5. Alternative Options Sifting
The A9 route was split into 6 online corridor sections and GIS was used to plot 7 indicative alternative broad corridors (labelled A-G in Fig.2) which were considered as potential alternatives to dualling the current route. 20 near offline options around the existing A9 were also identified as alternatives to short sections of the online corridor.
The GIS databank was then used to extract information on the features and constraints within each online section, indicative alternative, and near offline corridor option footprint.
These analyses informed an Options Sifting Workshop, which resulted in a shortlist for further consideration, including the 6 online sections and 4 near-offline options (see Fig. 3).
A full description of the alternative broad corridors, the online and near offline options and a record of the constraints assessment, with reasons for elimination of options, is provided in the Options Sifting Report, attached as Appendix E to the Environmental Report.
Figure 2 Example GIS Overlay Analyses
Figure 3 Corridor options sifting process