Travel, Emissions, and Welfare Effects of Travel Demand Management Measures

Land-use intensification measures and pricing policies are compared and combined with high-occupancy vehicle (HOV) lane and light-rail transit expansion scenarios in the Sacramento, California, region and evaluated against travel, emissions, consumer welfare, and equity crite- ria. A state-of-the-practice regional travel demand model is used to sim- ulate the travel effects of these scenarios. The Small and Rosen method of obtaining consumer welfare is applied to the mode-choice models in the travel model. The most politically feasible scenarios were found to provide at best only modest improvements in congestion and emissions. Welfare losses were obtained for the HOV lane scenario, suggesting that care must be taken in project planning to ensure that savings in travel time are large enough to offset the unobserved cost of increased travel by car. Transit investment and supportive land-use intensification pro- vided larger reductions in congestion and emissions and increased con- sumer welfare for all income classes. As a group, the scenarios that included pricing policies provided the greatest reduction in travel delay and emissions, increased total consumer welfare, and imposed losses on the lowest income group. However, it may be possible to combine pric- ing policies with more significantly expanded transit and roadway capacity and compensatory payments to increase consumer welfare for all income classes. Many general overviews of transportation demand predict world- wide increases in vehicle kilometers traveled (VKT) and mobile emissions resulting from higher incomes, the shift to more energy- intensive modes (1), and vehicle growth rates that exceed popula- tion growth, particularly in developing countries ( 2). In the United States, lower out-of-pocket travel costs, decentralized basic em- ployment (3), and shelter costs that have increased in proportion to income (and thus households trade longer commutes for cheaper housing) have increased VKT, energy use, and mobile emissions. All these trends have caused concern, and attention has focused on travel demand management measures (TDMs). The federal Clean Air Act requires annual reductions in nonattainment pollutants. The California Clear Air Act requires reductions in the growth rate of VKT, increases in average vehicle occupancy during commute periods, and no net increase in mobile emissions after 1997. Both acts require the adoption of all feasible transportation control measures. In this study, land-use intensification measures and pricing poli- cies are compared and combined with high-occupancy vehicle (HOV) lane and light-rail transit expansion scenarios in the Sacra- mento region of California. A state-of-the-practice regional travel demand model (SACMET 94) is used to simulate the travel effects of different scenarios, and California emissions models (DTIM2 and EMFAC7F) are used in the emissions analysis. The Small and Rosen method (4) of obtaining consumer welfare from discrete- choice models is applied to the mode-choice models in the travel model. The scenarios are evaluated against travel, emissions, total consumer welfare, and equity criteria.