Quantifying the Net Social Benefits of Vehicle Trip Reductions: Guidance for Customizing the TRIMMS© Model

Document Type


Publication Date


Subject Area

infrastructure - vehicle, planning - travel demand management, ridership - forecasting, ridership - forecasting, ridership - demand, economics - benefits, organisation - management


Air quality management, Cost effectiveness, Forecasting, Social benefits, Travel demand management


This study details the development of a series of enhancements to the Trip Reduction Impacts of Mobility Management Strategies (TRIMMS©) model. TRIMMS© allows quantifying the net social benefits of a wide range of transportation demand management (TDM) initiatives in terms of emission reductions, accident reductions, congestion reductions, excess fuel consumption and adverse global climate change impacts. The model includes a sensitivity analysis module that provides program cost-effectiveness assessment. This feature allows conducting TDM evaluation to meet the Federal Highway Administration Congestion and Air Quality (CMAQ) Improvement Program requirements for program effectiveness assessment and benchmarking. This document provides guidance to help TDM professionals to use the model by selecting the appropriate cost parameters, providing referenced sources where to obtain such parameters, and by offering general guidance on how to incorporate data already at their disposal.