I have an old pair of Clark's sandals. They are comfortable, and the uppers are fine, but the original tread on the soles had worn down to a high gloss. The other day I slipped, and decided they were no longer safe to walk in.
Given the fine condition of the uppers, I took the pair along to out local Timpson's, to see if they could be re-soled. The guy sucked his teeth and looked dubious. They probably wouldn't take a re-soling. We discussed it for a bit, and I explained I just needed the soles made less slippery. He said he would try "roughening them up" on the machine.
Several minutes and a strong smell of buring rubber later, he returned them to me, with a lovely lattice of grooves carved into the previously smooth soles:
Timpson's for the win, again.