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Fig. 1. The procedure to collect trip-level data for modelling of speed and fuel consumption of timber trucks. FMS is the database of a fleet management system, Digiroad the national street and road database, and LogForce the database of a transport management system. The relevant attributes are listed. Truck68t refers to the 68-tonne truck and Truck76t to the 76-tonne truck. n68 and n76 refer to the number of observations of the corresponding trucks.

Table 1. Basic information of the timber trucks. The notation “*4” indicates the second steered axle was located behind the driven tandem.
Combination vehicle Straight truck Full trailer
Id Gross vehicle mass (t) Nominal tracking interval (min) Brand and model Axle configuration Commissioned in Engine displacement (cm3) Output (kW) Tare mass (kg) Loader mass (kg) Brand and model Tare mass (kg)
Truck68t 68 1 Scania
R 560 		6×4 2013 15 607 412 11 750 3500 Feber Intercars
42P0D6 		8250
Truck76t 76 10 Scania
R 580 		8×4*4 2017 16 353 427 13 100 3800 Närko
D4HS11T11 		8500
Table 2. Work phase division of timber trucking for the estimation of truck speed and fuel consumption (adapted from Nurminen and Heinonen 2007).
Work phase Definition
Driving without load Begins when the truck leaves the mill storage area after unloading and ends when the truck stops at a roadside storage to receive a new load.
Loading Begins when the truck stops at a roadside storage and ends when the truck leaves for the mill or for travel to the next roadside storage. In addition to actual loading, includes auxiliary activities like preparing the crane, driving between piles, handling the trailer and bunks, and binding the load.
Driving between roadside storages Begins when the truck leaves one roadside storage and ends when the truck stops at the next.
Driving with load Begins when the truck leaves the last roadside storage and ends when the truck stops at a mill yard.
Unloading Begins when the truck arrives at a mill yard and ends when the truck leaves without a load. In addition to actual unloading, includes queueing and waiting, and auxiliary activities like preparations, scaling, and driving between unloading locations.
Other driving Begins when the truck turns off the route and ends when the truck is back on the route. The minimum time for other driving was set at 2 h.
Break, max 15 min Begins when the truck stops for a break of at most 15 minutes and ends when the truck continues driving.
Break, over 15 min Begins when the truck stops for a break of more than 15 minutes and ends when the truck continues driving.
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Fig. 2. An example of the interpreted work phases of a trip (above) and the corresponding fuel consumption as a function of driving distance of a timber truck (below).

Table 3. Road classes in Digiroad (Finnish Transport Infrastructure Agency 2018) and their reclassification for regression analysis of driving speed and fuel consumption.
Road class Reclassification
Class I main road Main road
Class II main road Main road
Regional road Main road
Connecting road Collector road
Class I private road Collector road
Unknown road class Collector road
Class II private road Forest road
Vehicle track Forest road
N/A Forest road
Table 4. Pavement classes in Digiroad (Finnish Transport Infrastructure Agency 2018) and their reclassification for regression analysis of driving speed and fuel consumption.
Pavement class Reclassification
Hard asphalt concrete Asphalt
Soft asphalt concrete Asphalt
Gravel surface Gravel
Gravel wear layer Gravel
Paved, type unknown Gravel
No pavement No pavement
Table 5. Summary of the examined trips for the 68-tonne and 76-tonne trucks.
Truck68t Truck76t
Number of trips 80 24
Average trip distance (km) 203 160
Minimum trip distance (km) 23 60
Maximum trip distance (km) 385 335
Average load (t) 49.5 49.3
Minimum load (t) 35 36.1
Maximum load (t) 54.1 57.7
Number of crossings 1888 490
Total time consumption (h) 578 135
Total fuel consumption (l) 9279 2546
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Fig. 3. Distribution of driving distance, driving time, and fuel consumption for the 68-tonne and 76-tonne timber trucks.

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Fig. 4. Distribution of trip-level average truck speed of driving work phases for the 68-tonne and 76-tonne timber trucks.

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Fig. 5. Distribution of trip-level fuel consumption of driving work phases for the 68-tonne and 76-tonne timber trucks.

