The role of environmental effects in timber harvesting is deserving more importance in decision making and logging planning. Therefore more emphasise has to be put on planning system, so that environmentally sensitive sites for a certain harvesting system can be recognised and the best suitable machines selected for given terrain conditions. Some rut depth models based on WES-method have been developed for single pass rut and only a few for multipass. Forwarders usually have different wheel configuration and wheel load between axles, and the wheel load varies during a transport cycle. In order to test the suitability of some multicycle model in Nordic forestry conditions some test drives were organised and the rut depth after each wheel pass recorded. It was found out, that a multipass coefficient model using wheel numeric as the input variable and a simple multipass model gave acceptable results, but more tests are needed to test the total goodness of the method.

This paper includes some basic knowledge to be considered when discussing about the quality of work in harvesting wood and how to monitor it. This knowledge may aid to form an appropriate view on mechanised logging, environmental issues and trade of forest products. Many forest owners feel today, that leaving a good quality of work behind is the most important requirement set for logging machinery in the future. It is possible to present to the forest machine and equipment manufacturers some ideas on how to promote and influence the development of logging machines and equipment. This paper is partly based on a literature study, partly on theme interviews. Recent literature on productivity, machine and method studies on logging was examined from the quality of work point of view. Observations supporting an improvement in the quality of work were recorded. The idea was not to find out the level of the quality of work in practice as such, but to assess the relationships between the methods, machines and equipment used in respect to the quality of work. The interviews were conducted from May 22, 2000 to October 2, 2000 in Finland. The data consisted of six persons responsible for logging in a wood procurement district, six representatives of forest machine manufacturers and five logging contractors. A good quality of work in logging is characterised by doing it in an agreed way. Indicators for reaching the goals are evaluated by assessing the damages caused to the remaining trees, the rut formation, the strip road spacing and width, the way the thinning regimes are followed and the choice of trees to be cut. The target level is formed as a joint effect e.g. of efficiency in wood production, of credibility of mechanised operations, of considering the environment and of fluency in trade of forest products. Contributing factors to reach a good quality of work are the organisation of the logging, the forest machine operator as well as the machine and equipment technique. These factors may get a weighting value. However, the final result is a product of these factors, and all of them have to be considered. When looking at the situation today the human influence in logging, especially the role of the operator, is getting more emphasis. On the other hand, in the long run the possibilities to develop appropriate technologies are dominating, especially the use of new technologies. From the point of view of logging machinery the main factors affecting the work results, are the mobility of the vehicle, how to operate it and the work environment. In this paper, based on the development needs and possibilities, those aspects are looked at. An assessment of the present state is given and presents a basis for a more precise prediction of realistic targets. Based on a literature review and interviews conducted, it is possible to conclude, that there still is great potential to improve the quality of work in logging. Some direct technical improvements could promote the quality of work, but there are even some other actions, which indirectly through the operator would have a positive effect. An improved quality of work is often also improving the productivity in work. Furthermore it makes the organising of the logging operations easier and makes it possible to operate in a more demanding work environment even year around and 24 hours a day. The following is a list of research and development (R&D) needs concerning forest machinery, where inputs would be justified: • Better visibility (illumination, no dazzling, visibility) • Analysis of the CTI-system and eventual construction and testing of a test machine • The properties of tyres (width, diameter, tread, pressure) and their development • Control of the crane and its development (e.g. the automatic functions) • The role of a rotating cab on the operator, his productivity and the work result • Research into the role of levelling (seat, cabin, whole machine) • Steering of the machine (turning radius, “cutting” of corners) and possibilities to develop a vehicle with frame-steering and turning wheels • Research into the possibilities to utilise on-board weighing scales • Lighter machine construction • The role of tracks and comparison of different tracks • The role of a balanced boggie and its comparison with a single wheel • The role of the size of the harvester head on the operation control, work result and productivity • Possibilities to increase automation • Possibilities of work rotation and its effect on a normal logging system • The effect of a harwarder (harvester-forwarder) on the operator’s work

The increased awareness of environmental issues has created a need for evaluating the usefulness of mobility models for Nordic forestry conditions. A frame of reference based on the WES-method was used for developing empirical rut depth models for moraine forest sites. It was found that the penetration resistance in critical layers alone was an adequate soil input variable, even if the studied soils had very large variations in stoniness. When comparing the results with earlier models developed for organic soils, it was found that the same models apply for both types of soils. The method and models seem reliable enough for avoiding operations on too risky soils.