Development of Updated Models to Characterize Skidding Performance in Romania Based on a Nation-Level Dataset
Abstract
1. Introduction
2. Materials and Methods
2.1. Study Locations and Machine Types
2.2. Data Collection
2.3. Data Processing
2.4. Statistical Analysis
- The variables of elemental time consumption (tDET, tMAN, tPOC, tAPL, tPIP, tDPC, tAPE, tDFR, tDPR, tMBR, tDS, tDP, tDM, tDO, converted in hours), cycle time consumption (tSWC, h), fuel consumption (FC, L), payload volume (PV, m3), number of pieces (NP), and extraction distance (ED, m) were checked for normality using the Shapiro–Wilk test;
- To characterize the data, descriptive statistics were calculated and reported for these variables, including minimum and maximum values, range, mean, and median values;
- Cycle time (CT, h) and fuel consumption (FC, L) models were developed using multiple linear regression techniques, ensuring that initial assumptions of multi-linear regression were met, as well as that the developed models were significant globally while retaining the statistically significant predictors. The initial assumptions included:
- The existence of a linear relationship between the dependent variables (time or fuel consumption) and the independent variables, which was preliminary checked by scatter plots;
- Multivariate normality (i.e., normal distribution of residuals, which was checked by rigorous tests—Shapiro–Wilk, histograms, and boxplots);
- The absence of multicollinearity (no significant correlation between independent variables, using a correlation threshold of 0.8, which was checked by a correlation analysis based on a correlation matrix); and
- Homoskedasticity (i.e., ensuring the variance of residuals was consistent across all levels of independent variables, which was checked by rigorous techniques, i.e., Breusch–Pagan and White tests).
2.5. Modeling of Efficiency, Productivity, and Unit Fuel Use
3. Results
3.1. Descriptive Statistics of Operational, Time and Fuel Consumption Variables
3.2. Time and Fuel Consumption Models
3.3. Efficiency, Productivity and Unit Fuel Consumption Models
4. Discussion
5. Conclusions
Author Contributions
Funding
Data Availability Statement
Acknowledgments
Conflicts of Interest
Appendix A
References
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Study Site | Machine Type | Season | Trail Condition | Type of Forest | Number of Observed Work Cycles |
---|---|---|---|---|---|
SK1 | Skidder | Winter (November) | Moist | Mixed | 16 |
SK2 | Skidder | Autumn (September) | Moist | Mixed | 10 |
SK3 | Skidder | Winter (November) | Moist | Coniferous | 20 |
SK4 | Skidder | Winter (November) | Moist | Mixed | 14 |
SK5 | Skidder | Winter (November) | Moist | Mixed | 2 |
SK6 | Skidder | Winter (November) | Moist | Mixed | 19 |
SK7 | Skidder | Spring (March/May) | Moist | Mixed | 29 |
SK8 | Skidder | Spring (March/May) | Moist | Mixed | 59 |
SK9 | Skidder | Summer (August) | Dry | Broadleaved | 32 |
SK10 | Skidder | Summer (July) | Dry | Broadleaved | 23 |
SK11 | Skidder | Summer (July) | Dry | Broadleaved | 30 |
SK12 | Skidder | Summer (August) | Dry | Broadleaved | 53 |
FT1 | Farm tractor | Autumn (September/October) | Moist | Broadleaved | 85 |
FT2 | Farm tractor | Summer (August) | Dry | Broadleaved | 32 |
Task Name | Task Code | Time Consumption Code | Description |
---|---|---|---|
Driving to the pre-skidding site | DET | tDET | Started when the machine leaves the landing area and ended when it arrives at the pre-skidding site. It occurred in all skidding work cycles and excluded any interruptions. |
Maneuvering at the pre-skidding site | MAN | tMAN | Started when the machine arrived at the pre-skidding site and ended when it was positioned for pre-skidding. It occurred in most of the skidding work cycles, excluded any interruptions, and included maneuvers performed outside the skid trails. |
Pulling out the cable | POC | tPOC | Started when the driver released the cables and one or more workers started moving with the cables to the wood pieces to be attached and ended when the worker(s) arrived at the pieces of wood. It occurred one to several times in all skidding work cycles and excluded any interruptions. |