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Fig. 6. Distribution of trip-level fuel consumption of non-driving work phases for the 68-tonne and 76-tonne timber trucks.

Table 6. Total distances (km) in functional and pavement classes for the 68-tonne and 76-tonne trucks.
   Hard asphalt concrete Soft asphalt concrete Gravel surface Gravel wear layer Paved, type unknown Unpaved Total
Truck68t Class I main road 9465 0 0 0 11 0 9476
Class II main road 2567 857 0 0 0 2 3426
Regional road 258 494 0 0 50 0 802
Connecting road 108 723 8 568 146 2 1555
Class I private road 1 0 0 0 29 0 30
Class II private road 0 0 0 3 72 745 820
Vehicle track 0 0 0 0 0 12 12
No data 0 0 0 0 2 10 12
Total 12 399 2074 8 571 310 771 16 133
Truck76t Class I main road 1368 0 0 0 0 0 1368
Class II main road 1493 0 0 0 0 0 1493
Regional road 337 89 0 0 0 0 426
Connecting road 25 182 0 59 82 0 348
Class I private road 0 0 0 0 17 7 24
Class II private road 0 0 0 0 0 105 105
Vehicle track 0 0 0 0 0 19 19
No data 0 0 0 0 0 7 7
Total 3223 271 0 59 99 138 3790
Table 7. Average speed (km h–1) in functional and pavement classes for the 68-tonne and 76-tonne trucks. For comparison, the values in ESRI Finland’s (2019) data set are given. The darkness of cell shading indicates speed.
   Hard asphalt concrete Soft asphalt concrete Gravel surface Gravel wear layer Paved, type unknown Unpaved Average ESRI Finland
Truck68t Class I main road 76       40   76 80
Class II main road 76 71 75 76
Regional road 51 70 28 58 65
Connecting road 35 52 48 45 33 40 45 48
Class I private road 10 10 40
Class II private road 60 32 20 21 30
Vehicle track 9 9 20
No data 4 4  
Average 74 63 48 45 26 19 61  
Truck76t Class I main road 69           69 80
Class II main road 70 70 76
Regional road 60 46 56 65
Connecting road 38 45 40 28 38 48
Class I private road 15 12 40
Class II private road 17 17 30
Vehicle track 10 10 20
No data 13 13  
Average 68 46   40 24 14 56  
Table 8. Average fuel consumption (l(100 km)–1) in functional and pavement classes for the 68-tonne and 76-tonne trucks. The darkness of cell shading indicates fuel consumption.
   Hard asphalt concrete Soft asphalt concrete Gravel surface Gravel wear layer Paved, type unknown Unpaved Average
Truck68t Class I main road 47       82   47
Class II main road 48 48 48
Regional road 49 47 54 48
Connecting road 58 54 88 63 59 50 59
Class I private road 62 62
Class II private road 67 67 82 81
Vehicle track 133 133
No data 90 81
Average 48 50 88 63 62 83 50
Truck76t Class I main road 51           51
Class II main road 53 53
Regional road 58 52 57
Connecting road 60 59 58 59 59
Class I private road 82 61
Class II private road 83 83
Vehicle track 111 111
No data 86 86
Average 52 57   58 64 84 54
Table 9. Total driven kilometres by driver for the 68-tonne and 76-tonne timber trucks.
Truck Driver Total distance (km)
Truck68t 1 7430
Truck68t 2 6829
Truck68t 3 1362
Truck68t 4 490
Truck68t 5 2
Truck76t 6 1900
Truck76t 7 1371
Truck76t 8 243
Truck76t 9 99
Truck76t 10 90
Truck76t 11 46
Truck76t 12 25
Truck76t 13 9
Table 10. Statistics of the trip-level speed and fuel consumption models for a 68-tonne timber truck. The unit of RMSE of the speed models is km h–1 and of the fuel consumption models l(100 km)–1.
Model n RMSE R2adj F-test
Speed when driving without load 79 4.3 0.84 F(5,73) = 80.47, p < 0.001
Speed when driving with load 80 3.7 0.77 F(6,73) = 43.96, p < 0.001
Fuel consumption when driving without load 79 2.6 0.52 F(5,73) = 18.21, p < 0.001
