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Forest road planning on aerial photographs, 
a new simple technique of road design in 
steep terrain 
by 
ir. J.M, Remeijn 
Department of Forestry, International Institute 
of Aerial Survey (ITC), Enschede, Netherlands. 
Introduction 
An increasing need for efficient forest management and optimum 
utilization of the forest resources requires careful planning of 
routes for access and transportation of manpower, equipment and 
forest products. 
There are several means of access available to the forester: 
- by air: low flying aircraft and helicopters provide a means for 
inspection and surveying, 
- waterways: rivers, canals and lakes are situated in the valleys 
and low plains. The transport is by boat, although timber is 
often drifted in logs or in rafts; The drifting in rivers is 
restricted to a one way direction, and is often subject to a 
seasonal pattern. 
- cable systems:allow transport up and down slope, 
- rail transport:can only be used in relatively flat terrain. 
- a road network:offers the best possibilities to open up a forest. 
It is less dependent of the topography than other systems, and 
serves the best the multiple purpose of forest management, inspect- 
ion, silvicultural activities, logging, fire control, pest control, 
recreation and communication (Le Ngoc Quy, 1971). 
Access by road 
An optimum access is especially important for the extraction of 
forest products. In timber exploitation and timber transport four 
main cost components are recognized (FAO, 1976): 
The cost of felling varies with the working conditions (weather, 
undergrowth, equipment) and the tree size. The expenses cover about 
2 to 13 percent of the total exploitation costs. 
Extraction costs includes the skidding from the stump to the road by 
horse, tractor or cable, and covers 16 to 48 percent of the total 
exploitation costs depending on the felling intensity and the terrain 
conditions (slope, soil type, undergrowth, swamps, etc.). 
Costs of the roadnetwork in the catchment area includes road construct- 
ion and maintenance and covers 7 to 34 percent of the total cost de- 
pending on the slope percent, road class and soil type. 
Truck hauling of the timber is good for 20 to 75 percent of the total 
cost of the timber exploitation. 
Since transportation costs are a major component in the expenses on 
harvesting operations, it is mainly this aspect that calls for a 
well documented road construction programme.