Current Systematic Evaluation Methods
This section is concerned with models that evaluate TDM cost effectiveness for public funding purposes. They provide formal ways to model the impacts of TDM alternatives in a predictive fashion. The ensuing literature review focuses on methods incorporating (1) costs and benefits in economic terms accompanied by (2) a calculator or estimator or “model” for projecting TDM effects of one or more TDM strategies being considered for implementation.
The literature search uncovered few existing approaches to the evaluation of TDM impacts on a predictive basis. To date, most of the evaluation deals with the assessment
of individual pilot projects and vanpooling or user subsidies)
programs that focus on single TDM
(such as of these
methods take the form of calculators for the based programs. Usually, such tools are not based on simple rule-of-thumb approaches.
set up and predictive
benefits assessment of in nature, or if so, they
employer- tend to be
The review showed that the most common evaluation method is cost benefit analysis, as
it provides both a means of recommending and ranking constraints associated with these approaches are related to
each of the identified benefits evaluation of concurrent TDM
and costs, and the difficulty to provide strategies (i.e., synergistic effects).
These approaches are characterized by a structured approach to the quantification of benefits, such as travel time savings, congestion reduction, health and fitness. The methods provide ways to estimate the change in benefits brought about by different TDM strategies, as well as monetary values. The latter are usually provided in ranges and are the byproduct of current and past studies at an aggregate level.
COMMUTER Model V2.0
The COMMUTER model, developed by the Environmental Protection Agency, is intended to be used to project emission impacts of different TDM strategies of commuter choice incentive programs. The model is capable of estimating, at a sketch planning level, impacts of TDM strategies directed at affecting accessibility, transit time, walking time, parking pricing, modal and other subsidies[7, 8].
The impacts of alternative TDM strategies are estimated differently according to the
program being considered, as shown in Figure 1. programs,” such as alternative work schedules and projected by means of look-up tables. These look-up
For example, impacts of “soft employer support programs are tables provide modal incremental
changes that are associated application assumptions and total mode share sums to 100
with the programs levels of intensity. percent.
being considered, reflecting different A normalization procedure assures that