resource costs. For example, in the case of parking resource costs, the model assumes that individual perceives 75 percent of the resource costs, with a required cost correction of 25 percent. A given TDM strategy might influence the way a user perceives this cost by either increasing or lowering the perceived component. By letting the researcher establish what should be included in perceived costs, and by assuming what individuals are able to internalize in terms of costs, the approach is likely to overestimate TDM benefits. 5
Second, the model does not rely modal shares tailored for New
on a pivot Zealand.
point formula, These shares
on a set of pre-estimated obtained from regional
transport demand models and used out a pivot logit or any equation. reliability of the modal share shifts
as fixed parameters in the spreadsheet, without calling As in the case of the EPA COMMUTER model, the relies upon regional estimates coming from traditional
four-step models. employed in these
As a result, the default parameters depend on models, which cannot be easily generalized in
the calibration processes a broader context.
5 For example, the model assumes a full resource cost of parking of $10.00 for the Auckland area for peak period commuting trips to the Central Business District (CBD). Then, it assumes that individuals only perceive 75 percent of such cost for a total of $7.50. On the other hand, the average parking fee is only $2.50 (page 29). Another example is provided by how walking and cycling accident costs. When computing the total health benefits of walking and cycling, the model assumes that these are resource costs that do not need to be discounted by the risk of incurring in accidents (e.g., individuals do not internalize the added risk of switching to walking or cycling).