As alternatives have been developed, GIS has been introduced as a means of evaluation to assist in deciding which ones best meet the overall needs and concerns of the region. It is the purpose of this paper to describe the alternatives and illustrate how GIS is aiding planners in this complex decision making process. Two primary GIS applications will be described: the determination of wetland impacts and right-of-way acquisition costs. Each application will include a discussion of database creation using high resolution aerial photography, the overlay analysis, final reporting procedures, and benefits of using GIS versus previous methods of evaluation.
INTRODUCING THE I-4 MULTI-MODAL MASTER PLAN
The Interstate 4 (I-4) Multi-Modal Master Plan (MMMP) is being
developed by District 5 of the Florida Department of Transportation
(FDOT) as a response to the dynamic growth of East-Central Florida.
This region includes three rapidly growing metropolitan statistical areas:
Orlando, Daytona Beach, and Melbourne. The I-4 corridor directly links
two of these areas, Orlando and Daytona Beach. In order to address the
rapidly increasing travel demand of the region, this study is being
developed to serve as a guide for enhancing the I-4 travel capacity over
the next 25 years.
There are two stated goals for the I-4 MMMP. The first of these is that
the I-4 MMMP shall present strategies to increase mobility and decrease
travel time within the I-4 corridor in an effort to promote quality of life
and economic viability in Central Florida. The second is that the I-4
MMMP shall present strategies to promote protection of sensitive
environmental areas and neighborhoods within the study areas.(1)
The I-4 MMMP study has been organized into a three-tier alternative
evaluation process. Each tier is designed to narrow the range of
development alternatives. For the purpose of this study, development
alternatives have been identified as conceptual mobility enhancement
alternatives (CMEAs).
In Tier 1 of the study, 14 CMEAs were defined. These were designed as
broad corridor alternatives to provide a wide range of flexibility in
preparation for Tier 2.
Tier 2 narrowed the focus of the study to 9 CMEAs. These CMEAs
were developed with a number of guidelines. Among the guidelines
were the following: (2)
1. Lane additions are generally limited to the existing I-4 alignment
due to extensive development within the I-4 corridor. This will
minimize the high cost of right-of-way acquisition.
2. No more than 10 lanes are considered for I-4, responsive to
FDOT policy for its interstate highways.
3. Two transit technologies are being considered: extensive express
bus service operating from Park and Ride lots adjacent to I-4
and light rail transit service between Seminole and Osceola
Counties.
4. Intercity high speed rail (HSR) will pass through the region in all
alternatives. In some CMEAs, the HSR remains within the I-4
median, but in others, the HSR will leave and reenter the I-4
corridor.
5. Four alternative light rail transit alignments will be evaluated.
These alignments will utilize variations of being in the I-4
right-of-way or adjacent to the CSX rail line, with the objective
of maximizing existing transportation right-of-way or minimizing
the difficulty in obtaining new rights-of-way.
6. All CMEAs will provide for exclusive special use lanes for high
occupancy vehicles or single occupant vehicle through-trips.
An additional aspect of Tier 2 is that it was expanded to include recent
federal requirements for preparation of "major investment studies"
(MIS) evaluating the financial feasibility of all CMEAs and potential
sources of funding for recommended improvements.
Tier 3 of the I-4 MMMP was intended to focus on areas identified in
Tier 2 that required additional analysis and study due to the complexity
of design. It also included the development of a final recommended
CMEA.
DETERMINING THE ROLE OF GIS
The procedure for determining how GIS would become a tool in
providing information for the I-4 MMMP was to evaluate the structure
and components of the study. A dialog was initiated between
transportation planners and GIS specialists. Given that among the
stated goals of the I-4 MMMP was protection of environmentally
sensitive areas, it was determined that the most immediate way GIS
could benefit the study was in the performance of a wetland impact
analysis on the Tier 1 CMEAs. This would allow for a quick
determination of CMEAs that were non-viable due to potential for
significant adverse impact on wetlands. This would also save the
project many man-hours in that the previous method was to plot each
CMEA on top of aerial imagery, photointerpret the wetlands, and
calculate the impacts by hand with a planimeter. An added benefit from
using GIS to calculate the impacts would be the increased accuracy of
wetland impact acreages. Additionally, in the course of discussions, it
was determined that GIS would support the need to evaluate the impact
of CMEAs on surrounding neighborhoods and development. This
would be accomplished by performing a land use impact analysis. In
anticipation of the Tier 2 MIS enhancement, it was also determined that
if GIS could calculate the impact on each land use type, a procedure
could be developed to determine the actual estimated cost of acquiring
these as right-of-way. This right-of-way cost acquisition analysis,
although developed during the course of Tier 1, would be used on all
Tier 2 and Tier 3 CMEAs. This analysis would also save the I-4
MMMP time and money in the same manner as the wetland impact
analysis, by usurping manual calculation methods. A final aspect of
these analyses, determined in the discussions, is that the output
information they would provide would need to be reported according
to logical sections of the study area as well as by drainage basin in the
case of the wetland impact analysis.
