net- 
the 
rucks, 
road. 
cks, 
ry of 
rans- 
~ 0 
[2 
ters, 
akes, 
po- 
| width 
apacity. 
The required density of the road network is determined by the tyve 
and intensity of the forest management, the tree species composit- 
ion, the age class distribution and the logging intensity. Also the 
type of t.rrain has influence on the road density; factors of import- 
ance are the ruggedness of the terrain, the drainage system and the 
steepness of the slopes. 
The actual road density is closely related to the infrastructure of 
a region. In India the forest road density is 3.5 m/ha on the average, 
but knowing that the majority of the roads are located in the well 
populated areas, it will be clear that the Indian forest in general 
are not well opened up (Chandra, 1976). An other extreme is the 
Kobernausserforest in Austria, where with its intensive management of 
highly productive spruce forests the average density of all weather 
roads is between 30 and 35 m/ha. 
Other decisions deal with the maximum alowable road gradient, the 
radius of the curves, the road width and the bearing capacity. They 
all depend on the intended use of the road system (Samset, 1967). 
Road curves must have a radius not smaller than 40 m. for long 
vehicles in flat .terrain. In steep terrain the radius is often as 
small as 25 m. 
The maximum gradient of the roads is depending on the type of 
transport. Unloaded tractors can manage to go uphill on sloves 
up to 40 %, but when loaded or skidding timber they should not 
come on roads steeper than 20 to 25 percent. Often a limit to the 
maximum gradient is set by the type of soil. Due to the danger of 
erosion the roads in Austria are constructed with a cradient not 
steeper than 12 percent, while in Cyprus the maximum is 8 percent. 
Photo interpretation 
In addition to the topographic maps,that usually are available 
also existing aerial photography of the area provides much inform- 
ation, and their study is then strongly recommended. The advantace 
of aerial photographs over topographic maps is that they contain 
details about the soil type, drainage system, swamps, landslide 
sensitive areas, and other obstacles such as rock outcrops, cliffs, 
powerlines, houses, etc., that are not well shown in the maps. 
A trained photo.interpreter can tell the road planner much about 
the land use and the composition of the forests. He also may indicate 
possible deposits of road building material like gravel, and suitable 
points for a bridge to cross a river. Photo interpretation therefore 
plays a large role in the reconnaissance phase of the road planning 
(Hallert, 1976, and Waelti, 1970). 
Flow diagram 2 demonstrates how the procedure in road planning 
runs from the collection of basic information via the interpret- 
ation of small and large scale aerial photographs to the last 
stage of the actual construction of the proposed road.