Forestry operations and OSH issues: from the past to the present
Kari Ojanen, Finnish Institute of Occupational Health, Finland
- 1 Introduction
- 2 Research on safety of forestry machine
- 3 Forestry operations
- 4 Laws and regulations
- 5 Safety and health in logging operations
- 6 Preventive measures
- 7 Technical solutions
- 8 Conclusions
- 9 References
- 10 Links for further reading
Forestry transportation refers to the transportation of timber or other forestry biomass from the logging site to the road for further treatment, or transportation to the pulp or saw mill, or to be burned at the power plant. When the tree has been felled, it is handled (by the harvester), the technical term is "limbed". There are two common ways to handle the limbed trunk before the forestry transport. Typically, in Nordic countries, the cut-to-length method is used, whereas elsewhere in Europe and in other continents the full-tree method is more common. However, the use of the cut-to-length method is increasing in many countries. The methods and equipment will be described here, as well as the variety of the transported materials. In addition, safety and health of forestry tractor and harvester operators will be addressed. Commuting of forestry workers to or from their working sites is not discussed.
Research on safety of forestry machine
Most of the information concerning safety and health issues on forestry machine operations emerges in studies done in New Zealand, Northern America and the Nordic countries. There is an extensive Swedish review  covering the period from the beginning of the forestry work mechanisation to the year 2005. Since the appearance of this review there have been no significant changes in forestry work methods. Only the utilisation of forestry biomass for energy production has increased.
In North America, New Zealand and the Nordic countries there is high awareness about safety concerns. It is a common experience that the prevalence of accidents decreases with increasing mechanisation and the declining proportion of manual and motor-manual tasks. However, the prevalence of accidents during mechanised work in the forest is at the same magnitude as throughout the industry at large. When it comes to safe work, much attention should be devoted to strategies that can be implemented through organisational changes. The other main area is technical solutions.
Musculoskeletal disorders, psychosomatic complaints and hearing loss are the most common health complaints. In recent years, there has been a decline in the occurrence of low back pain, but at the same time neck and upper extremity disorders have increased. These are probably due to the increasing mechanisation of forestry work. During the last few decades there has also been a tendency for more accidents during harvesting than in the forestry transport phase. The most dangerous activities are repair and maintenance work, and climbing into and out of the cabin .
The EU-28 has approximately 180 million hectares of forests and other wooded land, corresponding to 42.4 % of its land area.  The enlargement of the EU in May 2004 to 25 Member States increased the amount of forested and wooded land in the European Union area by 20%. Forest coverage ranges from 1.1% in Malta to 72% in Finland, with the largest forested areas located in Sweden, Finland, Spain and France The amount of forested land continues to expand, and Europe has a great diversity of forest types. The three main forest zones in Europe are:
- The boreal coniferous zone forests with firs, spruces and pines;
- The central European forests of birches, oaks, maples and beeches;
- The Mediterranean forests of eucalyptus, cork-oak, stone and maritime pine, chestnut and holm oak.
Fully mechanized harvesting by harvester and forwarder (cut-to-length method) is commonly used in coniferous stands . In the Nordic countries, more than 95% of timber (logs and pulpwood) is felled and processed by harvesters and transported (almost 100%) to the roadside by forwarders (Figure 1).
Source: Drawings copyright of K. Ojanen (FIOH), published with special permission in this article.
Mixed stands or stands with broad leaved trees as well as big formatted coniferous trees are processed motormanually and transported by simple or advanced machine work with skidders. The combination of motormanual processing and the transport operation by simple machines is used in the eastern regions of Central Europe. In wet and inaccessible forest areas or hilly forests the use of agricultural tractors is rather limited .
Europe is one of the largest producers of roundwood in the world. In 2010, more than 578 million cubic metres of roundwood were produced. The four largest roundwood producers in Europe are:
- Sweden (about 70 million m3 wood and about 2,000 harvesters and 2,200 forwarders);
- Finland (about 50 million m3 wood and about 1,300 harvesters and 1,600 forwarders);
- France (almost 50 million m3 wood and about 800 harvesters, 1,200 forwarders and 1,400 skidders);
- Germany (about 50 million m3 wood and about 1,000 harvesters and 3,000 forwarders) , , , .
