Background
Although evaluating access to public transport has been of particular interest in the urban planning literature, many questions remain about travelers’ choice of transit mode. First, while previous research has studied the effects of the built environment on transit use focusing on how riders choose their access modes on the basis of transit-onboard surveys, few examined potential riders’ travel behavior. Those based solely on data describing rider’s choice have been mainly concerned with how riders choose their access modes, once riders decide to take transit; consequently those literature rarely have accounted for the role of the built environment in promoting choice of taking transit. Most importantly, few studies have examined the effect of perceptions of walking access on transit use. Filling the gaps in the literature, this paper pays particular attention to residents’ perceptions of their walking environments such as security concerns, along with objectively assessed neighborhood characteristics, using both riders and non-riders’ travel data of Los Angeles County.

Objectives
The overall aim of this study is to determine what types of land use policy produce a higher reliance on public transportation. My analysis examines how neighborhood characteristics affect the traveler’s propensity to use public transportation, with particular emphasis on the roles of perceptions of the walking environment near stations. To this end, the study examines 4598 travelers of Los Angeles County as described in the 2009 National Household Travel Survey (NHTS)-California sample. I apply theories of travel behavior to analyze environmental constraints on a usual behavior with regard to transit use.

Methods
I expect the perception variables are strong modifiers that directly influence their travel behavior and these are important to control individual travel-related attitudes and individual selection of a neighborhood type. Perceptions of walking environment include physical safety from traffic, personal safety from street crime, and recognition of lack of accessible destinations and paths. Personal perception and attitudinal variables come from 2009 NHTS-California sample. Exploratory factor analyses with a varimax rotation are also employed to ascertain neighborhood types, using census files and the Southern California Association of Government’s network and land-use dataset for the year 2008. Neighborhood types are measured in continuous dimensions that are combinations of important urban form features associated with auto dependency. Finally, ordinary logit model estimates the odds of being a regular transit user relative to an occasional or not-user, and it examines how the effect of perceptions vary neighborhood types, controlling individual socio-demographic characteristics of travelers.

Results
Several neighborhood-specific characteristics show influences over propensity to use public transportation, after controlling individual socio-demographic variables. Consistent with previous research, the results of this study show if respondents live in a highly dense urban area characterized by mixed land-use and multifamily housings, they are more likely to be regular transit users. However, the roles of mixed land-use and density are limited. Many residential areas characterized by low highway and transit accessibility, though they have mixed land-use patterns, nonetheless favor auto commuting and appear to be less dependent on public transportation. It indicates that traditional neighborhood design characteristics of dense, mixed land-use patterns and high accessibility of transportation network system together have the potential to promote transit use rather than independently.

Furthermore, the results of this study suggest that individual’s perceptions regarding safety and accessible destinations have a significant influence on determining propensity to use public transportation. It implies that individual perceptions may be a more direct modifier which limits the practical range of an individual travel choice. More interestingly, the spatial variations are also found in the relationship between individual's perceptions and their transit use. Urban multifamily housing zones characterized by attached units and mid-income households are the places where the resident's great sensitivity on the physical safety has a positive influence on the number of transit trips. This interaction term supports empirical evidence and theoretical expectations that the compact urban form can promote transit use. However, this potential is limited geographically, because as observed in employment centers and urban clusters, many dense employment environments are not sensitive to this interaction term. This is only effective when socioeconomic and individual perception aspects of the neighborhood are considered simultaneously.

Conclusions
This suggests that, in order to increase the reliance on public transportation, land-use-related policy should be adopted locally based on each individual geographical context.

Support/Funding
School of Policy, Planning and Development, University of Southern California.