Previous Page Table of Contents Next Page


Walter Wolf1

1 Chief Logging Section, Forest Service Upper Austria, A-4020 Linz, Austria.


According to experts, in Austria another 15 000 to 20 000 km of forest roads will have to be built in order to achieve total accessibility of the forests. In the future, forest road construction will face increasing difficulties with regard to terrain and land ownership. This will require extensive studies and an assessment of alternatives to forest roads.

In this paper a new system of assessment based upon a valuation scheme is presented. It is divided into two groups: one that considers costs and one that considers non-monetary values. These two groups of criteria are equally important and, therefore, a maximum score of 50 is attributed to each. The fact that no forest road will be built can also be considered.

The financial analysis is based on the difference between production costs and earnings. The earnings from opening up a forest are derived from the sale of wood (less production costs) during the period of amortization of the forest road. The costs include the construction of the road, its maintenance, payments for the use of existing roads and expenses incurred by the forest workers and personnel to reach their workplace in the forest (travel costs). In order to facilitate a comparison, a simplified method for calculating the difference between costs and earnings has been developed. A certain number of values correspond to the difference between costs and earnings.

The group of non-monetary criteria includes ten different aspects. They consider the different effects forest roads have on the preservation of nature and landscape. The values are allocated according to the importance of the criteria. Within the criteria, the value depends on how close they meet the aim.

The total value determines which forest road is considered preferable. As the interval of the total value cannot be calculated by analytical methods, a limit of 5 percent has been fixed.

The system of the assessment together with the forms developed is given in the example.


According to the results of the National Forest Inventory (1986/1990), the Austrian forest land is well developed (approximately 135 000 km of forest roads, including effective public roads). Forest road densities differ depending on the various types of management and ownership systems (productive forests 45 m/ha, protective forests 9.5 m/ha, forest companies 30 to 40 m/ha and farm forests 50 to 70 m/ha). Experts estimate that approximately 15 000 to 20 000 km of forest roads will have to be built in order to achieve total accessibility of the wooded areas.

After having practically concluded the opening up of the area in question, there will be a big need for opening up of the remaining areas in the near future. This procedure is becoming more and more difficult because of increasingly complicated terrain, and very often lack of cooperation on the side of the landowners. All this requires a detailed planning which takes into account all interests involved in a project. Forest road projects must. above all, include the results of a study of alternatives conducted beforehand.

Objective procedures are essential for a comprehensive assessment of forest road alternatives. Various authors have examined this issue. The central problem in their works is inadequate consideration of non-monetary criteria of assessment (as for example the impacts on aesthetic values, and interference with ecologically valuable biotopes). Basic works have been conducted by Gundermann (1978) and Löffler-Timinger (1978).

Based upon these two studies, the author has developed a comprehensive and easy-to-apply method for the comparison of forest road alternatives. It is founded on a point system and also takes into account the zero-alternative (no construction of forest roads at all). The main features of this method are presented in this paper.

Assessment procedures

1. Method

The new method of assessment consists of two groups of criteria, namely:

· one group of monetarily quantifiable criteria; and
· one group of monetarily not or only hardly quantifiable criteria.

Gundermann (1978) found in his Delphi study, Die Beurteilung von Umwelteinwirkungen von Forststraßen im Hochgebirge, that these two groups are of equal significance. This remains valid even nowadays, if only the set of monetarily not or only hardly quantifiable criteria does not already predominate in its significance. Hence the new assessment procedure is based on the complete balance between the two sets of criteria (which can be regarded as secured) and a maximum value of 50 is attributed to each group. The benefit-cost difference is applied as a standard to the group of quantifiable criteria. The respective benefit-cost difference corresponds to a certain number of points.

The group of not or only hardly quantifiable criteria comprises the following ten criteria: the average distance between roads, steep terrain in the area of the construction line, switchbacks in steep terrain, geologically critical areas, rocky ground, biotopes worthy of protection, proximity of the construction line to water, visibility of the construction line, recreational function, and protective and beneficial function. These criteria also take into account the influences forest roads can have on matters of protection of nature and landscape. According to the importance of a criterion, the maximum score of points varies; if distance is the most significant criterion for quality in the planning of a forest road, it gets the maximum score of points. Within the individual criteria, the maximum score of points that can be reached depends on how closely they meet the aim.

The total number of points reached determines whether or not an alternative is favourable. The confidence interval of the total number of points cannot be calculated by analytical methods. Therefore, a limit of 5 percent has been set in order to be able to determine the difference between alternatives.

