Estimating Vehicle Emissions in Response to Urban Sprawl

October 29, 2008 By: Tim Dolney

Simulation Process

Microsoft Visual Basic (VB) programming language was used to integrate all computational components and user interfaces of the model. The VB programming language was applied to GIS capabilities through a collection of embeddable mapping and GIS components. Additionally, a program with street-networking capabilities was used to simulate travel during the home-work journey.

With emission factors expressed as grams emitted per distance traveled, VERTUS calculates emissions based on distance traveled from new housing developments to HAPs and then to employment centers. These distances are determined through the algorithms implemented in the travel-simulation program, including a modified Dijkstra algorithm with a D-Heap. Road networks were constructed from U.S. Census TIGER (Topologically Integrated Geographic Encoding and Referencing system) Line Files. Internet map services were used to test distances reported by VERTUS to ensure consistency in results.

Complete Simulation Tool

Given that urban sprawl is a long-term and irreversible process, simulation is the best way to study how it will proceed and how it may impact the environment. VERTUS, coupled with UGS, offers planners, public officials, and environmentalists, among others, a complete planning tool capable of quantifying all environmental effects associated with urban sprawl. VERTUS is flexible: it provides a pre-defined value for each variable, but allows the user to override these values.

Simulation models vary from fully automated process to fully manual. When a simulation model is more automated, less user intervention is required, but at the same time, less customization is allowed. Alternatively, a higher degree of user intervention can be realized by allowing users to provide more information as input. Because VERTUS allows user intervention, multiple scenarios can be tested to see how each affects the amount of emissions generated. With the successful application to Geauga County, Ohio, VERTUS can be applied to other geographic areas for the same purposes. Those areas considering VERTUS need only obtain a copy of CTPP for their geographic region to estimate commuting parameters.

Manufacturers

The VB programming language was applied to GIS capabilities through ESRI's MapObjects. ESRI's NetEngine was used to simulate travel during the home-work journey. Internet map services from MapQuest, Google Maps, and Yahoo Maps were used to test distances reported by VERTUS to ensure consistency in results.