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Friction, Footwear and Falls

Published: 11th Aug 2016

Slips, trips or falls on the same level (STFL) rival manual handling injuries as the most common cause of non-fatal major injuries to employees. Solutions are often inexpensive, easy to devise and put in place and their benefits are considerable.

Although the scale of the problem has been recognised over several decades, STFL still persist as a major source of workplace injuries.

STFL have received the concerted attention of safety researchers, with progress made in understanding their mechanisms and circumstances. The complexity of the interacting causal factors, however, intrinsic and extrinsic, and close to or upstream from the injury genesis, presents a considerable challenge in designing and implementing effective prevention strategies.

They need to be part of a health and safety management system that includes regular inspection, maintenance and good housekeeping.

When they occur, investigation will often expose failures in the system as well as primary causes of the incident.


Falls on the same level, on stairs and from heights are endemic throughout society, afflicting all ages. Likewise, falls occur widely during home and leisure pursuits as well as those related to work. In this article the focus will be limited to the discussion of occupational STFL as a particular class of injuries.

The distinction between occupational and non-occupational slips, trips and falls, and falls on the same level versus falls on steps and stairs or from heights, is significant when incidents are considered from a systems perspective. Different causal factors are dominant in occupational slips, trips and falls compared with falls among the elderly, for example, with different patterns of causation leading to different approaches to prevention.


Slipping occurs when the friction between the foot or shoe sole and the floor surface provides insufficient resistance to counteract the forward or rearward forces that occur during the stepping process, i.e. interaction between human (foot or shoe sole) and floor.

Three categories of slips when walking based on the length of slip were described by Leamon and Li (1990): a ‘microslip’ is a slip shorter than 3cm, a ‘slip’ is as long as 8-10cm, and a ‘slide’ describes the uncontrolled movement of the heel, which typically arises when a slip length exceeds 10cm.

Microslips generally pass unnoticed; a slip will result in instinctive efforts to regain postural control; while a slide is likely to lead to loss of balance resulting in a fall. A trip occurs when the swing phase of the foot is interrupted unexpectedly due to inadequately clearing the ground. Irregularities of as little as 5mm in the walking surface may be sufficient to cause a trip.

Loss of balance leading to falls can also arise due to unexpected, forcible contact with something or someone. Similarly, unexpected, forcible movement of the floor, as may happen when standing in a moving vehicle, may cause a loss of balance sufficient to result in a fall on the same level.


It is appropriate to comment on the limitations with available data. Such data, whether collected as part of national, industrial sector or company occupational injury monitoring systems that vary and are necessarily restricted in their categories. Distortion of data that can arise with reporting schemes requiring classification of an incident into a restricted number of groupings, compounded further by coding choices having to be made by registration personnel based on their subjective judgements. Analysis by Strindberg (1983) found that slipping and falling incidents have been seriously underestimated with the reporting scheme applied in Sweden at the time.

Some incidence reporting schemes may fail to differentiate between falls on the same level and falls from height (Lortie and Rizzo, 1999). With the most recent occupational injury data available in Great Britain, for example, ‘slips, trips and falls on the same level’ and ‘falls from height’ are presented and discussed together as ‘slips, trips and falls’, as the information collected does not allow a consistent distinction to be made between them (Health and Safety Executive, 2014). Another point to note is that variation exists in the precise classifications used by different reporting schemes for incidence data relevant to STFL. The variation in the terminology in the following sections reflects that used by different reporting agencies and researchers.

Scale of the issue

The European Commission (2008) presented an analysis of 3,983,881 non-fatal accidents at work occurring during 2005, involving more than three work days absence. Of these, ‘slipping – stumbling and falling – fall of person – on the same level’ was the largest category, amounting to 14.4%. A further 4.4% were recorded as ‘treading badly, twisting leg or ankle, slipping without falling’. In the US, data from the Bureau of Labor Statistics (BLS) (2014) showed that among 1,162,210 non-fatal occupational accidents and diseases recorded in 2013 at private companies and government agencies, 17.4% were a fall on the same level resulting in a median 10 work days lost.

A further 4.4% of the reports were slips or trips without a fall but leading to an injury (e.g. back injury), resulting in a median 11 work days lost. Thus, two important data collection agencies indicate that STFL internationally amount to approximately one in five of reported non-fatal work-related accidents. Reliable occupational injury data are only available for a limited number of countries, but the data that do exist indicate that occupational injury rates are much greater in countries beyond those classified as ‘established market economies’ (Hämäläinen, Takala, Saarela, 2006). Even with the caveats that apply in extrapolating data available from industrially developed countries, we can be content that the global toll of injury from STFL is immense.

Injury outcomes

Fortunately, fatalities are a rare consequence of STFL. Nevertheless, Buck and Coleman (1985) emphasised that injuries from STFL are far from trivial, with 17% of those in their examination of published data on workplace accidents in Great Britain resulting in fractures. A further 17% were classified as ‘contusions and crushing’ and 36% as ‘sprains and strains’. Bentley and Haslam (1998), in a study of postal delivery workers working outdoors, found that the ankle was the most frequent site of injuries (23%), followed by the knee (17%) and back (16%).