2. Catalogue of criteria

2.1 Quantifiable criteria of assessment (benefit-cost-difference)

The benefit of a forest road alternative results from the:

· total value of the discounted annual proceeds from the sale of timber, less the

· total value of the discounted annual costs for harvesting (felling and skidding) in the period of amortization.

The costs are made up by the

· costs for the construction of the new road (including payments for the use of existing forest roads); and the

· total value of the discounted annual road maintenance costs and travel expenses.

The benefit-cost difference demonstrates immediately the financial advantage of an opening-up alternative (Gundermann 1978). The rigorous procedure of calculating the benefit-cost difference is linked to a high cost in the field of data collecting. Therefore, a simplified procedure was developed for the relative comparison within a given opening-up area, a procedure that manages with easily collectable data. Costs and benefits are calculated for each alternative and referred to one hectare. The assessment procedure additionally assumes an even distribution of timber harvesting and the costs incurred (maintenance of the roads, travel expenses) within the entire period of amortization of the forest road.

2.1.1 Rigorous calculation of the benefit-cost-difference

As mentioned above, the benefit of a forest road is calculated as follows:

· discounted annual gross sales of timber (SVBE) within the period of amortization, less the
· discounted annual costs for harvesting (SV) within the period of amortization


The calculation of the discounted annual gross sale of timber (SVBE) within the period of amortization is demonstrated below:



rate of interest


present average proceeds for the timber from roads suitable for truck traffic roads in S/m3


calculated cut in the opening up area within the period of amortization in m3/year


expected average annual variation of the gross proceeds within the period of amortization in percent


period of amortization in years

For the exact determination of eH, k (present average costs for wood felling) and k (present average costs for wood skidding) it is necessary to ascertain the scheduled utilization of the stock within the period of amortization. The costs consist of:

· the costs for the construction of the new forest roads (NK), including payments for the use of existing roads, and the

· discounted annual road maintenance costs (SVWe), as well as the

· discounted annual travel expenses (SVAw)

K = NK + SvWe + SVAw

2.1.2 Simplified model for the calculation of the difference between costs and earnings

Road maintenance costs and travel expenses, as well as earnings, are calculated as the discount of an everlasting annual rent at an interest rate of 4 percent (capitalization factor 25). Hence the following calculation scheme:


Construction costs in S/ha (= S/m x m: ha)


+ Maintenance in S/ha (= S/m/a x in x 25: ha)


+ Travel expenses in S/ha (= S/m3 x m/ha/a x 25)


+ Payments for the use of existing roads in S/ha


= Total cost in S/ha


Benefit in S/ha (proceeds free from harvesting costs)
(m3/ha/a x S/m3 x 25)


Benefit-cost difference = (6) - (5)

For relative comparisons, it is sufficient to take into account the average conditions when calculating the expenses. In this context reference is made to investigations carried out by Abegg (1988) (Table I):

Table 1. Travel expenses in S/m3 for forest workers and other personnel depending on road density and skidding technique for average slope grades (50%)

(derived from Abegg 1988)

Skidding technique/Road density (m/ha)











Forest road and (mobile) cable systems






Forest road and skid road











In the simplified procedure the benefit (proceeds free from harvesting costs) of opening up a forest is determined as follows:

Starting point is average proceeds from the sale of timber of S 800/m3. The average felling costs are determined with S 120/m3. In order to determine the average skidding costs, it is necessary to fix the skidding technique (for example mobile cable systems for skidding distances > 300 m; gravity skid) for each section of the opening area. The average skidding distance for these sections (use easiest possible geometrical shapes for an easy surface calculation) is read from the site plan. With the help of Table 2, one can ascertain the average skidding costs for each section. The area-weighted arithmetical mean of these skidding costs result in the average skidding costs of the opening-up area. Just as Table 1, Table 2 only considers average conditions, which is sufficient for relative comparison.

