Transportation Demand Management (TDM)

Transportation Demand Management (TDM) is the use of strategies to inform and encourage travelers to maximize the efficiency of our transportation systems leading to improved mobility, reduced congestion, limit single occupancy vehicle (SOV) trips, and lower vehicle emissions. TDM strategies have been shown to be a cost-effective means of meeting key policy objectives.  

TDM is particularly relevant to the state of Tennessee, according to the 2022 US Census, Tennessee has a higher percentage of work-related travel involving a SOV trip (75.0%) than the national average (68.7%) [1]. This high rate of SOV travel has significant impacts on Tennessee’s traffic congestion and travel time reliability, as well as the health of our communities. High levels of SOV travel exacerbate congestion, leading to longer travel times and reduced mobility for commuters. Additionally, SOV travel contributes to poor air quality, which can have an impact on the health of vulnerable populations. 

By strategically deploying TDM strategies, Tennessee can potentially reduce SOV trips and the vehicle miles traveled (VMT) on Tennessee roads. By reducing VMTs, Tennessee could extend the life of its roadway systems, spend less on road maintenance, reduce congestion, and allocate tax-payer dollars to other areas of interest and more importance. 

If you’re interested in estimating the benefits of a particular TD program, LDA Consulting’s TDM Return on Investment Calculator is a valuable tool to consider. This calculator helps users calculate vehicle trips and miles reduced by their TDM programs, and to calculate benefit-cost ratios or ROI. You can download the spreadsheet-analysis method and user manual by visiting Mobility Lab | TDM ROI. 

Additionally, the Center for Urban Transportation Research has developed the TRIMMS model 4.0 (Trip Reduction Impacts of Mobility Management Strategies), which has incorporated new background data on TDM strategies. TRIMMS assesses the impact of a broad range of TDM initiatives and provides cost-effectiveness analysis of programs such as net program benefits and benefit-to-cost ratio analysis at an area-wide or site-specific level. The model is based on default literature-based parameters for 99 metropolitan areas and constant-elasticity demand functions. You can download TRIMMS by visiting Mobility Lab | TRIMMS 4.0. 

[1]  U.S. Census Bureau. "Commuting Characteristics by Sex." American Community Survey, ACS 1-Year Estimates Subject Tables, Table S0801, 2022