The GCARS Programs 
An entirely new sequence of GCARS programs was developed to interface 
with the GMAPS data base. These programs incorporated all the suggested 
improvements outlined earlier. A new minimum path technique had been 
proposed by the Ohio DOT. Further research and reprogramming of their 
algorithms resulted in marked reductions in computation times and core 
requirements. The new algorithm was substituted and comparisons in- 
dictated that it was 10-20 times more efficient. The new algorithm had 
several advantages; it allowed movement along diagonal directions; core 
requirements were drastically reduced; and computational efficiency was 
a linear function the length of the corridor. 
The GCARS programs produce maps of the routes, either on their own or 
superimposed on appropriate gray-tone cellular maps. They also produce 
statistical summaries which give the user the basic path totals, lengths 
and comparisons needed to make his assessments. Additionally, the 
planner is assisted in evaluating goal achievement and cost criteria. 
Achievement can be measured by comparing each alternative corridor gen- 
erated for some composite suite of goals to the optimal corridors pro- 
duced by evaluating each goal dependently. Cost evaluations are made by 
overlaying the generated choices on a construction cost model. 
GCARS Applications 
In order to demonstrate how these systems have evolved in the past decade, 
examples of an early GCARS I project are compared to a recently completed 
GMAPS-GCARS project. 
GCARS I Lafayette Indiana Study 
The study area was 19 by 24 kilometers and centered on the Lafayette- 
West Lafayette metropolitan area in an otherwise typically rural mid- 
western setting. The Wabash River valley formed the major topographic 
feature. A total of seven models were constructed. All utilized a 
comparatively large cell size of about 1 km. by 1 km. Over twenty 
combinations of factors and factor weightings were studied (13). Four 
selected corridor analyses are shown in Figure 4. While these do show 
how the optimal corridors shift to reflect different factor weightings, 
they also show the limitations of these early GCARS I programs. The 
movement along diagonals were not possible, resulting in inflated path 
totals, and the routes were only approximately located. Since the 1 km. 
resolution was too coarse to allow more precise definitions. 
The Southern Tier Expressway Study 
In 1975-76 the GMAPS-GCARS systems were utilized to aid in the environ- 
mental impact analysis of about 160 kilometers of new four lane highway, 
the Southern Tier Expressway in extreme western New York and Pennsylvania 
(Figure 5). The impact assessment included a description of the trans- 
portation and transportation-related problems, resulting transpor - 
tation needs,specific project objectives, transportation location 
alternatives, and an evaluation of potential impact associated with each