Table 2. Skidding costs in S/m3 for different skidding techniques depending on skidding distance (derived by Abegg 1988); d = skidding distance in m

Skidding technique

Broadleaved forests

Coniferious forests

Tractor ground skid

188,1 + 0,36 d

107,8 + 0,22 d

Tractor on skid road

245,5 + 0,36 d

145,7 + 0,27 d

Winching uphill

2,98 d

1,95 d


5,85 d

3,78 d

Gravity skid



Cable yarding uphill

385,4 + 0,25 d

254,6 + 0,33 d


370,5 + 0,70 d

325,7 + 0,24 d

2.1.3 Attribution of points

Following Figure 1, points are attributed to the benefit-cost difference. In order to delineate the range of values for the benefit-cost difference, we assume a coppice forest and a coniferous forest and take into account average road construction and maintenance costs. Even for the zero-alternative (no forests roads constructed) the attribution of points is effected by means of the calculated benefit-cost-difference. In most of those cases, travel costs are of great weight. At the same time, long skidding distances often result in low proceeds free from harvesting costs. In the majority of cases, this leads to negative benefit-cost differences.

Figure 1. Attribution of values for the group of monetarily quantifiable criteria 2.2 Not or only hardly quantifiable criteria of assessment

Average switchback or road distance

Depending on the size of a property, the following average road distances are regarded as being optimal for the circumstances prevailing in Austrian alpine forests; in each individual case it is necessary to adapt to local terrain conditions and to available skidding techniques.

Table 3. Objective average road distance in the different properties of Austrian alpine forests (Sedlak 1985)

Large private forests (>5000 ha)

400-600 m

Average private forests (1000 -5000 ha)

300-400 m

Small private forests (200 - 1000 ha)

250-350 m

Farm forests

200-300 m

In order to be sufficiently successful in any opening up, the minimum switchback distance in small private and farm forests should not be less than 700 to 800 m.

Steep terrain in the area of the construction line

The construction of forest roads in extremely steep terrain is highly problematic, as the masses to be moved increase progressively of the same amount as the inclination of the slope. From a slope grade of approximately 65 to 70 percent and above, one must at least face surplus material originating from the propulsion of the construction line, as it is impossible to build stable embankments (fill slopes). The resulting high slopes which, especially in rocky terrain, hardly ever grow in, could cause tremendous disarrangement in the countryside for years. It is, however, possible to reduce the interference by limiting the width of the sub-base to the minimum size needed to ensure that trucks can use the road without any risk (4 m in steep rocky terrain). In this assessment procedure, a steep rocky terrain is defined as an area with an inclination exceeding 70 percent.

Switchbacks in steep terrain

Additional opening up should, wherever possible, link up with existing forest roads. Winding roads only on the owners' land should be avoided. In any planning it is most important to succeed in reaching an optimal opening up with a minimum of switchbacks. In many cases, however, suitable places for switchbacks, like stable intermediate ridges or flat areas in the terrain, are most important for the road system on difficult terrain. Sedlak (1982, 1993) suggests not building switchbacks at locations exceeding 40 percent. In steeper terrain, the building of switchbacks causes outstanding costs. In rocky terrain, switchbacks on steep terrain are regarded as severe wounds to the landscape if they cannot be sufficiently shielded by wooded areas. If switchbacks on steep terrain cannot be avoided, there should only be an expansion for solo-trucks (minimum radius of switchback 8 m).

Geologically critical areas

In the planning of forest roads in the past, sufficiently careful consideration has not been given to the ground. Several cases of landslide give testimony of this fact. Various geological formations (e.g. Flysch) are known to be highly prone to sliding. But even when dealing with rocky ground, stability problems cannot be totally avoided due to the existing structure within the rocks. Especially in this case, almost irreparable wounds to the landscape are likely to be caused by landslides. Consequent damages can only be excluded through thorough planning. Therefore, it is extremely important to take into account all kinds of geotechnical particularities of a given area.

Rocky ground

Construction lines with a high percentage of rocky ground usually take very long to grow back into the landscape. Sunny sites are most difficult to revegetate. Such forest roads can cause long-lasting disarrangement of the landscape.

Biotopes worthy of protection

As a matter of principle, springs, bigger areas of humidity, characteristic rock formations, remaining natural woods, moorland and edges of forests are negative cardinal points for the construction of forest roads. As a result, these kinds of biotopes have to be taken into account in the planning. If biotopes worthy of protection cannot be avoided, it is necessary to take the appropriate measures to ensure minimal consequences.

