The report summarized the approaches used to date, conceptualized a new approach and introduced a model that allows some regions to use local data or opt to use defaults from national research findings, select the benefits and costs of interest, and calculate the costs and benefits of the program. The model, TRIMMS, resulting from this project provides a comparative assessment of TDM for program managers and funding agencies like FDOT to make informed decisions on where to spend finite transportation dollars based on a full range of benefits and costs. The approach is consistent with other benefit/cost analyses. Its accuracy and the perceived fairness are critical when significant funds are at stake.
A key strength of this model is its wide range of benefits and costs that
agencies throughout the country.
This model focuses on the societal costs and benefits at a regional or worksite level. Future research could seek to enhance the model to include more of the internal benefits to employers (e.g., changes in worker productivity, reduction in overhead, changes in employee retention, etc.). Certainly, the challenge of this future enhancement is finding data relating to given TDM strategies to such business outcomes, given businesses seeking to maintain a competitive advantage. Another area of future research would be to develop regional or local values for some of the externalities and elasticities.
Finally, a byproduct of this research effort that goes beyond the initial research objectives is the development of a structured approach to evaluate the impact of soft programs. Compared to the currently available soft program evaluations methods, the approach developed in this report provides a less heuristic method of estimation resulting in statistically robust mode share impact predictions. Another future area of analysis would be the refinement of such a model to provide a standardized approach to soft program impact assessment.