Trees are felled, delimbed, cut and bucked to various assortments directly in the stump area by a harvester and transported to the roadside by forwarders prior to truck transport to the saw mills or pulp factories. Forwarders are especially designed for moving in the forest and for carrying heavy loads. The weight of a typical forwarder can range from 10 tons to over 20 tons and it can carry from 10 tons to over 20 tons. It is usually equipped with 4 to 8 very wide wheels, in wintertime with tyre chains, and in soft terrains with a forestry tractor tread, especially on the front tyres of the harvester (see Figure 1).
Using the full-tree method, trunks are (pre)limbed mostly by loggers and hauled to the landing/roadside by skidders or cable track to allow truck transport to saw or pulp mills. The skidder differs from the load carrying forwarder so that a skidder drags the timber along the ground, as shown in Figure 1. The load is then dragged to the landing so that the other ends of the stems are trailing the ground. Usually, skidders are four-wheelers and wheel chains can be used on slippery ground.
Transportation of forestry biomass for energy production
In the European Union and especially in the Nordic countries, Austria, France and Germany wood is being used more and more as an energy source. Typically, wood from forestry and from wood industry can be used in the form of firewood, wood chips, bark, shavings, briquettes, pellets, and demolition wood. The EU is currently the world’s largest market for wood pellets.  According to the annual biofuels report for 2013, the European Biomass Association expects that Europe will reach a consumption of 50 million tons per year by 2020 compared with 8 million tons per year in 2009.  The traditional forestry bioenergy raw materials are logging residues and small size stems. The utilization of stumps and roots of the harvested timber is rather new among the forestry bioenergy raw materials.
There are three possible ways to harvest wood for energy from logging residues:
- Chipping on the area with a mobile chipper
- Forwarding the residues to the roadside and chip at the landing area
- Bundling the residues, forwarding to the roadside.
Wood chips or cutter chips are mechanically chopped wood usually up to a length of 15 cm.
Most of the logging residues and small size stems are transported loosely to the landing by a forwarder. They can also be baled by a special forestry machine intended for logging residue baling .
Laws and regulations
At the EU level, Council Directive 89/391/EEC  establishes the minimum occupational safety and health standards, such as methods to improve safety and health at workplaces, general duties of employers and workers, the hierarchy of control measures, and requires risk assessments to be carried out. There are no specific EU laws or official regulations concerning forestry transportation of wood, although there are several directives providing guidance on risk assessment, personal protective equipment, safe use of work equipment, preventing exposure to chemical, biological and physical agents, etc. which all apply to work at forest as well.
European occupational safety and health legislation has been transposed to national legislation in each member state, though as mentioned previously, few countries have particular forestry transportation legislation. For example, the only legislation which touches on the forestry transportation at the national level in Finland is the State regulation concerning safety in wood harvesting work . This states that before starting the wood harvesting processes occupational risks factors connected with steep slopes, soft terrains, water crossings, power lines, passages and other risk factors must be considered. Concerning the logging site, there must be a preventive scheme and a map describing the work site, its borders, topography and possible hazardous places, as well as the main transport directions. This relates to general European legislation and standards defining the need of having completed a risk assessment– planning and organising is key to preventing accidents.
There are recommendations and instructions at the national level at least in Finland and Sweden concerning the trails to be used by forwarders/forestry tractors on the logging site. Those instructions mostly deal with the distance from one trail to another and the width of the trails. The instructions may also deal with damage to trees left standing (e.g. the damage caused by forwarder contacting the trees and damaging the bark) and the roots (e.g. damage done while driving over roots on or near the ground surface) of the trees. The German statutory accident insurance for agriculture provides among others guidance and accident prevention regulations for cargo securing in forestry  and forestry work in general.  If the forwarder/forestry tractor is driven on the public road, general legislations and regulations concerning occupational safety and health in transportations are applicable.
The ILO has published an ILO code of practice, Safety and health in forestry work . It deals in detail with the whole logging process and defines the general principles, legal framework and general duties concerning different actors like civil authorities, employers, managers and supervisors, workers and manufactures and suppliers of equipment and substances. It also addresses loading and road transportation of the harvested timber.
Safety and health in logging operations
An accident will occur as a consequence of an unforeseen and unwanted event of a random character. Accidents in forestry transportation, as with any other work sector, may have various consequences ranging from fatal accidents to accidents leading to injury and lost working days or even minor events leading only to material loss and a brief interruption in the work. A special event related to accidents is the near-accident where the situation might have led to an accident, but where luck or special alertness led to the avoidance of an accident . The following glance at the history of the development of logging operations techniques describes how the profile of risks and accidents has changed with the introduction of different work procedures in harvesting/logging operations.