Proximity to water

The transition zone from water to ground is ecologically highly sensitive. When valley roads are concerned, the brook might need insertions in order to secure the road. Valley roads should, therefore, be conducted high-water free at a distance of at least 10 to 20 m to the watercourse (Sedlak 1993). The overgrown banks of the rivulet serve as a buffer zone. Sections where watercourses cross the forest road are very sensitive spots. Culverts are not desirable for ecological reasons, but are sometimes inevitable for financial reasons. Constantly flooded fords are less problematic with regard to their influence on the ecology of the watercourse; they cannot be recommended though for main roads (bad driving conditions). Bridges would be most suitable from an ecological and technical point of view, but they are financially not practicable when it comes to tiny watercourses. The area, which is commonly defined as being in immediate proximity to water, is an area of 20 m at both sides of the watercourse.

Visibility of the construction line

Longer and widely visible parts of the construction line are felt as being inconvenient. Quite frequently, construction lines which are originally well shielded by means of already existing wood stock are destroyed and exposed by inconsiderate clear-cuts across the road. Clear-cut areas and juvenile woods immediately underneath the construction line cannot protect the new construction from being visible. Older stocks of coniferous trees are best suited in this case. Deciduous trees and larches let shine through the construction line in winter. Roads which run across open spaces (e.g. alpine pastures) are (in most cases) widely visible, too.

Recreational function of the area in question

If an area has an important recreational function, a highly preserved and cared-for nature is of eminent importance for the visitor. Following recent research, mere hiking paths have received a higher recreational value than forest roads or skidding paths (Löffler-Timinger 1978). A high recreational function is prominent in wooded areas in the immediate surroundings of big cities and in areas where tourism is of great importance all year round. Wooded areas, which are hardly frequented by visitors longing for recreation, have a low recreational function. The rating from 1 to 3 appearing in the WEP (Forest Development Plan) can be adopted directly.

Protective and beneficial function

Quite often, the securing and/or rehabilitation of the protective function of woods (avalanches, erosion, rock slide) call for an at least minimal opening up by means of forest roads, as otherwise indispensable measures could not be taken or financed. In forests with an additional function as a protection forest for objects, such measures are, in most cases, given priority. The protective effect is not considered as secured in the assessment of alternatives, if measures are absolutely necessary within the following ten years. A high beneficial function (e.g. a well-balanced supply of drinking water) can be only maintained in most cases by taking intensive care of the forest. Untapped forest areas with a high beneficial function are therefore given two points in the assessment.

2.2.1 Attribution of values

The attribution of values for the different criteria is shown in Table 4. In the zero-alternative, the set of monetarily not or only hardly quantifiable criteria is given 40 points, as it could be linked to ecologically negative consequences (e.g. damage to the remaining stock, erosion, extensive clear-cuts).

Table 4. Attribution of values for the group of not or only hardly quantifiable criteria


Dimension of the criterion


Distance between switchbacks (farm forests)

< 400 m


400 - 500 m


500 - 600 m

4 7

600 - 700 m

700 - 800 m


> 800 m


Distance between roads (farm forests)

< 100 m


100-200 m


200 - 300 m


300 - 400 m


> 400 m


Steep terrain > 70%
(% of road length)

< 5%


5- 10%


10- 15%




20 - 25 %


> 25 %


Switchback (s) in steep terrain > 40%





Geologically critical areas
(% of road length)

< 1 %


1 - 2 %


2 - 3 %


3 - 4 %


> 4 %


Rocky ground
(% of road length)

< 10 %




20 - 30 %


30 - 40 %


> 40 %







Proximity to water
(% of road length)

< 5%


5- 10%




20 - 30 %


30 - 40 %


> 40 %


Visibility of the road
(% of road length)

< 10 %


10-20 %


20 - 30 %


30 - 40 %


40 - 50 %


> 50 %


Recreational function







Protective and benefical function



not assured


Example (additional opening-up project Haider-Hainzl)

The mostly steep and north-sided slope possesses a mixed stock of deciduous, as well as coniferous, trees of all age groups. The opening up of the forest is almost finished. Only the northeastern part of the slope requires further opening up. The distance between the valley road and the existing forest road amounts to a maximum of 600 m. In this area, the farthest-off part of the slope is tractor-trafficable at a length of approximately 100 m uphill; otherwise, the skidding of the wood must be carried out by hand or by means of a winch or cable system. The delimitation of the area to be opened up is shown in Figure 2. It covers 27 ha.

Figure 2. Site plan of the opening-up alternatives

Two alternatives have been developed. The alternative Uferer sets a construction line branching off from the valley road and showing a maximum gradient of 11 percent. An outside lot must be crossed between 600 m and 730 m. The inclination in the area of the construction line is between 35 and 55 percent. The road is 1325 m long. At about 50 m, rocky ground is expected. At 180 m the projected construction line would cross a torrent (not permanently carrying water) with adverse gradient. The projected road would lead through an area of juvenile wood and, therefore, be visible at a length of about 200 m.