Fuel consumption when driving with load 80 4.4 0.47 F(6,73) = 12.71, p < 0.001
Table 11. Parameter estimates and test statistics of the 68-tonne timber truck speed models for driving without a load. ForestRoad = proportion of forest roads when driving without a load; Gravel = proportion of poor asphalt and gravel roads when driving without a load; Crossings = number of road crossings when driving without a load ((100 km)–1); DecFeb = 1 if the transport date is within range [December, February], otherwise 0; MarMay = 1 if the transport date is within range [March, May], otherwise 0.
Term Estimate Std. error t-test
Intercept 77.3 1.1 t(73) = 71.25, p < 0.001
ForestRoad –44.6 5.3 t(73) = –8.44, p < 0.001
Gravel –31.4 7.4 t(73) = –4.22, p < 0.001
Crossings –0.7 0.1 t(73) = –12.51, p < 0.001
DecFeb –3.1 1.2 t(73) = –2.56, p = 0.013
MarMay –3.4 1.2 t(73) = –2.81, p = 0.006
Table 12. Parameter estimates and test statistics of the 68-tonne timber truck speed models for driving with a load. ForestRoad = proportion of forest roads when driving with a load; Asphalt = proportion of hard and soft asphalt concrete when driving with a load; Crossings = number of road crossings when driving with a load ((100 km)–1); SepNov = 1 if the transport date is within range [September, November], otherwise 0; DecFeb = 1 if the transport date is within range [December, February], otherwise 0; MarMay = 1 if the transport date is within range [March, May], otherwise 0.
Term Estimate Std. error t-test
Intercept 36.0 6.3 t(73) = 5.74, p < 0.001
ForestRoad –22.6 13.4 t(73) = –1.69, p = 0.095
Asphalt 42.1 6.4 t(73) = 6.57, p < 0.001
Crossings –0.8 0.1 t(73) = –8.65, p < 0.001
SepNov –3.2 1.2 t(73) = –2.67, p = 0.009
DecFeb –2.7 1.2 t(73) = –2.26, p = 0.027
MarMay –2.8 1.2 t(73) = –2.33, p = 0.023
Table 13. Parameter estimates and test statistics of the 68-tonne timber truck fuel consumption models for driving without a load. ForestRoad = proportion of forest roads when driving without load; Loader = proportion of distance traveled with a loader when driving without load; Crossings = number of road crossings when driving without load ((100 km)–1); SepNov = 1 if the transport date is within range [September, November], otherwise 0; DecFeb = 1 if the transport date is within range [December, February], otherwise 0.
Term Estimate Std. error t-test
Intercept 38.0 0.9 t(73) = 40.60, p < 0.001
ForestRoad 9.0 3.2 t(73) = 2.83, p = 0.006
Loader 2.5 1.0 t(73) = 2.38, p = 0.002
Crossings 0.1 0.0 t(73) = 4.17, p < 0.001
SepNov –3.1 0.8 t(73) = –4.15, p < 0.001
DecFeb 2.3 0.8 t(73) = 3.074, p = 0.003
Table 14. Parameter estimates and test statistics of the 68-tonne timber truck fuel consumption models for driving with a load. Asphalt = proportion of hard and soft asphalt concrete when driving with a load; Gravel = proportion of poor asphalt and gravel roads when driving with a load; Crossings = number of road crossings when driving with a load ((100 km)–1); Mass = Total mass of the truck (t); DecFeb = 1 if the transport date is within range [December, February], otherwise 0; MarMay = 1 if the transport date is within range [March, May], otherwise 0.
Term Estimate Std. error t-test
Intercept 86.7 17.4 t(73) = 4.97, p < 0.001
Asphalt –54.1 12.7 t(73) = –4.25, p < 0.001
Gravel –44.1 15.8 t(73) = –2.80, p = 0.007
Crossings 0.4 0.1 t(73) = 3.36, p = 0.001
Mass1.1 0.2 0.1 t(73) = 1.75, p = 0.084
DecFeb 2.9 1.2 t(73) = 2.31, p = 0.023
MarMay 2.7 1.2 t(73) = 2.26, p < 0.027