importance of high resolution map-based tools for cycling compared with motorised modes. Local transport budgets also increase demand for local cycling targets that open source tools such as the PCT could enable, as described in the Discussion. Planning new cycle paths requires many decisions to be made, including in relation to the width (Pikora et al., 2002; Wegman, 1979), quality (Heath et al., 2006), directness (CROW, 2007) and geographic location of the paths. Yet while much guidance has been produced regarding physical design (e.g. Transport for London, 2015; Welsh Government, 2014), little work has explicitly tackled the question of where high quality infrastructure should be built (Aultman-Hall et al., 1997; Larsen et al., 2013; Minikel, 2012). Within this policy context, the PCT focuses explicitly on the question of where to build rather than what to build, although it does provide evidence on potential capacity requirements across the route network. There is an emerging literature exploring cycling rates and potential rates of growth. Much of this work is practitioner-led, as detailed in an excellent overview of developments in the USA (Kuzmyak et al., 2014). With the notable exceptions of Larsen et al. (2013) and Zhang et al. (2014), the methods reviewed in this section are not simultaneously route-based , systematic , quantitative and scalable , some of the key features of the PCT. The work can be classified in a number of ways, including by the main mechanism of the tool (e.g. facility demand or mode choice models), the format of its outputs (e.g. spreadsheet results, GIS-based map or on-line, interactive map) or by the main level of the input data used. In these terms, the PCT is based on a mode choice model (representing the shift to cycling from other modes) operating primarily at the origin-destination level, which provides outputs in an online, interactive map. For research into cycling potential (and the resulting models) to be useful for local transport planners, their spatial scale must coincide with those over which the planning process has some control. For this reason we focus on scale as the primary way of categorising research 4 2.2 Research into cycling potential