My shoe soles are slippery, what can I do?

The soles on newly bought shoes may be slightly slippery due to the silicone residue left by the impregnating agent. You can roughen the sole slightly to counteract this (e.g. with sandpaper, on loose chipping or asphalt). Good rubber will become hardened on the surface by doing this. Repeat this process from time to time as required.