JMHO....I think it will be slippery, especially if it gets wet. I do love travertine though.

all floors are slippery when wet. Even the rougher tiles used around swimming pools.

I have some very rough tile designed to be antislip. It grabs more dirt and dust than any other floor. It requires more work to clean. It reduces socks to rags very fast.

I also love real stone. We settled for a porcelain NOT highly polished tile in our kitchen because everything I read about polished trav on floors told me I'd be insecure, and that's no way to feel in the kitchen. And I'm not a person who falls easily, so if you already fall I would surely advise against polished stone. On the other hand, davidrol's antislip tile sounds like a lot to put up with. Good luck making your choices!

Ask to see the rating (it might be called viscocity? Or that could be completely wrong, LOL). This was a big concern to me a couple of years ago when we redid the floor in our master bath, and in our kitchen because we have a pool. A floor store helped me understand that all tile is rated for slipperyness when wet. I have forgotten the scale, but any decent floor store should be able to tell you.

Polished travertine wouldn't be suitable for most people for a kitchen floor regardless of whether or not it was slippery. It's relatively soft and porous nature which leads to scratching, staining and etching would show every bit of patina on a polished surface. It'd be OK for honed, if you were OK with a more "lived in" look, but polished would be a nightmare for most to actually live with as flooring. Add in the slipperyness factor that you are worried about, and you really need to move on to a different choice for your floor. Perhaps a honed version would work for you if you are OK with the maintainence needs.

With floor tile it is usually the grout lines that give you some 'tooth'. An 18" polished tile will be slippery...beautiful, but slippery.

I agree with live_wire_oak. Polished travertine will look terrific for a few weeks. But sooner or later, it's going to get scratched, and within a year or two, you'll start seeing wear paths in the stone, where it's not nearly as shiny as the rest of the floor. I you're going to do travertine, use a honed stone. I still don't recommend it (because of staining and so forth-- rectified porcelain lookalikes are so much easier to keep pristine), but it'll stay in good condition alot longer.