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14. THE IMPACT OF TIMBER HAULAGE ON LOADING
OF FOREST ROADS
Grzegorz Trzciński & Waldemar Sieniawski
Warsaw University of Life Sciences-SGGW, Faculty of Forestry, Department of Forest Utilization,
Warsaw, Poland
Grzegorz_Trzcinski@sggw.pl, Waldemar.Sieniawski@wl.sggw.pl
Introduction
The significance of proper timber haulage, and primarily organizing appropriate road network, has
been emphasized since XIX century, where C.A. Schenck (1911) briefly defined the issue:
„Indeed, it might be stated, that forestry is essentially a problem of transportation”. Costs incurred
by the forestry enterprise to build and maintain a network of forest roads are a significant part, and
are often the biggest cost of operating the forestry. From data of the General Directorate of State
Forests in Poland (PGL LP) in 2007 for the construction, renovation and maintenance of road
infrastructure earmarked 330 million PLN - 6.3% of total costs (84.93 million Euro). Among the
costs associated with maintenance of road infrastructure and providing adequate technical quality,
a significant part are the costs arising from the conditions of the project in differentiated
physiographic conditions, and particularly to ensure the proper construction of forest road
pavements.
Defining the road’s load is associated with quantitative and qualitative analysis of traveling
vehicles. On its basis it is possible to obtain data necessary to determine the axle load
equivalency factors. Vehicles with a greater number of equivalent standard axles is characterized
by an increased impact on the surface of the road. Number of researchers were engaged in
determination of traffic and its structure resulting from the destination and types of vehicles driving
on forest roads. Optimization of timber haulage in load capacity context and resulting gross
vehicle weight GVW (car with trailer) were involved, Hamsley, Devlin and McDonnell. Overloading
has an impact on forest road surface and accelerates its degradation, leading to the absence of
proper timber transport.
Most of 32 million m3 timber harvested In Poland is being moved from place where is harvested
and collected in forest directly to recipient or in place of handling (rail, depot handling) by road
transport. This means that forest roads are exposed to high tonnage vehicles, often exceeding the
GVW limit, what in effect gives load on the axis of the vehicle above the accepted design
parameters and is the cause of accelerated degradation of the forest road.
Weight of timber load is a very variable feature. Vehicles are often overloaded and identifying
GVW on the base of technical parameters of truck and weight of load calculated from number of
m3 is highly inaccurate. The objective of this work was to examine the actual loads on the forest
road from vehicles used for timber exports, resulting from the gross vehicle weight (GVW) as the
sum of its own empty truck weight and trailer and load and the simultaneous distribution of
pressure on vehicle axles.
Material and methods
As a place of study we selected the two major recipients of wood from the area of the northern
Poland: first – accepting daily approximately 800-1000 m3 of pine logs (WC0) and the second -
receiving 2000-4000 m3 of medium-sized material (S2) of various species. All the timber is
delivered by high-tonnage trucks.
On the handling area, using gravity measurements, we made weight controls of every truck going
in – GVW, and every truck going out – empty set weight. The difference between full and empty
vehicle gave weight of load. The volume of timber transported in m3 was determined by a receipt
issued by the seller. Measurement of load on each axle of high-tonnage vehicle has made using a
mobile platform scale, where the weight of single wheel axle was determined. The hypothesis that
differences in obtained results GVW and volume of timber transported between the various types
of cars and the size of the load for a given set of axes are statistically significant has been tested
by analysis of variance. Regression model of the GVW and the weight of load, depending on the
load (in m3) of transported wood, has also been calculated.
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