The influence of urban physical form on trip generation, evidence from metropolitan Shiraz, Iran

This paper aims to examine the relationship between urban form and personal daily trips between urban zones across Metropolitan Shiraz, Iran. To cope with collinearity nature of trip generation determinants and also multicollinearity in model estimation, component principal analysis (PCA) was employed to identify latent dimensions of trip generation. Then, a multiple regression model with continuous independent variables was developed to measure the effect of each individual variable on entire trips generated among urban zones. The explanatory variables included both physical characteristics of the metropolitan (land use diversity, density, suburbanization, connectivity, and accessibility to public transport), and socio-economic characteristics of trip makers (age, employment status, education, migration, property value) aggregated on the urban zones scale. The empirical findings, based on ordinary least squares (OLS) estimation of 2006 data for 47 traffic area zones (TAZ) with total population over 1.1 million indicated that socio-economic characteristics were the most positive determinants of trip generation among the zones. On contrast, suburbanization (distance from central business district (CBD)) and distance from public transport facilities were negatively associated with the trip generation. However, other physical factors such as land use mix and network connectivity were found not important in influencing intra-zone trip generation, probably influencing inter-zone trip generation instead. In fact, improving local accessibility may reduce the need to intra-zonal travel, rather may also increase the tendency to travel within the neighborhood area. Keywords: Urban transport, urban planning, trip generation, metropolitan Shiraz, Iran.