Attachment of the payload | APL | tAPL | Started when the worker(s) arrived at the wood pieces to be attached and ended when the wood pieces were attached to the cable(s). It occurred one to several times in all skidding work cycles and excluded any interruptions. |
Pulling in the payload | PIP | tPIP | Started when the driver operated the winch to pull in the payload and ended when the payload reached the rear of the machine. It occurred one to several times in most of the skidding work cycles and excluded any interruptions. |
Detaching the payload from the cable | DPC | tDPC | Started when the worker(s) started to move towards the payload and ended when the payload was detached from the cable(s). It occurred one to several times in most of the skidding work cycles and excluded any interruptions. |
Attaching the payload for extraction | APE | tAPE | Started when the cable(s) is released and ended when the payload was secured for extraction. It occurred in most of the skidding work cycles and excluded any interruptions. |
Driving with the payload to the forest road | DFR | tDFR | Started when the machine engaged in driving loaded to the forest road and ended when it reached the place for payload detaching at the forest road (landing). It occurred in all the skidding work cycles and excluded any interruptions. |
Detaching the payload at the forest road | DPR | tDPR | Started when the driver started to lower the payload and ended when the worker detached the cables. It occurred in all the skidding work cycles and excluded any interruptions; sometimes the payload was released without the assistance of manual worker. |
Maneuvering and bunching at the forest road | MBR | tMBR | Started with the first maneuver to group wood and ended once the wood pieces were bunched at the required place at the landing. It occurred in most of the skidding work cycles and excluded any interruptions. |
Skidding work cycle | SWC | CT | Groups all of the above work elements as they occurred and/or repeated between starting to move from the landing and completing the maneuvering and bunching at the forest road. It excluded any interruptions. |
Delays caused by the study | DS | tDS | Delays attributable to the tasks of the researchers carrying out the study, such as placing and taking down the dataloggers, measuring the fuel consumption and/or the biometrics of the wood. Most of them occurred at the landing. |
Delays caused by personal reasons | DP | tDP | Delays caused by personal activity of workers. |
Delays caused by mechanical reasons | DM | tDM | Delays due to mechanical problems of the machine. |
Delays caused by operational reasons | DO | tDO | Delays due to operational organization problems, including waiting and performing other tasks not related to pre-skidding and skidding operations. |
Variable | Code and Measurement Unit | Descriptive Statistics | |||||||
---|---|---|---|---|---|---|---|---|---|
Number of Observations | Minimum Value | Maximum Value | Range | Mean Value | Median Value | Sum | Share | ||
Operational variables | |||||||||
Number of pieces | NP | 182 | 1 | 21 | 20 | 4.27 | 3.00 | 777 | 100.00 |
Payload volume | PV (m3) | 182 | 1.70 | 11.29 | 9.59 | 5.05 | 4.69 | 919.16 | 100.00 |
Extraction distance | ED (m) | 182 | 63 | 3081 | 3018 | 1186 | 1037 | 215,917.00 | 100.00 |
Time and fuel consumption variables | |||||||||
Driving to the pre-skidding site | tDET (h) | 182 | 0.077 | 0.432 | 0.385 | 0.201 | 0.186 | 36.640 | 29.23 |
Maneuvering at the pre-skidding site | tMAN (h) | 141 | 0.001 | 0.190 | 0.189 | 0.018 | 0.010 | 2.542 | 2.03 |
Pulling out the cable | tPOC (h) | 182 | 0.002 | 0.110 | 0.108 | 0.030 | 0.026 | 5.508 | 4.39 |
Attachment of the payload | tAPL (h) | 182 | 0.003 | 0.095 | 0.092 | 0.024 | 0.020 | 4.437 | 3.54 |
Pulling in the payload | tPIP (h) | 173 | 0.003 | 0.229 | 0.226 | 0.057 | 0.043 | 9.831 | 7.84 |
Detaching the payload from the cable | tDPC (h) | 141 | 0.002 | 0.080 | 0.078 | 0.023 | 0.018 | 3.182 | 2.54 |
