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International Archives of the Photogrammetry, Remote Sensing 
earthwork costs using linear programming (LP), and estimates 
sediment production. The economic distribution of cut and fill 
quantities is determined by implementing the LP method of 
Mayer and Stark (1981). This method represents the earthwork 
allocation better than the other methods due to considering 
possible borrow and landfill locations and various soil 
characteristics along the roadway. Besides, it provides the 
optimal solution to the earthwork allocation problem. A linear 
programming code, using the idea of simplex algorithm 
(Bowman and Fetter, 1967), is developed to incorporate this 
method into the model. 
The average annual volume of sediment delivered to a stream 
from the road segments is estimated by using the method of the 
Geographic Information Systems (GIS) based erosion delivery 
model, SEDMODL (Boise Cascade Corporation, 1999). Some 
of the road erosion factors considered in this model include 
geologic erosion rate, road surface type, traffic density, road 
width and length, average road slope, average precipitation 
factor, distance between road and stream, cut slope cover 
density, and cut slope height. SEDMODL reasonably predicts 
the sediment delivery and defines the road segments with high 
sediment production. 
To develop additional road alignment alternatives, various 
feasible road paths can be traced out by the designer. For each 
alternative, the model follows the same procedure to find the 
optimal vertical alignment with minimum total cost. Therefore, 
the designer can quickly generate many alignments and select 
the optimal one among the alternatives in an efficient way. 
3. RESULTS AND DISCUSSION 
The model was applied to a study area of 55 hectares, located in 
the Capitol State Forest, Washington, the USA. The high- 
resolution DEM (Imx1m) of the study area was obtained from 
LIDAR (Aerotec, 1999). The attribute data including soil, 
hydrology, and geology data were provided by Washington 
Department of Natural Resources. Road design specifications 
(Table 1) and cost data in US dollars (Table 2) were obtained 
from the local sources in Pacific North West (PNW) (Kramer, 
200; USDA Forest Service. 1999). 
Initial road path was generated by establishing six intersection 
points on the 3D image of the terrain based on DEM data from 
LIDAR, while considering road design specifications and 
environmental requirements (Figure 2). The unit cost of this 
initial path was $36.88/m. Then, using optimization techniques, 
Table 1. The road specifications used in the example 
  
  
and Spatial Information Sciences, Vol XXXV, Part B7. Istanbul 2004 
Table 2. Local unit cost data for road construction in PNW 
  
  
Cost Items Costs 
Construction staking $ 778/km 
Clearing and grubbing $3700/ha 
Earthwork 
Excavation $1.6/m° 
Haul $1.3/m^-km 
Embankment $0.6/m° 
Disposal $0.1/m* 
Borrow material 
Excavation $1.8/m° 
Haul $1.3/m’-km 
Embankment $0.6/m° 
Surfacing 
Base course $3.9/m° 
Traction surface $11.8/m° 
Drainage and riprap 
Culvert $25 meter 
Riprap $10/m° 
Watering $3/kilo liter 
Seeding and mulching 
Material $0.5/kg 
Application $550 /ha 
  
the model located the optimal vertical alignment with the 
minimum unit cost of $27.74/m (Figure 3). Therefore, total road 
cost was reduced about 25% by the optimization model. Total 
amount of sediment delivered to streams from the road section 
was estimated as 0.84 ton/km. 
The results indicated that total construction cost was the largest 
cost component, followed by maintenance and transportation 
costs (Table 3). Within the construction cost components, 
surfacing cost was the largest, followed by earthwork allocation 
cost. Total cost of maintaining culverts and ditches and cleari ne 
bushes was the largest cost component in the maintenance costs. 
During the search process, the model calculated 147 feasible 
solutions out of 1200 automatically generated vertical alignment 
alternatives. The solution process took about 15 minutes. The 
most of the computation time was spent on calculating 
earthwork allocation using LP for each vertical alignment 
alternative. The time spent on earthwork allocation increases as 
the number intersection points along the roadway increase. 
Table 3. Total cost summary table 
  
Cost Components Costs ($) 
  
Total Construction Cost 
Road Specifications Values Earthwork Cost — 2109.09 
Construction Staking Cost 177.29 
Road width 4m Clearing Grabbing Cost 737.05 
Cut slopes 1:1 Drainage Cost 406.85 
Fill slopes 1.5:1 Seeding Mulching Cost 369.99 
Minimum curve radius 18 m Surfacing Cost 3221.65 
Minimum length of a vertical curve 15m Water Supply Watering Cost 859.87 
Minimum differences between grades 3% Riprap Cost 483.91 
Minimum road grade 2% Total Maintenance Cost 
Maximum road grade 16 % Rock Replacement Cost 319.45 
Minimum distance from road to streams 10 m Grading Cost 84.16 
Maximum cut and fill height at centerline 2m Culvert, Ditch, Brushing Costs 1060.62 
Design speed 55 km/hr Total Transportation Cost 1166.16 
  
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