DATABASE CREATION
After the determination of GIS applications, the need for the following
GIS databases was identified:
1) wetland polygons
2) land use polygons
3) segments of land use cost per acre variation
4) study area sections
5) drainage basins
6) Tier 1 CMEA corridors
7) Tier 2 CMEA right-of-way acquisition polygons
8) Tier 3 CMEA right-of-way acquisition polygons
Wetlands
The first database created was the wetland coverage. In discussions
with CMEA design engineers, it was determined that all wetlands within
1000 feet from the existing right-of-way centerline would be mapped.
The initial step in creating this coverage was plotting overlapping hard
copies of digital raster images for the entire study area corridor. These
images contained a pixel resolution of 8 ft. The hard copies were then
sent to an environmental sub-consultant for photointerpretation of each
wetland boundary. The sub-consultant subsequently created an
identification numbering system and vegetation characterization for each
wetland. After completion of photointerpretation, the wetland
boundaries were digitized into a computer aided drafting and design
(CADD) file. ID numbers were entered as text. The CADD file was
subsequently converted to ArcInfo with the text being used to build
an ID attribute. This ID attribute was subsequently used to relate to a
database file containing vegetation codes. These codes were used to
classify each wetland as requiring the full prevailing land use cost per
acre or a nominal acquisition cost, reflecting its limited commercial
value. This classification was created as a new wetland attribute.
Tier 1 CMEA Corridors
The second database built was the Tier 1 CMEAs. Fourteen corridors
were designed by transportation design engineers and established in a
CADD file. Each corridor was then converted into a separate
ArcInfo coverage for individual overlay with the wetlands coverage.
Land Use
The next database needed and built was the land use coverage. This
coverage was constructed in much the same manner as the wetlands
coverage. Hard copies of the raster images were produced. These hard
copies were then used by transportation planners for photointerpretation
and groundtruthing of land use polygons. The hard copies, now
containing land use boundaries, were then used as a guide by CADD
operators in performing "on screen digitizing". Using the digital raster
files as a backdrop, each land use boundary was drawn directly on
screen into a CADD file. Land use identification was added to the file
as text. For the purpose of the I-4 MMMP, land use within the corridor
was divided into the following 9 categories.
BC Business Commercial
BI Business Industrial
RS Single Family Residential
RM Multi-Family Residential
I Institutional
VA Vacant Agricultural
VC Vacant Commercial
VI Vacant Industrial
VR Vacant Residential
The CADD file was then converted through a DXF file to an
ArcInfo coverage.
Right-Of-Way Cost Segments
In preparation for the right-of-way cost acquisition analysis,
transportation planners researched the current market value for the
defined I-4 land use categories. They determined that the cost per acre
for each land use category varied significantly based on its proximity to
highly populated areas. To address this issue in the analysis, a segment
coverage was developed dividing the I-4 corridor into 19 different
segments, representing generally homogeneous land use characteristics
within each segment. Each of these segments contained a different cost
per acre for the land use categories. A series of items were defined in
the coverage to represent each cost per acre value. Additionally
segment number and description items were added to the polygon
attribute table (.PAT). Finally, all of the corresponding values, segment
numbers and descriptions were entered for each segment. A sample of
the land use costs for the downtown Orlando segments can be seen in
Table 1.
Table 1. I-4 Corridor Segment Right-of-Way Costs (downtown Orlando
segments only) (Cost in $ dollars per acre)
SEG 5 SEG 6 SEG 7 SEG 8
FLORIDA O.B.T. EAST/WEST LAKE
TURNPIKE TO EXWY. TO IVANHOE
TO EAST/WEST LAKE TO
LAND USE O.B.T. EXWY. IVANHOE PAR. AVE.
BC 3,800,000 3,800,000 4,900,000 3,800,000
BI 2,750,000 2,750,000 2,765,000 2,765,000
RS 650,000 650,000 575,000 650,000
RM 765,000 765,000 675,000 765,000
I 200,000 N/A 200,000 200,000
VC 750,000 N/A N/A N/A
VI 675,000 N/A N/A N/A
VR N/A 175,000 N/A N/A
(SGL FAM)
VR 200,000 200,000 N/A N/A
(MLT FAM)
VA N/A N/A N/A N/A
Tier 2 CMEA Acquisition Shapes
The Tier 2 CMEA coverages were built differently than Tier 1. These
coverages were not defined as 1 contiguous corridor polygon. Instead
each of these coverages were made up of multitudes of polygons
defining the difference between existing right-of-way and proposed
acquisition. Utilizing the I-4 CADD engineering design files, shapes or
polygons were drawn around each area of proposed acquisition, for
each CMEA, and isolated in their own layer. Each CMEA layer was
then converted to a separate ArcInfo coverage and each polygon
was tagged with an item identifying the CMEA. For a visual
representation of these acquisition shapes see Figure 1.
