Routes generated by CycleStreets.net do not necessarily represent the paths that cyclists currently take; route choice models based on GPS data have been developed for this purpose (Broach et al., 2012; Ehrgott et al., 2012). Of the available routes (see cy- clestreets.net/journey/help for more information), the ‘fastest’ option was used. This decision was informed by recommendations from CROW (2007), building on evidence of cyclists’ preference direct routes. The spatial distribution of cycling potential can be explored interactively by selecting the ‘top n’ routes with the highest estimated cycling demand (see the slider entitled “N. Lines (most cycled)” in Figures 3 and 4). Information about the aggregate cycling potential on the road network is shown in the Route Network layer. Because the layer is the result of aggregating overlapping ‘fast’ routes, and summing the level of cycling for each scenario (see Figure 5), it relates to the capacity that infrastructure may need to handle. Cycling along Otley Road (highlighted in Figure 5), under the Go Dutch scenario, rises from 73 to 296 commuters along a single route, but from 546 to 1780 in the Route Network. Note that more confidence can be placed in the relative rather than the absolute size of these numbers: the Route Network layer excludes within-zone commuters, commuters with no fixed workplace, and commuters working in a different region (see Figure 1). Route Network values also omit routes due to the adjustable selection criteria: maximum distance and minimum total numbers of all-mode commuters per OD pair. At the time of writing these were set to 20 km Euclidean distance and 10 commuters respectively. Nationally, the Route Network layer under these settings accounts for around two thirds of cycle commuters. ## [1] FALSE ## [1] FALSE 21