Figure 1

Comparison of buffer methods for assessing neighbourhood land use for dense and suburban road networks. The circular buffer method includes all land up to 1 km from the individual "as the crow flies" ('circular method', dark gray). This buffer fails to account for how the existing road network restricts the manner in which an individual is able to traverse the landscape. The other two approaches both consider how the road network restricts travel, affecting what is actually accessible within 1 km of travel. The polygon-based network buffer ('polygon method', red) uses the end points of 1 km journeys in the network as the vertices with which to construct an irregular polygon to define the accessible "neighbourhood". The method presented in this paper defines the 1 km neighbourhood by applying a 50 m buffer to a 950 m line-based network buffer ('buffered line method', blue), thus more closely approximating the roads accessible to the individual. The difference between the methods is related to the street pattern. For grid road networks (high connectivity) (A), the difference between the circular method and the network-based methods is moderate with the latter offering only slight improvements in the representation of a "local neighbourhood". However, for irregular road networks (lower connectivity) in suburban settings (B), two important changes are observed. Firstly, the circular method becomes a much less useful approximation compared to those that account for the structure of the road network. Secondly, there is a substantial difference between the polygon method and the buffered line method.