Hand saws and axes
The logging work force increased rapidly after the Second World War in the Nordic countries, especially in Finland, where the main reason was the indemnity to be paid after the war. At the European level, it was the growing need for building material and, in the Nordic countries, the rapidly growing pulp and paper industry. In the 1950’s, there could well have been over 150,000 loggers working in the forestry sector in Finland compared to the fewer than 15,000 nowadays . At first, the work was done by axe and hand saw using manpower with forestry transportation done by horses.
In the 1960s the first chain saws were introduced into forestry harvesting. At that time, logging work was one of the most dangerous occupations. Quite often, the logging areas looked different from today: old forests with dense tree growth. Therefore, while felling a tree, it could get stuck tight against a standing tree (hung-up). Handling hung-up trees down is one of the most risky logging stages. Nowadays, hung-up trees are not a problem when using harvesters for felling. However, accidents can still happen in motor-manual logging. The safest way to take down the hang-up trees is to mark the risky area around it and pull it down when the forwarder comes to the logging site. Figure 2 illustrates how to take a hung-up tree down by using manpower.
The most common accidents in those 'axe-saw years' were striking the leg with an axe and different kinds of musculoskeletal disorders. During the 'chain saw decades' most accidents were injuries connected to the chain saw. For example, when chain saws were introduced, there was no personal protective equipment use. Gradually, from the end of 1970’s onwards the first loggers’ personal protectors ( helmet, ear and eye protectors) were introduced. In addition, legislation about worker protection started to take into account personal protection in general. Nowadays, most accidents happen during leisure time or/and typically by non-professional loggers, for example farmers.
Mechanisation of logging positively influenced the risk level of logging workFrom the end of 1970’s onwards the risk levels decreased from being the most accident prone occupation down to average risk levels in the Nordic countries (in 2011, 11 accidents with over three days absence per million working hours when the average value of all occupations was 13.2 accidents per million working hours). Fatality rates in Sweden and Finland are 0.03 fatalities/10 million m3 harvested wood on average, (professional forest workers, period years 2000-2004). In Germany, the corresponding rates are at 0.16, in Austria 0.83 and in Switzerland 1.00 . However, forest work is still considered one of the most dangerous occupations in the world. In particular dangerous are felling and cross-cutting, no no exact numbers on accidents incurred by forestry tractor (forwarder) operators are available, but the majority of the accidents occur while repairing and servicing forestry tractors at work sites. In the past decades, machinery has become more and more reliable, thus the need for repair and service work has decreased and in conjunction, the number of work accidents. The second potentially hazardous task is climbing into and getting out of the cabin of the forwarder or harvester. Too often, the operator jumps out of the cabin to the rough terrain or/and slippery (e.g. snow, branch strewn) ground.
About 20 occupational diseases per 10,000 workers are notified annually in Sweden and Finland. The most common diseases are hearing loss, musculoskeletal diseases and skin diseases (due to hydraulic oils, fuel, etc.).
In mountainous regions (e.g. Austria, Switzerland) different wood transport methods are required: different cable logging systems have been developed and even helicopters are used to transport wood out of the forest.
Wood transport is the link between forest harvesting and the saw mills or pulp factories. Wood transport includes loading, transporting and unloading of wood logs. Even if fully mechanised, loading and unloading remain hazardous. It may be done on landings or at roadside. Landing area brings together ground workers, machines and vehicles. Here different operations such as delimbing, debarking, storing, chipping, loading and unloading are performed and should be carefully managed 
Wood transport itself includes a drive on an unsealed forest road, then a journey on a narrow local road before getting on the national roads for most of the journey. Transport of wood on public roads underlies the road safety legislations. Special attention should be given to cargo securing . It is very important that vehicles are loaded safely and load is safe and secure for transport to avoid injury to the operator, the public and other road users. Longitudinal loading of roundwood may result in increased risk of moving forwards and possibly striking the vehicle cab and injuring drivers in case of severe breaking.
