The question of regional trip rate variation and the inclusion/exclusion of TRICS sites by region has been raised numerous times by TRICS users over the years. The position of TRICS has always been that users should exercise good practice by considering local factors when using the site selection filtering process in our system instead of automatically rejecting some otherwise useful sites merely based on the region(s) that they are situated within. To finally address this issue on a technical and evidence-based level, in 2019 a technical analysis took place using the large database at our disposal, to examine and understand vehicular trip rate generation by region when compared to trip rate generation by TRICS location type. The results of this research provided hard evidence that clearly showed that significant correlations and patterns of variation only occurred when there were comparisons between location types, with comparisons between regions showing much more random and inconsistent results. This meant that we could build this clear evidence-based research into subsequent updates of our TRICS Good Practice Guide.
In short, there is no clear evidence within the thousands of surveys that TRICS has undertaken to show any logical reasoning for the automatic exclusion of sites based on region, whilst there is most definitely evidence to suggest that a more accurate approach is to assess the local factors that lead to true trip rate variation, such as TRICS location type, population levels, and public transport levels and accessibility, amongst other local influences. For example, a site in the North-East of England may have similar local characteristics to a site in the Midlands, Scotland or the South-West of England, or a site at the far edge of London may be considered like a site at the far edge of Manchester, Birmingham, or Glasgow. Similarities can be relative, for example in terms of the size of a town/city and the physical location of sites within them, but they can certainly exist across regions, just as the clear evidence gathered from our research showed. Comparing sites by region showed much more of a random and inconsistent scattering of trip generation levels, with the only conclusion being that any sort of consistent regional variation simply does not exist in the way that some practitioners may imply.
Therefore, TRICS Consortium Limited continues to urge practitioners to use our evidence-based research when it comes to selecting sites for the calculation of trip generation rates and avoid the unnecessary exclusion of sites based on region (which itself can reduce sample sizes to below robust levels). It is a much more accurate and correct practice to be inclusive by region and to focus more on the local variables where we have clearly found hard evidence that trip rate variation exists.
The full 2019 research report is called “A Comparison of Vehicular Trip Rate Variation by TRICS Regions and Location Types”, is freely downloadable, and can be found via the Technical Notes & Guidance Library on the TRICS website at the following location:
Technical Notes and Guidance
The 2024 TRICS Good Practice Guide is also present and freely downloadable at the same location and can also be easily accessed when using TRICS. For reference, section 4 of our guidance, called “Site selection by Region, Location Type and other data fields”, is a very good and handy reference in explaining how TRICS sites should be selected and covers the trip rate variation research discussed here. As always, the TRICS team are on hand to assist should any members of the TRICS Community have any questions of clarification.