Study Area Sections
In order to evaluate I-4 MMMP land acquisition costs according to
defined study area sections, a coverage was created similar to the cost
per acre segments. A polygon coverage was generated dividing the I-4
corridor into logical sections. These sections were defined by significant
mile posts, interchanges, or significant change in condition. A
description of these can be seen in Table 2.
Table 2. I-4 Corridor Sections
CORRIDOR BEGIN END END MILEPOST
SECTION MILEPOST MILEPOST DESCRIPTION
S-1 MP 57.8 MP 61 South of Disney Road "B"
(Polk/Oceola Co. Line)
S-2 MP 61 MP 69 South of Lake Avenue
S-3 MP 69 MP 73 South of Sand Lake Road
S-4 MP 73 MP 80 South of O.B.T.
C-1 MP 80 MP 85 South of Princeton Street
C-2 MP 85 MP 91 South of S.R. 436
N-1 MP 91 MP 99 South of S.R. 46A
N-2 MP 99 MP 104 South of U.S. 17-92
V-1 MP 104 MP 107.5 South of Dirksen Drive
V-2 MP 107.5 MP 119 North of S.R. 44
V-3 MP 119 MP 132 South of I-95
Drainage Basins
In Tier 2 of the analysis, not only was it necessary to summarize wetland
impacts by each CMEA, but it was also necessary to summarize the
information by each surface water drainage basin. To accomplish this,
ArcInfo coverages representing drainage basins were acquired from
both the South Florida Water Management District, and the St. Johns
River Water Management District.
Tier 3 CMEA Acquisition Shapes
The final database built was a single coverage representing the Tier 3
CMEA right-of-way acquisition polygons. It was created in the exact
same manner as those representing Tier 2 CMEAs.
THE OVERLAY ANALYSES
Wetland Impacts
Tier 1 of the I-4 MMMP used GIS to perform a very basic wetland
impact analysis. Each of the 14 CMEAs were overlaid with the
wetlands coverage to create a lump sum impact acreage quantity for
each CMEA. In Tier 1, wetland vegetation types and other information
were not required. Tiers 2 and 3 required more detailed analysis. It
was in these phases that wetland ID numbers were related to a database
containing vegetation types. It was also in these phases that vegetation
types were used to identify each wetland as either a full or nominal value
wetland. Once this new information was added to the wetland
coverage, each CMEAs acquisition shapes were overlaid with the
wetlands. Subsequently, this product was overlaid with the study area
sections coverage to provide a summary breakdown of impacts for each
logical section. In addition to a CMEA-only impact analysis, the
wetland impacts for each CMEA had to be overlaid with surface water
drainage basins for impact summary per basin. A visual representation
of this analysis can be seen in Figure 2.
Right-Of-Way Acquisition Cost
The right-of-way acquisition cost analysis was completed during Tier 2
and Tier 3 of the study. The first step in this analysis was to create a
subset from the wetland coverage, of all wetlands designated as being
nominal value wetlands. By overlaying this coverage with the the base
land use coverage, these nominal value wetlands would be added as a
new land use type (WN). For other wetlands, the prevailing initial land
use type would serve as the cost indicator. The second step was to
overlay the base land use coverage with the right-of-way cost per acre
segments. This provided a land use coverage containing cost per acre
information. The third step in the process was to overlay the study area
section coverage to allow a breakdown of the final summary by logical
sections. The fourth and final overlay step was to overlay this land use/
cost per acre/section coverage with each CMEA to create land use
impacts. Once the impacts were determined, an acreage item was
created and used to multiply each land use polygon acreage by its
corresponding cost per acre. This information was stored in a total cost
item for each land use type. A visual representation of this analysis can
be seen in Figure 3.
SUMMARY AND REPORTING PROCEDURES
Wetland Impacts
For the wetland impact analysis, a summary was created of impacts
according to the following hierarchy: study area section, vegetation
type, and nominal or full value. A second summary for wetland impacts
included impacts by drainage basin for each section.
Right-Of-Way Costs
For the right-of-way cost summaries, a summary was created
summarizing land use impact acreage and total costs according to the
following hierarchy: study area section and land use type.
These summaries were converted from database file format to a
spreadsheet format for final reporting.
CONCLUSIONS
In evaluating the utilization of GIS in the Interstate 4 Multi-Modal
Master Plan, it has been concluded that GIS has enhanced the Plan's
ability to achieve its stated goals by providing a higher level of accuracy
in assessing sensitive environmental and neighborhood impacts, as well
as providing extremely valuable cost information in support of the
Major Investment Study. GIS has accomplished these objectives, while
at the same time significantly reducing the cost of the MMMP.
END NOTES
(1) I-4 Multi-Modal Master Plan, Tier 2/Major Investment Study;
Definition of Alternatives, Prepared for Florida Department of
Transportation, District 5 by the PBS&J Team, August 1995.
(2) I-4 Multi-Modal Master Plan, Tier 2/Major Investment Study;
Definition of Alternatives, Prepared for Florida Department of
Transportation, District 5 by the PBS&J Team, August 1995.