Identification and evaluation of slip and fall risk on ice and snow

Sammanfattning: Roads and pavements covered with ice and snow during winter in the Nordic and other cold regions are slippery, which result in the prevalence of slip and fall accidents among not only the public, but also outdoor workers. Literature and injury statistics revealed that the most frequently specified contributory factor for occupational slip, trip and fall accidents in Sweden is snow and ice. Road accident research showed that the largest numbers of traffic casualties occurred during walking, followed by cycling and vehicle transporting. The cost to the community of providing medical treatment to victims of pedestrian injuries resulting from slipping is far greater than that of keeping walking surfaces free from ice and snow. However, in comparison with the size of the problem, little research has been carried out to identify and evaluate slip and fall risk on icy surfaces. Objectives are to present a systems perspective of slip and fall accident, to measure, evaluate and compare the coefficient of friction (COF) of footwear on ice and lubricated floor, to identify advantages of walking experience on icy surface and participating in winter sport in preventing slip and fall accidents, to develop subjective evaluation method for slipperiness measurement and usability assessment of footwear product, to systematically assess the integration of slip resistance, thermal insulation, and usability of footwear, to ascertain the anti-slip effect of materials spread on ice by user trials, and to explore the incorporated approach towards the design of footwear for use on icy surfaces. The following methods of collecting data were used in studies of this thesis: 1) direct observation, 2) videotaping, 3) human perception rating scale, 4) objective COF measurements, 5) retrospective cross-sectional epidemiological study by questionnaire. a systems model involving potential factors was proposed based on a comprehensive literature review (study I). Comparison of objective evaluation of footwear slipperiness on ice and oily floor was used to examine the frictional performance on different underfoot surfaces (study II). Epidemiological survey of slip and fall accidents was carried out focusing on individual experience, winter participation, severity of injuries, footwear, and underfoot surface conditions (study III). Subjective rating scale was developed and used to assess the perception of slip and fall risk and the usability of footwear used on various icy surfaces including anti slip materials spread on ice (study IV). The integration of multiple protection function and usability into winter footwear was also assessed (study IV). A systematic analysis of the slips and falls on icy and snowy surfaces showed that the etiology of slips and falls is multi-faceted. The COF on ice by objective measurements at 0ºC is much lower than that at -12ºC and that on stainless steel. Polyurethane soling material did not provide sufficient friction on wet ice at least when new (without abrasion), although superior on lubricated floors. The footwear tested including winter footwear, professional footwear, safety footwear, and footwear deemed to be slip resistant by users and manufacturers did not provide sufficient protection against slips and falls on wet ice at around 0ºC. Accordingly, slip and fall risk is higher on wet ice than on dry ice and lubricated floor. Slip and fall events reduced with increased living experience in cold environments and winter sport participation. Newcomers with no or less experience were prone to falling, and therefore they should be well informed of potential slip and fall hazards upon arrival in cold region. Slip resistance, thermal insulation and usability of footwear tested were not properly integrated. In addition to thermal insulation, prevention of slip and fall hazard by improving anti-slip property and usability must also be priorities for development of footwear for use in cold environments. Based on the findings, anti-slip footwear, measurement methods for slipperiness on ice and snow, related standards, the role of gait biomechanics and task-related factors should be further developed and studied.