Case Study:

Sacramento, California

Methodology

Modeling Approach

Standard travel demand models are capable of measuring the transportation impacts of alternative land development patterns. There are at least three reasons, however, to apply a transportation-land use model such as MEPLAN, TRANUS, or UrbanSim (Figure 2):

1. To measure the effect of alternative transportation investments and policies on land use patterns (1);

2. To consider the resulting feedback of these land use changes on transportation performance and related impacts (2); and

3. To measure the effect of alternative land use policies, such as zoning or tax incentives, on land use patterns and the resulting transportation impacts (3).

Figure 2. Relationships Modeled by Travel Demand and Land Use Models

In this study, two separate modeling approaches are used and the results are compared. The approaches are:

• Using a travel demand model only. Under this approach, alternative transportation investments and policies are simulated by changing network characteristics in the travel demand model. The effects of land use policies are simulated by changing the geographic distribution of future development. This approach is used widely by metropolitan areas throughout the United States.

• Using a travel demand-land use model. Under this approach, an integrated model is used that includes feedback between transportation accessibility and land development. It also allows land use policies, such as development fees or zoning changes, to be modeled directly by influencing the price and availability of land.

Under both approaches, changes in emissions are then calculated from transportation system changes using an emission factor model.

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