Case Study:

Orange County, California

Application

Uses of GIS

Since its inception at OCTA, the GIS unit has evolved into a valuable technical resource that is utilized for many interdepartmental tasks. Some uses of GIS at OCTA for regional transit service planning include:

• The analysis and visualization of the accessibility of bus stops by associating bus stops with socioeconomic data in a GIS environment;

• The evaluation of transit service changes by using GIS to analyze alternative alignments of transit routes. The analysis determines how service changes can affect ridership;

• Displaying and validating travel demand model inputs and results by linking model data with GIS layers. (OCTA maintains an in-house demand forecasting model.) Modelers can enter, display, and store input parameters for travel demand models in a GIS environment. They can also link model output data to transportation network layers in a GIS to display results such as projected traffic volumes; and

• Developing regional measures of accessibility of population to transit.

GIS also assists with many other aspects of transit service planning, including maintaining an inventory of bus stops; visualizing passenger count data; administering and analyzing on-board surveys by linking survey data with transit route data; displaying survey data; linking passenger count data to transit route data to analyze the productivity of specific lines; and analyzing the travel characteristics of paratransit patrons to determine their potential for fixed-route bus service.

• In addition to transit-specific uses, GIS has been used to support other business functions at the agency, including:

• Enhancing public outreach by producing high-quality maps that display transit facilities and demographic information;

• Supporting the marketing of transit services by analyzing service improvements and presenting the results to stakeholders; and

• Managing highway performance data by storing and maintaining traffic volumes, capacity, and level of service.

Two examples of OCTA's use of GIS for transit planning are presented below. The first describes how the spatial distribution of socioeconomic data is revealed in more detail by employing spatial overlay techniques. The second example illustrates the analysis of transit accessibility using GIS. Potential extensions to regional transit and transportation planning are also discussed.

The examples presented below are only a few of the many applications of GIS-based analysis for transit planning. An additional application, in which OCTA used GIS to map transit survey data, is described in Transportation Case Studies in GIS (FHWA, 2000).

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