Evaluation of stress loading for logging truck drivers by monitoring changes in muscle tension during a work shift

Our research aimed to quantify and evaluate the stress loading of drivers by monitoring the loading of the radial extensor muscle at the wrist joint (musculus extensor carpi radialis) when they drove different types of timber trucks. We monitored changes in the electric potential of skeletal muscles with electromyographic measurements and measurements of changes of heart rate using the Biofeedback 2000 x-pert device. The drivers were observed throughout their work shifts during normal operation of logging trucks and logging trucks with trailers. As a reference, muscle load was measured when driving a passenger car. We evaluated the normality of the measured data and obtained descriptive statistics from the individual measurements. The differences in stress load associated with driving the different types of vehicles increased whilst driving on lower-class roads. Results showed a high stress load for drivers of loaded vehicles when driving on narrow roads. It was more challenging to control a loaded logging truck with a trailer than driving a logging truck, with the difference in muscular loading reaching 22.5%. Driving a logging truck with a trailer produced 46.5% more muscle loading compared to driving a loaded passenger car. For preventive health and safety reasons, it would be reasonable to alternate between drivers when operating various vehicles, thus minimizing the development of possible health issues

Double Bark Thickness Estimation Models of Common European Broadleaved Species for Harvester Timber Volume Estimation in Czechia

The share of the annual volume of harvester-produced timber in Czech forest bioeconomy has increased in the last decades. To estimate under-bark timber volume, harvester systems allow choosing between two different bark deduction models – diameter band (DBM) and linear model. However, linear models were not calibrated for the conditions of Czech forestry. Therefore, the objective of this research was to develop, for local conditions in Czechia, linear functions for estimating the double bark thickness of two groups of broadleaved species (beech and oak) and to test their viability based on real harvest data. To create the linear functions, official Czech cubing tables were used. Data from real harvests were gathered from fifteen harvesters. A sample containing 4995 logs belonging to the beech group was analyzed using descriptive statistics and the Paired Wilcoxon tests. The mean double bark thickness for beech group was 15.1 mm (polynomial and linear model). For oak group, it was 15.48 mm (polynomial) or 15.49 mm (linear). The results of real harvests for beech group revealed that the mean double bark thickness estimated by the polynomial function was 7.08 mm. The linear function estimates were closer to the value estimated by the polynomial (6.84 mm) than DBM estimates (6.68 mm). Therefore, we can state that the newly developed linear models can be used in fully mechanized harvesting instead of manual bark deduction methods in Czechia

The Effect of Different Road Types on Timber Truck Drivers by Assessing the Load Environment of Drivers by Monitoring Changes in Muscle Tension

Our research aimed to quantify stress load in drivers by monitoring the load on the radial extensor carpi radialis (musculus extensor carpi radialis) on different types of forest and other categories of roads. We observed changes in the electrical potential of skeletal muscles using electromyographic measurements and changes in heart rate using a Biofeedback2000 x-pert recorder. We measured the loading of drivers during the normal operation of timber trucks and timber trucks with trailers, while the reference measurements took place in a passenger car. We obtained descriptive statistics from the individual measurements and evaluated the normality of the measured data. Differences in muscle load increased when driving on lower-grade roads. The muscle load increased significantly, especially when passing through villages, inversely proportional to the width of the roads and the radius of their bends. Experiments revealed that the drivers of loaded vehicles who drove on lower-grade roads were under higher stress. Muscle load of drivers a loaded timber truck with a trailer was more difficult on roads of lower grades than on roads of grade I by 41.3%. Driving a timber truck is 21.9% more difficult on lower grade roads than on grade I roads. For preventive health and safety reasons, it is optimal to alternate trucking with a different type of work, thus minimizing the chance of occurrence of health disabilities

The Effect of Different Road Types on Timber Truck Drivers by Assessing the Load Environment of Drivers by Monitoring Changes in Muscle Tension

Our research aimed to quantify stress load in drivers by monitoring the load on the radial extensor carpi radialis (musculus extensor carpi radialis) on different types of forest and other categories of roads. We observed changes in the electrical potential of skeletal muscles using electromyographic measurements and changes in heart rate using a Biofeedback2000 x-pert recorder. We measured the loading of drivers during the normal operation of timber trucks and timber trucks with trailers, while the reference measurements took place in a passenger car. We obtained descriptive statistics from the individual measurements and evaluated the normality of the measured data. Differences in muscle load increased when driving on lower-grade roads. The muscle load increased significantly, especially when passing through villages, inversely proportional to the width of the roads and the radius of their bends. Experiments revealed that the drivers of loaded vehicles who drove on lower-grade roads were under higher stress. Muscle load of drivers a loaded timber truck with a trailer was more difficult on roads of lower grades than on roads of grade I by 41.3%. Driving a timber truck is 21.9% more difficult on lower grade roads than on grade I roads. For preventive health and safety reasons, it is optimal to alternate trucking with a different type of work, thus minimizing the chance of occurrence of health disabilities

