REGIONAL SETTING OF THE THREE COUNTY STUDY AREA 
FIGURE 5. 
  
  
  
      
    
    
   
  
    
   
  
  
  
    
alternative. The scope of the project was therefore quite broad; it 
extended considerably beyond the capabilities of computer aided assess- 
ment embodied in GMAPS-GCARS. Nevertheless, the GMAPS-GCARS systems 
played a significant role in the analysis of location alternatives and 
in the assessment of each. 
To develop as comprehensive and complete a group of highway alternatives 
as possible the GMAPS-GCARS analyses were checked by an independently 
conducted conventional transportation analysis. The combination of 
these two procedures provided as objective a group of alternate corridors 
as possible. 
It was important that potential highway corridors selected for detailed 
cost evaluation and environmental impact assessment be identified on the 
basis of social, economic and ecological considerations as well as en- 
gineering feasibility. A rectangular detailed study area was selected 
for the GMAPS-GCARS analyses(Figure 5). This area was chosen for a 
number of reasons. Important considerations were that it encompassed 
all previously expressed corridor preferences; it incorporated I-90 
and existing Southern Tier Expressway segments; it enabled all reasonable 
alternative corridors to be considered by embracing an area sufficien- 
tly broad to allow for any practical corridor circuity; it was the area 
which earlier study had shown to be of greatest impact, influence and 
interest with reference to the Southern Tier Expressway. 
Corridor alternatives were evaluated by two methods: a computer-aided 
method involving the GMAPS-GCARS programs, and an independently con- 
ducted conventional transportation analysis. Data for 22 baseline maps 
(Table 1) describing a variety of engineering, cultural, economic, and 
environmental factors were plotted on 1:62500 scale base. These data 
were converted to a cellular matrix representation and entered into com- 
puter storage via the GMAPS programs. The resolution of this digital 
data was 3.16 hectares, or a rectangle (cell) 198 meters by 158 meters. 
A total of almost 180,000 cells were required. 
The GMAPS programs allow for the manipulation of data-bases to create 
new models by overlaying, or "compositing", techniques.  GMAPS also 
allows for the display of all maps (Figure 6). As shown in Table 1, 
the GMAPS process produced a series derivative, determinant, and ultim- 
ately composite models which showed the desirability of highway corridor 
location based on : (1) engineering feasibility; (2) improving social 
and economic conditions; and (3) environmental impact. These three 
composite models were calibrated and approved, then combined in various 
ratios to produce a sequence of total highway corridor feasibility 
models. 
GCARS procedures were applied to these models (Figure 7). After many 
such analyses were run, a general pattern emerged, with five major al- 
ternatives dominating. These results were synthesized with those ob- 
tained by conventional techniques, and 12 detailed alternative corridor 
locations were selected, using various combinations of 31] sections. 
These corridor locations were re-entered into the GMAPS-GCARS programs. 
Computation of the levels of impact of each alternative of any baseline