The load restraint system must be sufficient to stop the total weight of the load moving forwards under severe braking, The Code of practice for road haulage of round timberload requires that 'all bays of timber should be secured with at least one strap and the first bay should have two straps where there is no headboard'.  The European Best Practice Guidelines on Cargo Securing for Road Transport provide information and guideline on timber load securing.
The growing use of forestry based bioenergy may lead to new, yet unknown safety and health risks.  Forestry bio(energy)mass e.g., stumps, small size stems and logging residues (limbs and tops) are stored at the road sides to allow them to dry. The storage period is about one year. If the conditions are poor (e.g. rainy summer) mould and fungi can start growing and may put workers at risk of being exposed.
Different types of chippers have also been introduced. Workers working with chipping machines are exposed to high noise levels of hearing loss?, whole body vibrations as well as had-arm vibrations.  The health effects of these exposures are known but the amount of the exposure during the forestry bioenergy raw material production is not known. Research on potential exposure and risks is currently ongoing in Finland and Sweden (e.g. at the Finnish Institute of Occupational Health, the Finnish Forest Research Institute and the Dalarna University in Sweden).
Working conditions in mechanised forestry machine work are composed of two main areas: the organisational arrangements  and technical solutions . The aim of all safety and ergonomic measures is to:
- prevent ill health and accidents
- support well-being
- achieve a satisfactory working environment
- reduce costs
- increase profitability.
Risk assessment and organisational arrangements
The organisational steps to achieve safe and healthy working conditions is to develop workplace specific safety and health policies and routines. A policy should be concrete, be easy to understand, and be supported by key indicators. These policies must be clearly stated. Routines should clearly indicate who is responsible for implementing the safety policy and practical actions, and when, how and by whom the work and the work environment management is to be conducted. This step is important especially since wood harvesting work site is often a shared work place were contractors and subcontractors are working together, and smooth communication is needed to.guarantee a safe working environment.
The first step of risk assessment is to identify the hazards and to identify workers who may be exposed to the hazards. For example during logging operations or loading and unloading of timber (available machines and tools, number of workers, workers qualification etc.).
The second step is to evaluate assess the potential the risks and to prioritise them in order of importance.. Main categories to classify the urgency of preventive measures according to the probability and severity are:
- Immediate actions necessary
- Sufficient correcting action within some time
- No risk is observed.
Potential hazards in machine work can be e.g. long operating hours in fixed positions, repetitive work, sustained high levels of attention, whole body vibration, jolts and bumping and inclined seating in poor seats. In addition, several mechanical properties of the machines in use must be evaluated (see following chapter on “Technical solutions”) . Aggravating circumstances can be working alone, working in the dark, shift work, unclear instructions, poor equipment, and working under production pressure.
The third step of risk assessment is to decide on preventive actions. Appropriate measures to eliminate or control the risks have to be identified. Examples of preventive measures are micro pauses and rest breaks, evaluating and modifying working postures, training in working techniques, and reducing machine (operating) hours, and aiming for job enlargement.
The fourth step is to take action by putting in place the preventive and protective measures through a prioritisation plan. Furthermore, documentation of the activities, the goal and key indicators, scheduling, the person in charge and other involved persons, sanctions and costing and financing is needed.
Finally, according to the principle of continuous improvement, follow up is essential. For example, through an assessment of work organisation and job satisfaction, by measuring health and safety indicators like accidents, diseases or other health problems, assessment of work shift rosters. In addition, costs for ill health and preventive measures can be estimated and, making strengths and weaknesses in the work conditions visible.
Internationally much work has been carried out to stimulate forest companies to organise effective safety at work. For example, the International Labour Office (ILO) provides information material concerning OSH in forestry  , .
The other main area in Forestry transportation to achieve proper working conditions is via technical solutions. For forestry machines general machine safety principles must be fulfilled. In Europe, there are also some design instructions for forestry machines, for example ”the Ergonomic Checklist for Forest Machines” . According to this checklist many accidents among forest machine operators occur for example when they enter or leave the machine. They may jump down or miss the footing, fall or slip down. A safe cab access should be designed according to the guideline among others taking into account:
- Distances and dimensions of the footsteps: ground to first step ≤ 40 cm, step depth: ≥24 cm, step width ≥ 40 cm.
- Steps with a good grip and a minimum risk of slipping
- Handrail: ground to handrail 85-130 cm, step to handrail 85 – 100 cm.
