Productivity Models for Operational Planning of Timber Forwarding in Croatia

In the area of Croatian lowland forests, forwarders are usually used for extraction of timber assortments. Within the project »Systematization of norms for the production of timber assortments«, which was financed by the state company »Hrvatske šume« d.o.o. (»Croatian Forests« LLC), the process of development and implementation of new productivity norms for forwarders was carried out. Initially, for the execution of the research, it was necessary to gather data about technical characteristics of forwarders most frequently used in Croatia, but also around the world. The morphological analysis was performed and it was the basis for the classification of forwarders into classes. Three classes of forwarders were obtained after cluster analysis and load capacity appeared to be the most important factor. Machine performance was evaluated on 30 research sites. The standard method of time study (snap-back chronometric technique) was used. During the recording process, data of factors influencing forwarding (stand and terrain conditions) were collected. After analyzing the collected data, it was determined that the forwarding productivity depends on the forwarder class, average extraction distance, load characteristics, terrain and stand conditions. Regression analysis was used for identifying the time consumption of individual work components, and the productivity model for forwarding was developed. The obtained model was implemented into the application HsPPI. This is a part of the information system developed by IT Department of the state enterprise »Hrvatske šume« d.o.o. and is used for production planning in timber harvesting. The system is based on dBase IV databases and two main program modules. The main parts of the system are: tree marking data, assortment structure plan, production plan (felling, processing and extraction) and sales plan. Within a part of the production plan there is a module for calculating productivity norms for timber forwarding