Roadside Interview Data (RSIs) are the key data sources for providing travel patterns by journey purpose as they allow us to understand where people are travelling from and to and why they are doing so. These patterns also provide additional information about the relative attractiveness of nearby zones, which can then be used to adjust other local trips which do not pass through any of the RSI sites.

RSIs involve interviewing a sample of motorists on a given road and asking them about their origin postcode, destination postcode and the purpose of their journey. Such surveys are generally conducted on ‘average’ weekdays in ‘neutral’ months (ie between Tuesday and Thursday and in months such as May, March and September to November, although this can vary). Drivers are either be interviewed at the RSI site or given a freepost postcard survey form to complete and return.

The collected data are then checked and ‘cleaned’ to remove any ‘unlikely’ travel patterns and a factoring process is used to scale up the results to match the corresponding full traffic count at the RSI site.

RSIs are used both to build the model trip matrices and for calibration and validation of the model.

To view the location of RSIs used in TMfS:07, please visit the maps page.