localised pro-cycling interventions should be prioritised. By showing potential health-related benefits the tool provides various metrics for transport planners, going beyond the number of additional trips. Illustrative uses of the PCT demonstrated the potential utility of the tool, for example by showing settings in which the spatial distribution of cycling demand is likely to shift as cycling grows. 

In addition to creating an evidence base for planning specific routes and area-based interven- tions, the long-term Go Dutch and Ebikes scenarios could be used for envisioning different transport futures (Hickman et al., 2011). The PCT could also: help translate national targets into local aspirations (as illustrated by the Government Target scenario); inform local targets (e.g. by indicating what the potential in one region is relative to neighbouring regions); support business cases (by showing that there is high cycling potential along proposed routes); and help plan for cycle capacity along the route network via the network analysis layer. Ongoing case study work with stakeholders will be needed to establish and develop these uses. Future developments will be facilitated by the open source code-base underlying the PCT (see github.com/npct) (Lima et al., 2014). 

As with any modelling tool, the approach presented in this paper has limitations: the reliance on Census origin-destination (OD) data from 2011 means that the results are limited to commuting and may not encapsulate recent shifts in travel behaviour, and the user interface is constrained to a few, discrete, scenarios. These limitations suggest directions for future work, most notably the use of new sources of OD data. 

There is often a tension between transparency and complexity in the design of tools for transport planning. Excessive complexity can result in tools that are ‘black boxes’ (Saujot et al., 2016). In a context of limited time, expertise, and resources, Saujot et al. caution against investing in ever more complex models. Instead, they suggest models should be more user focussed. The PCT’s open source, freely available nature will, we believe, facilitate the future development of the PCT organically to meet the needs of its various users. To 