Traditionally, the forest has been considered a rather dangerous workplace. It differs substantially from the indoor workplace of an industrial worker. Climate, terrain conditions, and a great variation in the forest stands are challenges to the forest worker. In an industrial building, the climate can be controlled, floors are fairly even and of a non-slippery material, and machines and tools can easily be adapted to the workers specific needs.
The introduction of machines into the wood harvesting business has led to rapid changes in the way these operations are organised. Advances in forest harvesting machines with today’s mechanised systems have been instrumental in a development where 'contractors' take more responsibility for the harvesting operations and the forest companies are increasingly dependent on contracting businesses, i.e. not carrying out the actual forest work themselves.
In addition to organisational changes of work, the introduction of machines in the forest has altered the physical working conditions. The working environment is now much easier to control in order to reduce the traditional accident hazards. However, other hazards may still exist.
Several studies on workers in harvesting operations have been performed especially in North America, Oceania and the Nordic countries. Musculoskeletal disorders, psychosomatic complaints and hearing loss are the most common health complaints. Low back pain has been observed to decrease, while neck and upper extremity disorders have increased, probably due to the increasing mechanisation in forestry, and changes in working postures. Accidents happen more often during harvesting operations than transportation. However, regarding forestry transport, the most dangerous operations are repair and maintenance work, and climbing into and out of the cabin .
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- Personal telephone discussion between Mr. Kari Ojanen, FIOH, and Mr. Simo Jaakkola, Deputy Managing Director of the Trade Association of Finnish Forestry and Earth Moving Contractors on 'Machinery in Sweden', 2013-05-28.
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- Metsäteho Oy, 'Hakkuutähteen paalauksen ja paalien metsäkuljetuksen tuottavuus', (The baling and forestry transportation of the logging residues; in Finnish), Tutkimusraportti 179, 11.8.2004. Available at: 
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- Päätös puunkorjuun järjestysohjeista(The State decision on instructions for logging; in Finnish). Valtioneuvoston asetus 749/2001. Available at: 
- Sozialversicherung für Landwirtschaft, Forsten und Gartenbau, Ladungssicherung in Landwirtschaft, Forst und Gartenbau, Waldarbeit, 11/2005, version 1/2013, pp. 1-63. Available at: 
- Sozialversicherung für Landwirtschaft, Forsten und Gartenbau, Ladungssicherung in Landwirtschaft, Forst und Gartenbau. 2013, pp. 1-36. Available at: 
- ILO – International Labour Office, Safety and health in forestry work, ILO code of practice, Geneva, 1998. Available at: 
- Finnish Occupational Safety and Health Administration, Tapaturmat ja ammattitaudit (Accidents and occupational diseases, in Finnish), 2011. Available at: 
- FAII - Federation of Accident Insurance Institutions, Accidents at work sustained by wage earners, by professional category, Finland, 2011. Available at: 
- Klun J., Medved M., 'Fatal accidents in forestry in some European countries', Croatian Journal of Forest Engineering 28,no 1, 2007. Avaiable at: 
- Klun J., Medved M., 'Fatal accidents in forestry in some European countries', Croatian Journal of Forest Engineering 28, no 1, 2007. Avaiable at: 
- FIOH - Finnish Institute of Occupational Health, Työperäisten sairauksien rekisteri (Register of the occupational disease; in Finnish), 2012. Available at: 
- Trzesniowski, A., 'Wood Transport in Steep Terrain', Seminar on Environmentally Sound Forest Roads and Wood Transport. Proceedings FAO, 1998.
- Olli, E., 'Timber Transport', Encyclopedia of Occupational Health and Safety, Jeanne Mager Stellmann, Editor in Chief. International Labour Organisation, chapter 68. Forestry, 2011
- Timber Transport Forum, Road Haulage of Round Timber - Code of practice, 4th edition, 2012. Available at: 
- European Commission – DG Energy and Transportation, European Best Practice Guidelines on Cargo Securing for Road Transport, (no date available), pp. 78-82.
- Ruokolainen, M., Metsä- ja peltobioprosessien energian tuotantoprosessien työterveys- ja työturvallisuusriskien arviointi (Risk assessment of occupational health and safety of productions chains of forest and field bioenergy; In Finnish), University of Eastern Finland, Faculty of Science and Forestry Environmental Science, Master's Degree Programme in General Toxicology and Environmental Health Risk Assessment, June 2012. Available at: 
- Nephropathia epidemica (NE) in Scandinavia is a zoonosis caused by Puumala virus. The main animal reservoir is the bank vole. NE predominantly affects men. The clinical picture of NE in Scandinavia is similar to that of hemorrhagic fever with renal syndrome in other parts of the world, although NE generally has a milder course. The case-fatality rate is approximately 0.2%.
