Slips and falls are a major problem in occupational injuries in which floor slipperiness is a critical issue. Friction variation is speculated to be a significant contributor to slip and fall incidents, although it has not been quantified and related to a measurement of slipperiness. A friction variation study is more valid when conducted in a field environment. This study investigated friction variation in six major working areas of a fast-food restaurant in the USA. The results indicated that there was slightly more than a 50% chance that employees might experience a friction reduction when stepping from one foot to the other while walking in the major working areas studied. The absolute reduction in friction coefficient had an average and standard deviation of 0.12 and 0.15, respectively. The relative reduction in friction coefficient had an average and standard deviation of 0.19 and 0.22, respectively.