The Analysis of the Cause-Effect Relation between Tractor Overturns and Traumatic Lesions Suffered by Drivers and Passengers: A Crucial Step in the Reconstruction of Accident Dynamics and the Improvement of Prevention
2. Tractor Overturn Risk Factors
- Human behavioral factors in which tractor drivers:
- ignore or fail to observe correct standards of conduct when behind the wheel
- corner abruptly and at speed
- are working alone for long periods, in adverse environmental and weather conditions, in isolated, rural areas (82% on farms and only 18% on public roads, as reported by the US Centers for Disease Control and Prevention) where it may be extremely difficult to get rapid access to emergency services and medical aid; such work may also be performed at night without an efficient lighting system [9,12].
- may have been drinking or taken drugs, thus affecting reaction times
- may be elderly and have cardiovascular or neurological issues which dangerously affect reaction times and the ability to recover from trauma
- Factors involving ground and weather conditions:
- the ground can become slippery with the tractor operating in conditions where there is a dangerous coefficient of traction which leads to side, rear or front overturns (The coefficient of traction between two surfaces, e.g., rubber tyre and ground surface, is expressed by the following equation: Af = Ca × Cf, where Af is the frictional force which resists the relative motion between two surfaces (tyre and ground), Ca is the coefficient of traction between those two surfaces, and Cf is the compression force involving two opposing surfaces (i.e., the weight bearing upon the wheel)) .
- verges, escarpments and the banks of waterways may become waterlogged and give way.
- Factors involving the technical or functional characteristics of tractors: farm tractors have a high center of gravity and/or a narrow axle track; they may be rather old and not equipped with adequate or upgraded safety systems; they may also be poorly maintained and have the wrong tyre pressures.
- Factors due to the behavior of machinery and equipment towed by a tractor and coupled to the PTO:
- excessive loads towed by a tractor.
- excessive loads may be towed by a tractor and coupled to a functioning PTO; in both cases the operator may fail to consider the fact that the PTO coupling and the heavy load will cause the vehicle to behave differently when, for example, cornering or traversing a slope.
3. Genesis of Traumatic Lesions Caused by Tractor Overturn
- E = σ/ε where:
- E is Young’s Modulus expressed in Newtons/surface area in m2 of the body involved
- σ = force/surface, is the ratio between the applied force and the surface area of the body involved, orthogonally to the force applied
- ε = Δl/l is the ratio between the length of the body after and before the load is applied.
- Deformation caused by bending processes is expressed by the following equation:
- H = σ/ε where:
- H is the Flexural Modulus expressed in Newtons/ surface area in m2 of the body involved
- σ = force/surface is the ratio between the applied force and the surface area of the body involved
- ε = Δl is the amount of flexion.
- The deformation produced by torsion is expressed by the following equation:
- K =σ/θ where:
- K is the Torsion Modulus expressed in Newtons/ surface area in m2 of the body involved
- σ = force momentum/surface is the ratio between the applied force and the surface area of the body involved
- θ = Δ° is the torsion angle.
4. Traumatic Injury Patterns Due to Tractor Overturn
- brush burn abrasions
- tearing and bruising
- sharp injuries
- cuts and sharp injuries
- tissue loss.
- flat surfaces [i.e., side walls of the cabin, mudguards, engine covers, as well as the ground (farmland, tracks or roads)].
- uneven surface which may be rounded, pointed, sharp or irregular (i.e., the ROPS, the steering wheel, uncovered parts of the engine, type tread, rocks, branches or tree-trunk slying on the ground) .
- thrown to the ground and crushed by the vehicle with lethal injuries to the chest, head or limbs
- thrown to the ground and suffering serious or fatal injuries due to the fall and collision with rocks, tree trunks, branches or the ground/road
- thrown to the ground and crushed more than once by the machine in cases of multiple rollovers and then found fatally crushed at some distance from the machine
- thrown to the ground and crushed more than once by the tractor in the event of multiple rollovers, with the victim found crushed under the vehicle
- thrown to the ground and run over by the still moving tractor
- thrown into water (streams, irrigation channels, ponds, lakes, etc.), crushed and drowned
- entangled in and/or strangled by the moving tractor parts resulting in lethal mutilation (i.e., from the PTO or Power Take-Off)
- injured by foreign objects, such as rocks, branches or tree trunks penetrating the cabin safety zone during single or multiple rollovers
5. Pathophysiology of Traumas Caused by Tractor Overturn
6. Morphology, Anatomical Location and Cause-Effect Relation of Traumatic Lesions Due to Tractor Overturn
- head and chest (16.3%)
- chest and abdomen (12.8%)
- head, chest and abdomen (9.3%)
- head, chest, abdomen and extremities (5.8%)
- chest, abdomen and extremities (2.3%)
- head, chest and extremities (1.2%)
- head and abdomen (1.2%)
- head, abdomen and extremities (1.2%)
- head and extremities (1.2%)
7. Medicolegal and Technical Implications
- to interact with experts in the field of agricultural engineering to evaluate and discuss any technical and mechanical issues which may help to understand the dynamics of the event (single sideways rollover within 90°, single/multiple sideways rollover more than 90°, single or multiple rear or front rollovers).
