GIS based destination accessibility via public transit and walking in Auckland, New Zealand Suzanne Mavoa a,⇑ , Karen Witten a , Tim McCreanor b , David O’Sullivan c a SHORE, School of Public Health, Massey University, PO Box 6137, Wellesley Street, Auckland 1141, New Zealand b Whariki, School of Public Health, Massey University, PO Box 6137, Wellesley Street, Auckland 1141, New Zealand c School of the Environment, University of Auckland, Private Bag 92019, Auckland, New Zealand article info Keywords: Accessibility GIS Public transit Walking Transport abstract There is relatively little research on accessibility using public transit as the travel mode. Yet understand- ing public transit accessibility is important for encouraging mode shifts to reduce car reliance and is essential for the wellbeing of non-car households. The paper describes two measures of public transit access. The first is a combined public transit and walking accessibility index, which measures potential access to destinations via public transit and walking modes. The second is a transit frequency measure, which is a measure of transit service level in an area. These two measures extend current public transit accessibility measures by including all components of the public transit journey, calculating accessibility at the parcel level and providing a measure of public transit service. Results for the Auckland region show that although 94.4% of the urban population live in areas with medium–high public transit and walking access, only 26.5% of the urban population also have an average transit frequency of two or more trips per hour per stop. Moreover, only 5% of the urban population live in areas with an average transit frequency of more than four services per hour per stop. This work highlights the importance of including measures of transit frequency when investigating public transit access. The results also reveal the potential to use these measures to gain a more complete and realistic picture of public transit access and to explore the potential for mode substitution and accessibility for non-car households. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction A considerable body of research seeks to develop models and measures of accessibility, which has been defined as ‘‘the ease with which activities at one place may be reached from another via a particular travel model’’ (Liu and Zhu, 2004, p. 105). However there is relatively little research on accessibility using public transit as the travel mode. Martin et al. (2002) suggest that this has been due to lack of availability of public transit data and the more sophisticated modeling required due to the complexity of the jour- neys that can be undertaken by public transit. Yet, accessibility by public transit modes is becoming increas- ingly important for two reasons. First, high levels of car travel and car dependence can have detrimental effects on both our phys- ical health and the environment (Litman, 2003; Shannon et al., 2006). Increasing Green House Gas (GHG) emissions (Litman, 2003), traffic congestion (Litman, 1999), traffic accidents (Litman, 2003), oil price vulnerability, and physical inactivity and obesity related disorders (Sallis et al., 2004) have all been associated with increasing levels of car use. Reducing car travel to mitigate these negative effects is unlikely unless the destinations of daily life can be readily accessed via other transport modes. Thus it is impor- tant to understand whether destinations are accessible using pub- lic transit. A second reason for the importance of public transit accessibil- ity relates to equity issues. Regardless of the success of policies to reduce car travel and car dependence, there has always been, and will likely continue to be a segment of the population who do not have access to a private car and are reliant on public transit (Martin et al., 2008). The relative vulnerability of the public transit-reliant population – youth, elderly, marginalized – is the reason that Martin et al. (2008) have called for more attention to be paid to the incorporation of public transit into accessibility modeling. In this research we are interested in the destinations that are accessible when people are restricted to public transit and walking modes of travel. We have addressed this question by creating a measure of public transit and walking access to a range of destina- tions that represent places that people travel to in everyday life. This paper reviews literature on measures of public transit accessi- bility, describes the calculation of a Public Transport and Walking 0966-6923/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.jtrangeo.2011.10.001 ⇑ Corresponding author. Address: SHORE, SHORE and Whariki Research Centre, School of Public Health, Massey University, PO Box 6137, Wellesley Street, Auckland 1141, New Zealand. Tel.: +64 9 3666136; fax: +64 9 3665149. E-mail address: s.mavoa@massey.ac.nz (S. Mavoa). Journal of Transport Geography 20 (2012) 15–22 Contents lists available at SciVerse ScienceDirect Journal of Transport Geography journal homepage: www.elsevier.com/locate/jtrangeo