`Walking-Mode Maps', based on Slip/Non-Slip criteria, are proposed. Slip/Non-Slip criteria are expressed as follows:
• for a slip to occur: |F<sub>h</sub>/F<sub>n</sub>|<sub>h</sub> ≥ μ<sub>s</sub> or |F<sub>h</sub>/F<sub>n</sub>|<sub>t</sub> ≥ μ<sub>s</sub>
• for no slip to occur: |F<sub>h</sub>/F<sub>n</sub>|<sub>h</sub> < μ<sub>s</sub> or |F<sub>h</sub>/F<sub>n</sub>|<sub>t</sub> < μ<sub>s</sub>
|F<sub>h</sub>/F<sub>n</sub>|<sub>h</sub> and |F<sub>h</sub>/F<sub>n</sub>|<sub>t</sub> are the maximum peak value of the traction coefficient at heel-strike and toe-off respectively, and μ<sub>s</sub> is the static friction coefficient between shoe sole and walkway. The `Walking-Mode Map' for the level-surface shows the possible regime of each walking mode as Slip, Slip possible or No slip. Our results, which are based upon a small population and strictly-specified test conditions, indicate that a static friction coefficient higher than 0.47 will prevent both forward and backward slips under our test conditions and under a range of step lengths of 0.55 to 0.95 m and walking speeds of 1.0 to 1.9 m/s. We also found that shorter steps reduce the chance of a slip. A `Walking-Mode Map' for inclined-surface ambulation has also been developed. The inclined-surface results show the friction and inclination-angle-related regime of each walking mode: Slip, Forward slip at heel-strike phase in descending, Backward slip at toe-off phase in ascending, or No slip. Again, extreme caution must be taken in generalizing these small-sample results (n=1, for the inclined tests) to the general population.