people owning a vehicle. To build this data bank, a survey is designed, and 731 complete questionnaires are collected with face-to-face interviews. The second data bank includes the land-use information of Tehran city used to determine the built-environment characteristics of the residential location of interviewees. The third data bank includes the characteristics and features of vehicles owned by interviewees and collected from the official websites of the vehicle manufacturers. Based on vehicle weight and features, seven categories of vehicles are defined, named as mini, compact, medium, large, SUV, pickup, and motorcycle. To analyze the self-selection effect, a two-step procedure was employed. In the first step, the latent subjective variables are extracted using factor analysis. In the second step, the impacts of both objective and subjective affecting variables on vehicle type choice are identified using discrete choice modeling.The results of this study show that both subjective variables (like attitudes, personality, lifestyle, and satisfaction) and objective variables (like socio-demographics and built environment characteristics) have significant effects on vehicle type choice. Built environment characteristics such as population density and job density were found to be more effective compared to residential location attitudes. Moreover, the study suggests that the income level of individuals has a considerable effect on their vehicle type choice, with the exception of pickup owners. It was found in the study that the pickup vehicles are more likely to be chosen by lower educated individuals (i.e., with a degree of diploma or lower) with the main purpose of working with their vehicle. In addition, it was found that the pickup vehicle choice would severely change by varying the individuals’ attitudes toward the safety of motorcycles.Another finding of this study is about the considerable impacts of individuals’ attitudes toward safety on vehicle type choice. These variables are found to be significant in utility functions of various vehicle types. Moreover, they have a distinguishing effect in clustering individuals based on subjective variables. Sensitivity analyses are run by creating crosstabs based on the effect of objective and subjective variables on vehicle type choice. The findings show that the probability of choosing large vehicles is increasing about 15% between higher-income individuals by varying their subjective variables
  9. Keywords:
  10. Attitudes ; Latent Variable ; Built Environment ; Statistical Control ; Subjective Variable ; Lifestyle ; Vehicle Type ; Self-Selection Effect ; Sustainable Transportation

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