They also found that almost 50% of days lost were due to ankle and back problems; ankle injuries resulted most often from trips and back injuries from slips. For US workers experiencing injuries requiring days away from work, Yeoh, Lockart, and Wu (2013) found that extremities, which included the knees, feet and toes, were the most affected body parts injured in falls on the same level, comprising 30.7%. The trunk, which included shoulder and back, was the second most injured at 25.6%. Workers with multiple injured body parts ranked third with 21.8% of overall injuries.

In the industrial environment, back injury is the most frequent cause of workers’ compensation claims in the United States (Guo et al , 1999). The prevalence of lower-back pain in a lifetime has been reported to be between 55% and 87% (Videman et al , 1984; Riihimäki, 1985). Lower-back pain has been shown to be associated with slips and falls (Rohrlich et al . 2014). Epidemiological studies have indicated that sudden loading to the trunk is associated with acute lower-back pain and may be a primary risk factor for chronic lower-back pain development (Manning and Shannon, 1981; Manning, Mitchell, Blanch eld 1984; Rohrlich et al , 2014). Courtney et al (2001b) suggested that one workers’ compensation provider claimed that the cost ratio for ruptured discs due to same level falls was highest (13.3) among many injury claims (cost ratio is the ratio of the average cost of the particular injury to the average cost of all injuries for that particular class of falls).

Unexpected gait perturbations can be dangerous to the lumbar spine because of the rapid corrective movements needed to regain balance (Liu, Lockhart, Kim, 2014). Trunk acceleration can increase significantly during unexpected perturbation, such as slipping, compared with that during normal gait (Hirvonen et al , 1994; Ehsan et al , 2013).

Primary prevention

The purpose of primary prevention is to eliminate STFL hazards at source through the design of the work environment and work/activity systems. Flooring should be selected with appropriate slip resistance for the different conditions to which it will be subjected. Walkways and walking areas should be designed and constructed to avoid trip hazards. In addition, primary prevention involves attention to the equipment used (e.g. to avoid spillages and other walkway contamination), the manner in which equipment is arranged, the tasks workers need to perform, and the extent to which each of these elements might affect the risk of falling.

Provision of sufficient, accessible storage is a measure aimed at reducing the need for objects and materials to be placed in the walking path, which may then present a trip hazard. The provision of sufficient lighting is important to aid visibility of the walking surface. The design and installation of walking surfaces and pathways should make allowances for their cleaning and maintenance. In addition, to avoid introducing hazards by wear and tear, installations should be appropriately durable and resistant to damage. Pedestrian walkways can be protected from vehicle intrusion or damage; for example, by ensuring there is physical separation between the two such as through the installation of bollards.

Risk reduction

Even with concerted attention to primary fall prevention, it is inevitable that STFL hazards will continue to be present in the environment. Risk reduction aims to reduce the likelihood of STFL and injuries arising from these hazards. An important starting point is to raise awareness of the problem and, through education, promote understanding of risk factors for falling and how they can be mitigated. Accompanying this is a need for proactive risk assessment and management.

Where STFL hazards may arise in an area used by pedestrians, it is important that adequate procedures are implemented to detect these hazards and to remedy the situation. Indoor flooring will usually need to be cleaned periodically for the sake of hygiene and appearances. Care should be taken during the cleaning process to make sure STFL hazards are not introduced; for example, the risk of slipping on wet vinyl or tiled floors while these surfaces are drying. For maintenance, routine inspection programmes should be arranged for walking areas and pathways. In all cases, housekeeping procedures should be designed to be sustainable so that initial good practices do not deteriorate to the point of becoming ineffective, as can readily occur over time.

Where STFL hazards are present and cannot be removed immediately, an obvious action is to warn of their existence. This can be done through the use of signage warning of a risk of slipping. Lighting may be adequate, but is only effective if turned on at appropriate times. Carrying items and hurrying are additional behavioural factors contributing to STFL and should be discouraged in circumstances where other STFL risk factors are present. These behavioural factors often reveal more upstream organisational and cultural factors (Leclercq, 2014).

There are certain conditions in which risk of STFL is increased. Poor weather, resulting in outdoor areas becoming covered with ice or snow, is frequently accompanied by increased prevalence of slip-induced falls, unless appropriate precautions have been taken. It should be possible to plan ahead for such occasions and facility managers ought to be ready and prepared to implement measures to reduce risk, either through clearing affected areas or by reducing exposure to the slippery conditions (e.g. by temporary changes to working practices which keep workers indoors).


Although there is increasing recognition of the complexity of the interacting factors in STFL and the need for multi-disciplinary approaches, systems perspectives adopting a more holistic view of STFL causation are immature. Further work is needed, drawing on current developments in socio-technical systems thinking and safety. Greater attention is necessary to the factors upstream in the injury genesis forming the circumstances in which injuries occur. It is important to consider these upstream factors in STFL prevention.

Published: 11th Aug 2016 in Health and Safety Middle East

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Toby Hayward
Mr. Hayward has worked in various high-risk industries including nuclear, offshore and deep sea. Having also been a corporate leader of health and safety in international companies he has spent more than 20 years advocating for sensible risk culture both in the Middle East and Globally