- to evaluate the death scene, the structural, mechanical and technical features of the vehicle, its direction of travel before and during the accident, the gradient of the slope and the morphology of the ground, weather and light conditions at the time of the accident and the type of work being performed at the time and its setting, i.e., whether it is (a) agricultural or zootechnical work, in fields or wooded areas, involving pruning, or sawing tree-trunks and branches; (b) normal field work, cultivation of a vegetable garden or arable land; (c) maintenance work such as hedge and grass cutting on farms or in parks and gardens; or (d) processes such as harvesting, haymaking, pruning or irrigation;
- to verify whether certified ROPS were fitted, whether a helmet and seat belt was fitted and in use;
- to analyze whether the morphology and characteristics of the various lesions, both superficial and deep, and in any anatomical area of the corpse, match any specific parts of the machine, ground or objects external to the cabin ;
- to search for all specific signs of crush asphyxia (distinguishing the distribution of post-mortem lividity from the position of the ecchymotic mask or any ecchymosis in other areas of the body) and all thoracic and extrathoracic traumatic lesions caused by the accident;
- to reconstruct the medical history of the deceased and his/her psycho-physical condition when of the accident;
- to analyze toxicological data for signs of alcohol or drug use;
- to exclude any causes of death other than the lesions produced during the rollover and evaluate the vitality of wounds present at the moment of death, in order to be sure that it was not a homicide made to look like an accident, nor was it a death from other causes not covered by insurance, that was made to look like a fatality caused by tractor rollover;
- to exclude any natural cause of death (i.e., stroke, cardiovascular acute pathologies) responsible for the loss of control of the vehicle and its rollover;
- ascertain how isolated the scene of the accident was, and investigate the involvement of the rescue services (when they were alerted, the distance covered, and the time of arrival at the scene);
- ascertain if the victim died when of the accident, on the way to hospital or after admission to hospital .
8. Concluding Remarks
- retrospective analysis and statistical description phases with analysis of (a) the level of preparedness and perception among farm tractor drivers of the risk of accidents, (b) the causal dynamics of serious and fatal accidents, including the analysis of fatal or disabling injuries and further work on the demographic characteristics and age of the drivers, on the type of work performed and the topography of the scene of the accident 
- experimental simulation phases, with the definition of test scenarios and their relative models (prototype-vehicles, dummies, etc.)
- final phases of proposals and solutions with the design of innovative tractors, equipment/devices and new models of driver behaviour .
- even when inside a ROPS-equipped cabin and when wearing seat belt and helmet, the driver can still suffer serious, and sometimes fatal, injury because of a single or multiple rollover beyond 90°, when foreign objects (rocks, branches, tree-trunks, etc.) penetrate the driver’s safety zone or, in the event of a multiple rollover, if the ROPS collapses [11,25];
- during rapid acceleration and deceleration when the vehicle is rolling, even when the tractor is equipped with ROPS and the driver is wearing helmet and seat belt, serious trauma can occur, resulting in injuries to the head, chest, abdomen and limbs due to the body hitting the front, rear or side of the cabin interior or foreign objects which intrude into the Deflection Limiting Volume [11,12,25].
- improve experimental observations regarding the dynamics of tractor rollovers and the genesis of the different injuries caused by such accidents (the mechanical characteristics of the vehicle, the kind of accident and its location, the typology and location of lesions, the relative final positions of the victim and the vehicle) ;
- foster close cooperation between coroners and engineers;
- strive to develop new preventive devices, equipment and procedures (wrap-around seats which reduce lateral movement, compulsory fitting of audio alarms in the cabin, cushioning systems to offer greater protection to front and rear for the head, chest and pelvis, inclinometers which electronically control engine shutdown and braking systems);
- ensure that only properly trained people can drive tractors and other agricultural equipment;
- ensure that people with psychophysical impairments are not allowed to drive tractors and other agricultural equipment; this may include elderly, infirm or retired farmers or members of farming families; this issue is of particular importance nowadays when many countries in Europe are encouraging or forcing people to remain active and keep working longer, with the result that there tend now to be more people driving these vehicles in advanced age, and this may, in turn, increase the number of fatalities due to tractor rollovers [1,8,12,42,43,44].
Conflicts of Interest
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Moreschi, C.; Da Broi, U.; Cividino, S.R.S.; Gubiani, R.; Pergher, G.; Vello, M.; Rinaldi, F. The Analysis of the Cause-Effect Relation between Tractor Overturns and Traumatic Lesions Suffered by Drivers and Passengers: A Crucial Step in the Reconstruction of Accident Dynamics and the Improvement of Prevention. Agriculture 2017, 7, 97. https://doi.org/10.3390/agriculture7120097
Moreschi C, Da Broi U, Cividino SRS, Gubiani R, Pergher G, Vello M, Rinaldi F. The Analysis of the Cause-Effect Relation between Tractor Overturns and Traumatic Lesions Suffered by Drivers and Passengers: A Crucial Step in the Reconstruction of Accident Dynamics and the Improvement of Prevention. Agriculture. 2017; 7(12):97. https://doi.org/10.3390/agriculture7120097Chicago/Turabian Style
Moreschi, Carlo, Ugo Da Broi, Sirio Rossano Secondo Cividino, Rino Gubiani, Gianfranco Pergher, Michela Vello, and Fabiano Rinaldi. 2017. "The Analysis of the Cause-Effect Relation between Tractor Overturns and Traumatic Lesions Suffered by Drivers and Passengers: A Crucial Step in the Reconstruction of Accident Dynamics and the Improvement of Prevention" Agriculture 7, no. 12: 97. https://doi.org/10.3390/agriculture7120097