Estimation of Over- and Under-Bark Volume of Scots Pine Timber Produced by Harvesters

Harvesters produce one third of timber in Czechia. The aim of this study was to analyze the over- and under-bark volume estimates of Scots pine (Pinus sylvestris L.) timber produced by a mid-performance harvester. The data were collected between March 2017 and June 2018. In total, 4661 stems cut into 29,834 logs were analyzed. For volume estimation, StanForD offers several price categories using various algorithms. Three of these price categories are relevant for Czech forestry—M3s, M3toDE, and M3miDE. The M3s price category is based on the estimation of partial volumes of 10 cm long sections, which are summed. Therefore, this price category represents the volume estimation closest to the true volume. By comparison, the M3toDE and M3miDE price categories use the same algorithm for volume estimation, which is based on the Huber formula using a midspan diameter rounded down to the nearest whole centimeter. The M3toDE price category underestimated the over-bark volume by 6.48% compared to the reference price category M3s. The mean log volume estimated through the M3s price category was significantly higher than the M3toDE volume both in individual grades and without grading. We found significant differences between under-bark volume estimates by the diameter band bark deduction method (DBM) and the parametric linear bark deduction method (PLM) used in harvester’s systems according to the Guidelines for Electronic Scaling of Timber for Harvesters in Czechia (GEH) for Scots pine butt logs with rough bark, and also for other logs with normal bark thickness. To obtain under-bark volume estimates of Scots pine timber that are comparable with the Guidelines for Timber Scaling in Czechia (GTS) using the parametric nonlinear bark deduction method (PNM), we recommend using the algorithm of the M3toDE price category, with double bark thickness determined by the diameter band bark deduction method

Differences in Timber Volume Estimates Using Various Algorithms Available in the Control and Information Systems of Harvesters

Timber is the most important source of revenue in forestry and, therefore, is necessary to precisely estimate its volume. The share of timber volume produced by harvesters is annually growing in many European countries. Suitable settings of harvesters will allow us to achieve the most accurate volume estimates of the produced timber. In this study, we compared the different methods of log volume estimation applied by control and information systems of harvesters. The aim was to analyze the price categories that can be set up in the StanForD standard and to determine the differences between the algorithms used for log volume estimations. We obtained the data from *.STM files collected from March 2017 until June 2018 on a medium-size harvester. We analyzed price categories and found seven different algorithms used to estimate the log volumes. Log volume estimates according to Algorithm A2 were considered as standard because these estimates should be closest to the true log volumes. Significant differences, except the difference between Algorithm A2 and Algorithm A3, were found between log volumes estimated by different algorithms. After categorization of logs to assortments, the results showed that significant differences existed between algorithms in each assortment. In the roundwood assortment, which contains the most valuable logs, a difference of more than 6% was found between the log volumes estimated by Algorithm A5 and Algorithm A2. This is interesting because Algorithm A5 is widely used in some Central European countries. To obtain volumes closest to the true volumes, we should use Algorithm A2 for the harvester production outputs. The resulting differences between the algorithms can be used to estimate the volume difference between harvester outputs using the different price categories. Understanding this setting of harvesters and the differences between the price categories will provide users useful information in applied forest management

Operational Costs of Mid-Performance Forwarders in Czech Forest Bioeconomy

Cut-to-length (CTL) operations are expanding in Central European bio-economies. However, they are costly, so efficiency must be maximized. The objective of this study was to analyze direct operational costs of three forwarders from the year 2006 until 2019. Annual amortization, services, materials, and personnel costs were analyzed and compared through ANOVA, trends were analyzed through linear regression. Forwarders LVS 5, John Deere 1010, and John Deere 1110E were deployed in coniferous forest stands with a mean stem volume between 0.10 and 0.84 m3/stem, forwarding distance between 261 and 560 m. The machines forwarded between 4045 and 34,604 m3 of timber per year, over operational times between 490 and 3896 MH (machine hours)/year, reaching machine utilization between 58% and 89%, machine productivity between 3.5 and 12.3 m3/MH, and costs between 20.95 and 84.39 €/MH. The most substantial were personnel costs (35 to 66% of the total costs), followed by materials (14.9–27.1%), amortization (12.5–15.7%), and services (3.3–22.1%). Differences between total operational costs per m3 of machines with different engine powers were not observed