The alternative Haider branches off the already existing forest road at approximately 1100 m and declines with 9 percent adverse gradient as far as 560 m and afterwards ascends with about 10 percent until it reaches the eastern boundary of the property. In this alternative, the outside lot is crossed. Originally, this alternative was developed because the two landowners would not cooperate. The construction line is approximately 980 m long. At about 300 m, rocky ground is expected. At about 170 m, it touches steep terrain with an inclination higher than 70 percent. Additionally, a 65 percent steep slope is crossed at a length of about 300 m. The construction line leads through deciduous forest and juvenile wood for about 400 m.

The benefit-cost difference is calculated with the help of the simplified model (Figure 4). The average skidding costs are determined as area-weighted arithmetical mean of the average skidding costs in the different sections of the opening-up area (Figure 3 and Table 5). The delimitation of the sections is made by taking into account the skidding method planned for each part of the area. The average skidding distance for each section is read in the plan; the average skidding costs can then be calculated with the help of the formulas in Table 2. The proceeds free from harvesting costs amount to S 442 (S 800 less S 120 less S 238). The data needed for the assessment of both alternatives are shown in Table 6.

Figure 3. Site plan for the calculation of the average skidding costs (alternative Uferer)

Figure 4. Calculation of the difference between costs and earnings (simplified model)

Table 5. Calculation of the average skidding costs (alternative Uferer)

Section Skidding technique


Average skidding distance

Skidding costs

1 Gravity skid




2 Winching uphill




3 Gravity skid and tractor on skid road


39 Gravity skid 350 Tractor


4 Gravity skid and tractor ground skid


78 Gravity skid 65 Tractor


5 Gravity skid and tractor ground skid


52 Gravity skid 78 Tractor





Table 6. Data for the assessment of the alternatives


Alternative Haider

Alternative Uferer

Construction (m)



Opening up area (ha)



Construction costs (ATS/m)



Maintenance (ATS/m/year)



Sale of timber less harvesting costs (ATS/m3)



Annual increment (m3/ha/year)



Payments for the use of existing roads (ATS/ha)



Average distance between roads (m)



Steep terrain > 70% (m)



Switchback (s) in steep terrain



Geologically critical areas (m)



Rocky ground (m)






Proximity to water (m)



Visibility of the road (m)



Recreational function



Protective and benefical function



The result of the assessment for the alternative Uferer is shown in Figure 5, it gets 62 points. The alternative Haider only gets 44 points. The alternative Uferer, which is clearly more protective with regard to the landscape and more effective for opening up outclasses the alternative Haider, in which no outside property is needed.

Figure 5. Result of the assessment (alternative Uferer)


Abegg, B. 1988. Wirtschaftliche Erschließung von Wäldern in Hanglagen - Entscheidungsgrundlagen zur Beurteilung von Erschließungsvarianten. (Eidgenössische Anstalt für das forstliche Versuchswesen, Birmensdorf, Bericht Nr. 302)

Gundermann, E. 1978. Die Beurteilung der Umwelteinwirkungen von Forststraßen im Hochgebirge. Forschungsbericht der Forstlichen Forschungsanstalt. München 41/1978.

Löffler, H. & Timinger, J. 1978. Nutzen - Kosten - Untersuchung über den forstlichen Wirtschaftswegebau. Landwirtschafangewandte Wissenschaft Heft 202. Landwirtschaftsverlag Münster-Hiltung)

Sedlak, O. 1982. Types of roads and road network under difficult mountainous conditions and its relation to operational cable systems. ECE/FAO/ILO Proceedings. Sandefjord, Norway.

Sedlak, O. 1985. Mountain forest roads in rural communities of Alpine Central Europe. IX World Forestry Congress. Mexico.

Sedlak, O. 1988. Forest development in Austria. IUFRO Workshop. Fiesch, Switzerland.

Sedlak, O. 1993. Forststraßenbau und Naturschutz. Österreichische Forstzeitung 7/1993

Wolf, W. 1994. Variantenvergleich im Forststraßenbau. Dissertation. Universität für Bodenkultur Wien. Institut für Forsttechnik.


m = metre
ha = hectare
S = shilling

Previous Page Top of Page Next Page