Attaching the payload for extraction | tAPE (h) | 139 | 0.002 | 0.169 | 0.167 | 0.035 | 0.025 | 4.872 | 3.89 |
Driving with the payload to the forest road | tDFR (h) | 182 | 0.093 | 0.565 | 0.472 | 0.269 | 0.251 | 48.928 | 39.03 |
Detaching the payload at the forest road | tDPR (h) | 178 | 0.001 | 0.039 | 0.038 | 0.011 | 0.011 | 1.999 | 1.59 |
Maneuvering and bunching at the forest road | tMBR (h) | 177 | 0.001 | 0.281 | 0.280 | 0.042 | 0.031 | 7.416 | 5.92 |
Skidding work cycle | CT (h) | 182 | 0.237 | 1.527 | 1.290 | 0.689 | 0.648 | 125.354 | 100.00 |
Fuel consumption | FC (L) | 182 | 0.900 | 12.300 | 11.400 | 5.259 | 4.450 | 957.200 | 100.00 |
Variable | Code and Measurement Unit | Descriptive Statistics | |||||||
---|---|---|---|---|---|---|---|---|---|
Number of Observations | Minimum Value | Maximum Value | Range | Mean Value | Median Value | Sum | Share | ||
Operational variables | |||||||||
Number of pieces | NP | 45 | 1 | 12 | 11 | 4.91 | 4 | 221 | 100.00 |
Payload volume | PV (m3) | 45 | 0.98 | 4.92 | 3.94 | 2.80 | 2.94 | 126.05 | 100.00 |
Extraction distance | ED (m) | 45 | 15.5 | 1171.5 | 1156.0 | 590.13 | 645 | 26,556.00 | 100.00 |
Time and fuel consumption variables | |||||||||
Driving to the pre-skidding site | tDET (h) | 45 | 0.019 | 0.199 | 0.180 | 0.108 | 0.130 | 4.83 | 22.57 |
Maneuvering at the pre-skidding site | tMAN (h) | 28 | 0.001 | 0.022 | 0.021 | 0.007 | 0.005 | 0.18 | 0.87 |
Pulling out the cable | tPOC (h) | 45 | 0.003 | 0.127 | 0.124 | 0.037 | 0.034 | 1.65 | 7.71 |
Attachment of the payload | tAPL (h) | 44 | 0.003 | 0.079 | 0.076 | 0.025 | 0.023 | 1.10 | 5.16 |
Pulling in the payload | tPIP (h) | 45 | 0.003 | 0.199 | 0.196 | 0.060 | 0.048 | 2.69 | 12.58 |
Detaching the payload from the cable | tDPC (h) | 45 | 0.000 | 0.051 | 0.051 | 0.017 | 0.014 | 0.76 | 3.55 |
Attaching the payload for extraction | tAPE (h) | 45 | 0.000 | 0.098 | 0.098 | 0.026 | 0.019 | 1.14 | 5.35 |
Driving with the payload to the forest road | tDFR (h) | 45 | 0.035 | 0.362 | 0.327 | 0.170 | 0.198 | 7.66 | 35.77 |
Detaching the payload at the forest road | tDPR (h) | 42 | 0.003 | 0.026 | 0.023 | 0.009 | 0.009 | 0.37 | 1.73 |
Maneuvering and bunching at the forest road | tMBR (h) | 42 | 0.000 | 0.079 | 0.079 | 0.024 | 0.021 | 0.99 | 4.65 |
Skidding work cycle | CT (h) | 45 | 0.112 | 0984 | 0.872 | 0.476 | 0.584 | 21.43 | 100 |
Fuel consumption | FC (L) | 45 | 0.200 | 7.200 | 7.000 | 2.864 | 3.200 | 128.90 | 100 |
Variable | Model | Model Statistics | ||||
---|---|---|---|---|---|---|
Number of Observations | R2 | Model Significance | Independent Variable | Significance of Independent Variable | ||
Skidding work cycle time | ||||||
Skidder | CT (h) = 0.09364 + 0.04509 × PV (m3) + 0.03014 × NP + 0.00020 × ED (m) | 182 | 0.58 | <0.001 | PV | <0.001 |
NP | <0.001 | |||||
ED | <0.001 | |||||
Farm tractor | CT (h) = 0.125355 + 0.00060 × ED (m) | 45 | 0.87 | <0.001 | ED | <0.001 |
Fuel consumption | ||||||
Skidder | FC (L) = 0.80921 + 0.27753 × PV (m3) + 0.00257 × ED (m) | 182 | 0.54 | <0.001 | PV | <0.001 |
ED | <0.001 | |||||
Farm tractor | FC (L) = 0.86869 + 0.00338 × ED (m) | 45 | 0.75 | <0.001 | ED | <0.001 |
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Zurita Vintimilla, M.C.; Borz, S.A. Development of Updated Models to Characterize Skidding Performance in Romania Based on a Nation-Level Dataset. Forests 2025, 16, 1352. https://doi.org/10.3390/f16081352
Zurita Vintimilla MC, Borz SA. Development of Updated Models to Characterize Skidding Performance in Romania Based on a Nation-Level Dataset. Forests. 2025; 16(8):1352. https://doi.org/10.3390/f16081352
Chicago/Turabian StyleZurita Vintimilla, Monica Cecilia, and Stelian Alexandru Borz. 2025. "Development of Updated Models to Characterize Skidding Performance in Romania Based on a Nation-Level Dataset" Forests 16, no. 8: 1352. https://doi.org/10.3390/f16081352
APA StyleZurita Vintimilla, M. C., & Borz, S. A. (2025). Development of Updated Models to Characterize Skidding Performance in Romania Based on a Nation-Level Dataset. Forests, 16(8), 1352. https://doi.org/10.3390/f16081352