Rachel Hough and Joey Gordon

Streamlining Transportation Planning by Performing Environmental Analyses with GIS

The Turnpike District of the Florida Department of Transportation is constantly identifying and evaluating potential projects in order to enhance the service that is provided to its riders. The current effort is termed the "Turnpike System Plan" (TSP) and will result in a financially feasible long-range transportation plan for the Turnpike District. The TSP evaluation is a multi-step process that begins with an initial evaluation of the environmental conditions surrounding the proposed project. This evaluation is made possible through the use of ArcView Version 3.0a and a variety of GIS data that has been acquired from various State and local governments.

 

Introduction

 In 1997 the Turnpike District launched a two-year planning study to identify and evaluate potential Turnpike projects throughout the State. This study, the Turnpike System Plan (TSP), will provide the Turnpike District with a financially feasible long-range transportation plan for all Turnpike facilities statewide. The study addresses improvements and expansions needed through the year 2020.

The Turnpike System Plan was developed into a three-phase study that began with project search activities. The Turnpike Administrators wanted to develop a plan that was based on the public's view of the transportation needs of the State in addition to the opinions voiced by the local governments. Their plan was an enhanced public involvement effort.

 

Phase One: Project Search

Phase One began with over 120 meetings held with FDOT Districts, Metropolitan Planning Organizations, and other transportation, business, neighborhood, and environmental groups. At the meetings, participants were asked to identify potential projects in their area that may be appropriate for Turnpike District's consideration and participation. Over 125 various projects were identified as candidates to be evaluated in the planning study.

Following Phase One, the projects were divided into eight project types:

 

Phase Two: Project Evaluation

Phase Two began in May 1998 and continued throughout the remainder of the year. The evaluations of the projects were based on four critical issues:

These issues were also called 'fatal flaws' because of their ability to stop a project's development. It was the fourth fatal flaw, the environmental evaluation, that relied heavily on GIS data and capabilities.

 

Methodology

Several steps were required to create a database that could provide for all environmental analyses. The first action was the collection of many datasets from a variety of State government offices. As a result, the data were in different projections which required the use of ArcInfo to reproject the data to match the current Turnpike District datasets. Once the basemap data layers were in place, new ArcView shapefiles of the potential projects were created. Several engineers, who provided the designs for the new and modified interchanges, created the drawings which were incorporated into the database.

Several key environmental issues were evaluated using a GIS:

The datasets were collected from a variety of sources with the majority coming from the Florida Department of Environmental Protection. Other sources include the Florida Department of State, Bureau of Archaeological Research, the Florida Water Management Districts, the Florida Game and Fresh Water Fish Commission, the U.S. Fish and Wildlife Service, the Federal Emergency Management Agency (FEMA), and the Florida Natural Areas Inventory (FNAI).

The analyses for the Environmental Impact Fatal Flaw Study used ARCINFO for all data processing and ArcView to determine the locations of possible environmentally sensitive sites. ArcView was also used extensively for producing maps. The proposed new interchanges and interchange modification projects were the first to go through the environmental evaluation phase. Most interchanges were no larger than 1 square mile which allowed for a simple analysis. Two extensions were used in conjunction with ArcView 3.0a; the sample buffer extension and the Xtools extension.

For the Turnpike System Plan analyses, a buffer of 2,000 feet was constructed around each interchange. The buffers were created for two reasons: 1) the buffer provided a clear boundary for the environmental fatal flaw analyses. If any fatal flaw was located inside the study area, it could be a significant threat to the feasibility of the project, 2) the graphics created by the buffers were used to clip or cut the data layers needed for the analyses.

The clipping of the data layers allowed for a quicker evaluation of large data layers and accurate calculation of percentages of polygon features within the study area. For example, the National Wetlands Inventory data is a large dataset and can be time consuming to evaluate. The problem encountered was that the Xtools extension did not use a graphic object to clip the data layers. Xtools requires the use of another shapefile, commonly called the clipping theme. In order to make a shapefile out of the graphic object on the View, the following steps are required:

This shapefile can be used once the edit mode is turned off. This is done by selecting the "stop editing" option under the Theme Menu. Once the new shapefile containing the buffer was created, the data was clipped by the buffer polygon. The Xtools Extension was used to produce a new shapefile containing the clipped data of interest. Clipping the data was one step using the Xtools extension.

This was the method used for the new interchanges and the interchange modification projects. However, the proposed Turnpike expansion projects were handled differently. This was because many of the expansion projects were new linear corridors and were at least 5 miles long. Therefore, a 2,000-foot buffer wouldn't show all of the environmental issues possibly posing an impact on the project. For those projects, a study area boundary was created by viewing all of the environmental data layers in a View window and then drawing a boundary that would include all of the possible impacts that needed to be reviewed. This graphic object on the View window was then cut and pasted into a new shapefile to create a clipping theme. Following all data processing, an ArcView project file was given to professionals for review.

After each project was reviewed for the existence of an environmental issue or impact, it was graded according to the quality and quantity of the encroachment. The projects were ranked by data layer (wetlands, contamination, endangered or threatened species, etc...) and given a rating of High, Medium, or Low. If a project was scored with one or more environmental categories ranked as "high", it was dropped from consideration and did not undergo any further evaluation. The "high" rating meant that the issue would be costly to mitigate or generate significant environmental opposition. An environmental impact summary was also written describing the fatal flaw, examining the laws surrounding the issue, and the recommended actions. All of the proposed System Plan projects were evaluated using these methods.

Following all analyses, a two-page summary report was generated for each project which included a map showing the recommended interchange design or expansion project alignment. A meeting was held in the first week of October 1998 with Turnpike Management to discuss and screen each potential Turnpike System Plan interchange, access, and widening project. During the October meeting, approximately 8 projects, three new interchange projects and 5 access road projects, were dropped from consideration for the Plan. In January 1999, a meeting was held to review each expansion and widening project. A general project concept report was developed for those proposed projects that had advanced through the Phase Two screening processes. Depending on the project's complexity, the Phase Three evaluation may also require refined traffic estimates and more detailed financial and environmental analyses to assist in final project selection.

 

Phase Three: Project Selection and Plan Preparation

The Turnpike District is currently in the final stages of Phase Three. A final review has been made where approximately 35 projects were selected for inclusion in the Turnpike System Plan. Public meetings with local governments, MPO's, community groups and citizens will follow. At the meetings, Turnpike Administrators will discuss the Plan's recommendations and each area's specific projects.

 

Conclusion

The Turnpike System Plan will develop a long-range transportation plan for Florida's Turnpike District. This study relied heavily on the use of a GIS to perform the environmental analyses and project selection. This Plan will provide the planning and financial framework for Turnpike System improvements and expansion well into the next century.

Rachel Hough
GIS Analyst
URS Greiner Woodward Clyde Inc.

Joey Gordon
Systems Analysis Manager
Florida's Turnpike