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Links for further reading
EU-OSHA – European Agency for Safety and Health at Work, Safe maintenance in agriculture, Factsheet 99, 2011.. Available at: 
EU-OSHA – European Agency for Safety and Health at Work (no date). Maintenance and work-related transport safety, E-fact 26. Retrieved on 31 May 2013, from: 
EU-OSHA – European Agency for Safety and Health at Work (no date). Safe maintenance: Working with contractors and subcontractors, E-fact 62. Retrieved on 31 May 2013, from: 
EU-OSHA – European Agency for Safety and Health at Work, Checklist for the prevention of manual handling risks, E-fact 44. Retrieved on 31 May 2013, from: 
EU-OSHA – European Agency for Safety and Health at Work, ´E-facts 14 - Hazards and risks associated with manual handling in the workplace, from: 
The Finnish Forest Research Institute (24.05.2013). Home page. Retrieved on 30 May 2013, from: 
Forestry Research Institute of Sweden (no date). Home page. Retrieved on 30 May 2013, from: 
Norwegian Forest Research Institute (no date). Home page. Retrieved on 30 May 2013, from: 
The Nordic Forest Research Co-operation Committee (SNS) (no date). Home page. Retrieved on 30 May 2013, from: 
Guide to good practice in contract labour in forestery, Report of the UNECE/FAO Team of Specialists on Best Practices in Forest Contracting Food and Agriculture Organization of the United Nations, (2008. Available at: 
Gellerstedt, S., Lidén, E., Bohlin, F., Health and Performance in Mechanised Forest Operations, A handbook produced by ErgoWood, a project co-financed by the EUROPEAN COMMISSION, 2005. Available at: 
Gellerstedt, S., Eriksson, G., Frisk, S., Hultåker, O., Synwoldt, U., Tobisch, R., Weise, G., European ergonomic and safety guidelines for forest machines, A handbook produced by ErgoWood, a project co-financed by the EUROPEAN COMMISSION, 2006. Available at: 
Tobisch, R., Hultåker, O., Walkers, M., Weise, G., Improvements of ergonomic assessment procedures for forest machines– A comparative evaluation of three established test methods, The Swedish University of Agricultural Sciences, Report No 21, 2005. Available at: 
Walker, R., Tobisch, R., Weise, G., The Machine Operator Current Opinions and the Future Demands on Technical Ergonomics in Forest Machines, SLU, Institutionen för skogens produkter och marknader, Report 4., 2005. Available at: 
Lidén, E., Benchmarks for good work organization and successful implementation processes – Background to and working process of WORX, The Swedish University of Agricultural Sciences,2005. Available at: 
Vik, T., Working conditions for forest machine operators and contractors in six European countries, The Swedish University of Agricultural Sciences, Report 25, 2005. Available at: 
Østensvik, T., Cuchet, E., Veiersted, K., Vik, T., Nilsen, P., Lamiscarre, J., Bigot, M., Johansson Hanse, J., Carlzon, C., Winkel, J., Work exposure and complaints in a sample of French and Norwegian forest machine operators – A comparative field study within the ErgoWood programme, The Swedish University of Agricultural Sciences, Report 26, 2005. Available at: 
Nilsson, M., Health and Performance in Mechanised Forestry, Workshop on Sustainable Development of Competitive Forest Operations in Europe, Output from ErgoWood: Quality of Life and Management of Living Resources, 2005. Available at: 
COMFOR-Ergonomic tools for contractors, A method for continuous development and seven tools to facilitate this work, 2009. Available at: 
Axelsson, S.-Å., ‘The mechanization of logging operations in Sweden and its effect on occupational safety and health’. Journal of Forest Engineering, 9(2), 1998, pp. 25-31.
Backström, T., & Åberg, E., Olycksfall, in: J. Winkel, Attebrant, M., & Wikström, B.-O., (ed.), Konsensusrapporter rörande kunskapsläget om arbetsmiljön i skogsmaskiner, Arbete och Hälsa, 10, 1998, pp. 42-46.