Urban Form and Greenhouse Gas Emissions

The paper assesses the effects of land use forecast scenarios on the urban form and GHG emissions from cars and light trucks using the Hoover Concentration Index and the transportation demand model. The paper uses 2007 land use forecast scenarios for the SCAG region. The Hoover Concentration Index for those different land use forecast scenarios indicate that the macro geographical scale population and employment generally become more de-concentrated in the Southern California region, while the smaller geographical scale population and employment distribution pattern is more diverse depending on the land use forecast scenarios. The Envision Scenario shows the different pattern from the spatially de-concentrated distribution of population and employment observed in the Trend Scenario or the Locally Preferred Scenario. The transportation demand model finds that the Envision Scenario shows the best transportation performances and reduces the most GHG emissions among five growth distribution scenarios. Although Envision Scenario can be proposed as an ideal future urban form, it might be unrealistic and locally unacceptable because of its aggressive allocation of additional population and employment into the limited opportunity areas of the Southern California region. This paper asserts that the identification of the optimal and locally acceptable urban form would warrant the successful implementation of Sustainable Communities Strategy (SCS) in the Regional Transportation Plan, as required in the Senate Bill (SB) 375 of California. This paper also suggests that an extended Compass Blueprint program would be an effective implementation strategy toward the more optimal urban form consistent with Envision Scenario to meet the ambitious emission target, and would warrant the success of implementing regional sustainable planning.